The Maui County
Hazard Mitigation Plan
Prepared By:
Pamela Pogue
Rhode Island Emergency Management Agency
And
Robert J. Collum Jr.
Maui County Civil Defense Agency

TABLE OF CONTENTS

I. INTRODUCTION 
Cost of Disasters 
Hazard Mitigation Defined 
Benefits of Multi-natural Hazard Mitigation 
Sustainable Communities 
GOAL 11: Cultural Awareness 

II. PLANNING PROCESS 

III. MISSION & GOALS OF THE MAUI HAZARD MITIGATION STRATEGY 

Mission
Goals 
Methodology 
Maui County Geography and Demographics 
Response Agencies 
Maui “Project Impact”

IV. HAZARDS IDENTIFICATION AND ANALYSIS 

Hydrologic Hazards 
Floods 
Coastal Storms
Stream Flooding 
Coastal Flooding 
Dam Breaks 
Landslides/Debris Flows 
Coastal Erosion 
Natural Course of a Beach Lifecycle
Coastal Erosion vs. Beach Erosion
Effect of Local Wind and Surf Patterns
Sediment Deficiencies
Past and Recurring Damage
Wind Hazards 
Wind Pressure
Wind Speed 
Wind Patterns 
Hurricanes 
Kona Storms 
Seismic Hazards 
Earthquakes 
Tsunamis 
Drought 
Wildfire 

V. HAZARD RISK AND VULNERABILITY ASSESSMENT

Risk and Vulnerability Assessment Defined 
Social Vulnerability 
Environmental Risk and Vulnerability 
Critical Facilities Risk and Vulnerabilities 
Specific Flood Risks and Vulnerabilities
Specific Coastal Erosion Risk and Vulnerabilities 
Specific Wind Hazard Risk and Vulnerabilities 
Specific Seismic Hazard Risk and Vulnerabilities 
Specific Drought Risk and Vulnerabilities 

VI. MITIGATION ACTIONS AND PROJECTS

STAPLEE 
Mitigation Action for Flooding p. 
Mitigation Actions for Coastal Erosion 
Mitigation Actions for Wind Events 
Mitigation Action for Seismic Events 
Projects 
VII. IMPLEMENTATION 

VIII. PLAN MAINTENANCE 
LIST OF ACRONYMS
GLOSSARY
REFERENCES
APPENDICES
Project Impact – County of Maui
Maui County Council Resolution
County of Maui Proclamation by Mayor Alan Arakawa
FEMA Letter of Acceptance

Chapter I Introduction
“The most recent disaster fades from memory just before the next one strikes...”
Ancient Japanese Proverb

The Cost of Disasters
Property damage resulting from natural hazards has become exceedingly costly, for
both the disaster victims, and the American taxpayer. From 1989 to 1993, the
average annual loss from natural disasters was $3.3 billion nationally, the past 4 years
has seen that amount increase to 13 billion annually. (FEMA, IS393, April 1998) Over
6,000 people have been killed and 50,000 injured from natural disasters in the past 25
years. (FEMA, 1998)

The second most active hurricane season in the Pacific on record in the United States
occurred in 1995. There were a total of 19 named storms, 11 reaching hurricane
strength. The end result was 58 people dead and more than $5.2 billion in property losses.
Aside from the direct costs, or those damages and losses directly attributable to the disaster,
Americans also suffer from indirect costs, most of which may take much longer to recover
from. Direct costs are short term and may include such costs as tree removal, setting up
an emergency shelter, debris removal and the cost of repairs to public, private and
commercial sectors. Indirect costs are those incurred sometime after the event, perhaps six
months or more. These long-term costs include the permanent loss of employment, loss of tax revenues from business
relocation health expenses incurred from a permanent injury or counseling to deal with
the loss of a loved one.
Recovery from disasters requires resources to be diverted from other public and
private programs, adversely affecting the productivity of the economy. Business
interruption insurance only covers a small part of actual losses. Loss of economic
productivity and downtime in tourism not really accounted by the public or private
sector.

Costs of Disasters in Hawaiian Islands
1959 - present
Date Disaster Location Amount of Damage*
9/10-11/92 Hurricane Iniki Kauai, Hawaiian Islands $ 1.6 billion
11/23/83 Hurricane Iwa Kauai, Oahu $239 million
1/8-10/80 Kona Storm Maui $ 12.9 million
5/23/60 tsunami Hilo, Hawaii $ 23 million
8/4-6/59 Hurricane Dot Kauai, Hawaii, Oahu $ 6 million (Kauai)
4/1946 tsunami Hilo, Hawaii $ 2.6 million
*Dollars given in the year damage occurred

What is Hazard Mitigation?
Hazard mitigation is action taken to permanently reduce or eliminate long-term risk to
people and their property from the effects of natural hazards.
As the direct and indirect costs of disasters continue to rise, it becomes particularly
critical that preparing for the onslaught of damage from these events must be done in
order to reduce the amount of damage and destruction. This strategy is commonly
known as mitigation. The purpose of multi-hazard mitigation is twofold: 1) to protect
people and structures from harm and destruction; and 2) to minimize the costs of
disaster response and recovery. Hazard mitigation planning is the process that
analyzes a community’s risk from natural hazards, coordinates available resources,
and implements actions to reduce risks. (Tennessee Emergency Management
Agency).
To ensure the national focus on mitigation, the Federal Emergency Management
Agency (FEMA) introduced a National Mitigation Strategy in 1995. The National
Strategy promotes the partnership of government and the private sector to “build”
safer communities. Hazard mitigation encourages all Americans to identify hazards
that may affect them or their communities to take action to reduce risks.
Mitigation Benefits
Mitigation actions help safeguard personal and public safety. Retrofitting bridges, for
example, can help keep them from being washed out, which means they will be
available to fire trucks and ambulances in the event of a storm. Installing hurricane
clips and fasteners can reduce personal and real property losses for individuals and
reduce the need for public assistance in the event of a hurricane. Increasing coastal
setbacks reduces the risk of deaths and property losses from tsunamis and storm
surge. Increased setbacks also reduce the risk of property losses from coastal
erosion.
Another important benefit of hazard mitigation is that money spent today on
preventative measures can significantly reduce the impact of disasters in the future,
including the cost of post-disaster cleanup.
Formal adoption and implementation of this strategy will help Maui gain credit points
under the Federal Emergency Management Agency’s (FEMA) National Flood
Insurance Program (NFIP) Community Rating System (CRS). CRS provides
discounts on flood insurance premiums for property owners in communities that
participate in this voluntary program. For example, points are given to municipalities
that form a Local Hazard Mitigation Committee (LHMC). Communities also receive
points if they involve the public in the planning process, coordinate with other agencies,
assess the hazard and their vulnerability, set goals, draft an action plan (local hazard
mitigation strategy), and adopt, implement and revise the plan.
There are many categories to gain credit for public education and awareness activities
regarding floodplain management and mitigation. Non-federally owned open space
land in floodplains can also help a municipality gain credit points under the CRS program. In
addition, vegetated open-space land enhances the natural and beneficial functions
that floodplains serve and helps prevent flood damage.
The adoption of this mitigation strategy will enhance Maui’s eligibility for federal
grants, which include FEMA’s pre-disaster Flood Mitigation Assistance Program
(FMAP) and its post-disaster Hazard Mitigation Grant Program (HMGP). Pre-disaster
planning will also help post-disaster operations become more efficient. For instance,
procedures and necessary permits can be identified prior to the disaster and therefore,
permit-streamlining procedures can be put into place. Priorities for mitigation during
reconstruction can also be identified, helping to reduce the high costs of recovery after
a disaster. The state emergency response effort will run more smoothly because of
the guidance provided in this strategy.
Perhaps the most important benefit from a county hazard mitigation strategy is that it
will minimize the social and economic disruption from multiple hazards. One need only
look at the impact that Hurricane Iniki had on the people of Kauai. Unemployment six
months after the storm was running at over 16 percent. (Pers. Comm. Mike Hamnett,
October 9, 2000) Six years after the storm, several hotels had not reopened and until
the recent upturn in tourism, Kauai’s economy was lagging significantly behind the rest
of the State. (Pers. Comm. Hamnett, October 9, 2000)
Maui County Emergency Managers Sustainable Communities
A resilient community is one that lives in harmony with nature’s varying cycles and
processes.
David Godschalk, Timothy Beatley, et al
“Disaster resilient” communities employ a long range, community-based approach to
mitigation. Mitigation advocates communities to proactively address potential damage
that could occur from hurricanes, coastal erosion, earthquakes, flooding and other
natural hazards. When natural hazard mitigation is combined with the standards of
creating sustainable communities, the long-term beneficial result is smarter and safer
development that reduces the vulnerability of populations to natural disasters while
reducing poverty, providing jobs and promoting economic activity, and most
importantly, improving people’s living conditions (Munasinghe and Clarke 1995). In
addition to community sustainability’s criteria of social, environmental and economic
protection, there is also the criterion that development must be disaster resistant
(Institute for Business and Home Safety 1997).
Resilient communities may bend before the impact of natural disaster events, but they do not
break. They are constructed so that their lifeline systems of roads, utilities, infrastructure, and
other support facilities are designed to continue operating in the midst of high winds, rising water
and shaking ground. Hospitals, schools, neighborhoods, businesses and public safety
centers are located in safe areas, rather than areas prone to high hazard. Resilient and
sustainable communities’ structures are built or retrofitted to meet the safest building code
standards available. It also means that their natural environmental habitats such as
wetlands and dunes are conserved to protect the natural benefits of hazard mitigation
that they provide.
The Maui County Hazard Mitigation Strategy advocates the concepts of disaster
resilient and sustainable communities. Maui is committed to building a disaster
resistant community and achieving sustainable development through the commitment
of County government and its policymakers to mitigate hazard impacts before disaster
strikes. Additionally, Maui will achieve a disaster resilient, and therefore, safer
community, through the process of completing its Hazard Risk and Vulnerability
Assessment (RVA), and Multi-Hazard Mitigation Strategy (HMS) and through the
implementation of mitigation programs and policies. The County will have the
capability to implement and institutionalize hazard mitigation through its human, legal
and fiscal resources, the effectiveness of intergovernmental coordination and
Hawaii Coastal Zone Management Booth at the Project Impact Fair in Hana 
communication, and with the knowledge and tools at hand to analyze and cope with
hazard risks and the outcomes of mitigation planning.

Goal 11: Cultural Awareness
Established in 1993, the President’s Council on Sustainable Development set forth
new goals for sustainable development. These ten goals – Health and the
Environment; Economic Prosperity; Equity; Conservation of Nature; Stewardship;
Sustainable Communities; Civic Engagement; Population; International Responsibility;
and Education – are interdependent and essential towards realizing economic
prosperity, environmental protection, and social equity. However, the Council
overlooked Goal 11 . . . . . Cultural Awareness.
It is essential to consider culture regardless, particularly when “sustainability” in the
context of the economy, environment, population, or even the resiliency of
communities towards natural disasters. Culture is a key thread that binds the very
fabric of these and other goals together. Across the nation and throughout the world,
lessons are being learned from aboriginal peoples with respect to land use, watershed
management, marine and terrestrial conservation, and sustainability based on the
respect and balance between man and nature. Today, the term “cultural profiling” has
become a new buzzword in the planning and decision-making process. No longer will
federal, state, and county governments be discussing projects and programs in a
culturally sterile vacuum.
In ancient as well as contemporary Hawaii, Hawaiian people shared a unique
relationship with their environment. It is a symbiotic relationship based on a physical
and spiritual bond that developed enduring socio-cultural values, beliefs, and
practices. On a spiritual level, it was believed by the ancient Hawaiians that both man
and the earth were born from the same spirit world.  As such, a physical respect for the 
environment was shown by the way Hawaiians approached the use of animate (i.e., plants, birds, fish) 
as well as inanimate (i.e., stones, water, rain) resources.
Permission and guidance was always sought from the gods, ancestors, and a people’s council (Aha
Ki’ole) consisting of skilled practitioners knowledgeable in medicine, agriculture,
weather, astronomy, as well as many other specialties. Through these physical and
spiritual “checks and balances”, “pono” or “to make things right” could be maintained
between man and his environment.
Examples of these “checks and balances” can be experienced through ancient
Hawaiian beliefs that have been passed down through “oli” (chant) or “mo’olelo”
(stories). For instance, Hawaiian people have a saying – “He kiu ka pua kukui na ka
makani” – used to describe the falling of kukui blossoms as a sign of the coming of
strong winds. This proverb demonstrates the observant nature of the ancient
Hawaiians with respect to their environment. The Kukui blossom was a sturdy flower
that required tremendous effort to dislodge. As such, during winter months the falling
of Kukui blossoms was nature’s sign of an approaching storm or hurricane. The
Hawaiians, being practical people, would insure that their homes had secured
lashings, personal belongings were stowed, and that other necessary precautions
were taken.
The Hawaiians also studied the behavior of animals such as the wild boar. “Kakaika
pua pua’a i ka malie he ino” meant that a storm was approaching if you observed a
herd of wild boar running in a single file. Again, it is this idea of being a part of nature,
rather than conquering it.
Ancient sustainable practices such as (1) stream clearance to prevent flooding and to
insure the consistent flow of water and nutrients to agricultural fields and ocean
fishponds; (2) reforestation to protect watersheds and natural systems; and (3)
beneficial land use practices through the implementation of ahupua’a (land divisions)
governed by people’s councils insured the pono or balance between man and nature.
These practices were done not because you had to do them, but because it was the
right thing to do with respect to benefiting the community rather than one’s self.
Other rational practices that maintained this natural balance consisted of the
construction of temporary coastal villages that would be used for fishing during the
summer months and later abandoned as winter’s inclement weather approached the
islands. Even the ancient Hawaiians knew when to practice coastal retreat.
Permanent settlements were constructed out of the natural flood plain areas and
individual homes were elevated on stone platforms and built into the forested areas in
order to mitigate the energy of storms and hurricanes.
So what can we learn from all of this? The answer is . . . . . “As much as we can.”
There are definite lessons that can be learned from our cultural past. However,
physical lessons alone are not enough to build sustainable communities. A
restructuring of public values and attitudes need to be perpetuated in order to
accomplish sustainable goals and to build hazard resilient communities that rely not
only on hard, structural solutions, but natural, ecological protective measures that are
based on traditional knowledge and scientific study.

Chapter II Planning Process
Process
The development of the Maui Hazard Mitigation Strategy began during the Maui Project
Impact grant period. The Maui County Project Impact Coordinator invited directors and
staff from public agencies, private businesses and organizations, and community
representatives to participate in the various committees with several of these
participants serving as members of the Steering Committee, Education & Awareness
Committee, Business & Industry Committee, Technical Standard Committee, Hana/East
Maui Committee, and Lahaina/West Maui Committee. Pacific Disaster Center provided
technical support to all committees. Project Impact Community Partners are noted at
the end of this chapter. Additional information on Maui Project Impact activities related
to the planning processes is located in Appendix A. The goal of developing a hazard
mitigation strategy for Maui County has remained constant. This chapter describes the
planning process.
Planning Approach and Methods
Maui County also participates actively in the State Hazard Mitigation Forum, helping to
guide hazard mitigation planning and activities in the State while receiving guidance
from the Mitigation Planning Committee, The Multi-hazard Scientific Advisory
Committee and other committees.
The methods used in the hazard mitigation planning process have been drawn from
several sources. These include the process delineated in the NOAA Coastal Services
Center Community Vulnerability Assessment Tool: http://www.csc.noaa.gov/products/nchaz/
startup.htm. The Federal Emergency Management Agency’s guidance series, getting
started, Understanding Your Risks – Identifying Hazards and Estimating Losses and
developing the Mitigation Plan (FEMA 386-1, 2, 3) were referenced during the planning
process.
Elements of this process were developed over several years of hazard mitigation
preparedness and planning in the State of Hawaii. Maui County participated in the 1996
Coastal Hazard Mitigation Workshop, supported jointly by NOAA’s Office of Ocean and
Coastal Resources Management and FEMA Region IX. This workshop allowed counties
and jurisdictions to share ideas about hazard mitigation. Following this, the Statewide
Hazard Mitigation Forum was established in 1998. Maui County has had representation
from the Maui County Planning Department as a full member and the Civil Defense
Agency as an ex-officio member.
The Maui County mitigation strategy is multi-hazard in scope. It addresses wind hazards
(hurricanes and strong winds); hydrologic hazards (floods, coastal storms, stream
flooding, dam brakes, landslides); coastal erosion (beach lifecycle and erosion); seismic
hazards (earthquakes); tsunami, drought and wildfire.

The planning approach for Maui County involved the following:
• Briefed County Officials and invited participation from public and private
agencies, organizations and groups. Discussed process and gained agreement
on approach.
• Gathered available county asset data; used interviews and meetings to collect
data. Assessed data availability and condition of data. Gathered and reviewed
available hazard studies and assessments for Maui County.
• Used meetings to educate about hazard mitigation, risk and vulnerability and
planning process.
• Held public forums and meetings to get suggestions and ideas to address
problems. Incorporated these into the strategy.
• Met with the Disaster Mitigation Committee to review risk and vulnerability
assessment and strategy development. Established criteria for prioritizing
projects and programs.
• Set up maintenance plan to update strategy with new input, data, and
accomplishments.
• Adopted the strategy formally.
• Implement strategy. Begin projects. Review goals and objectives, revise
appropriately, and continue iterative process as needed.
Maui County fully intends to involve the general public for future iterations of its multihazard
mitigation through public forums, the State Hazard Mitigation website
(www.mothernature-hawaii.com), and the media. The Maui County Disaster Mitigation
Committee will be the key agency organizing and conducting those activities relating to
hazard mitigation planning. This body will be comprised of representatives from all
levels of government and the private sector.
The following is a timeline of the activities that led to the Maui County Multi-Hazard
Mitigation Strategy:
• March 1999 - Initial Project Impact Meeting
• April 5-7, 2000 - Project Impact Hazard Mitigation Workshop at Pacific Disaster
Center.
• June 15, 2000 - County Council Economic Development Committee.
Presentation by Will Orr, Prescott College, on “Growth Model with Hazard & Risk

Vulnerability Assessment.” Presentation by Pam Pogue on “Integrating Hazard
Mitigation on Maui County - Process and Planning.”
• June 28, 2000 - Meeting with EOC personnel and Pam Pogue to discuss start of
Plan. Representatives from the following departments of the County of Maui were
invited to this meeting: Managing Director, Economic Development, Finance,
Police, Fire, Public Works, Water Supply, Housing and Human Concerns, Parks
and Recreation, Corporation Counsel, Planning. Representatives from the State
of Hawaii: Civil Defense, Hawaii Air National Guard, District Health Services,
Engineering, Highways, Airports, Harbors, Human Services, Civil Air Patrol,
DMAT Hi-1, Department of Land and Natural Resources. The following
organizations were also asked to send a representative: Maui Pacific Center,
American Red Cross, NWS, Maui Economic Opportunity, RACES, Hawaiian
Telephone Company, Maui VOAD, American Medical Response, Maui Electric,
and Maui Memorial Medical Center.
• July 11, 2000 - Diane Zachary of Project Impact, Pam Pogue, Mike Hamnett and
Cheryl Anderson from the State Hazard Mitigation Forum and University of
Hawaii attended the Maui Planning Commission to explain Project Impact and
hazard mitigation.
• August 7, 2000 - Public Meeting in Maui County Council Chambers on overview
of hazard mitigation and processes occurring on Maui County by Pam Pogue.
• August 23, 2000 - Pam Pogue conducted a public meeting in the Maui County
Council Chambers to share findings of work in process, and the risk and
vulnerability assessment and to solicit public input on mitigation actions and
awareness.
• September 15, 19, 24 and October 6, 2000 - Akaku TV, Maui Public Access
Television, aired the August 23, 2000 public meeting by Pam Pogue.
• October 6, 2000 – Council of the County of Maui adopted “Resolution No. 00-140
SUPPORTING THE ESTABLISHMENT OF THE COUNTY OF MAUI AS A
DISASTER RESISTANT COMMUNITY THROUGH A COMPRHENSIVE
MITIGATION PROGRAM AGAINST NATURAL HAZARDS.” (Appendix B.)
• October 11, 2000 – Mayor of the County of Maui signs a Proclamation that
supports develops and implements a County Multi-Hazard Mitigation Program.
(Appendix C.)
• October 11-13, 2000 - Maui Project Impact held a statewide hazard mitigation
institute.
• December 2000 - Maui Civil Defense Agency received the draft of the Maui
County Multi-Hazard Mitigation Strategy from Pam Pogue.

Project Impact Community Partners
County of Maui Mayor’s Office
Maui Fire Department
Maui Police Department
Planning Department
Department of Public Works
Department of Water Supply
Maui Civil Defense Agency
State of Hawaii Civil Defense Agency
State of Hawaii Coastal Zone Management Program
State of Hawaii Hazard Mitigation Forum
Akaku – Maui Community Television, Inc.
Alexander and Baldwin Properties, Inc.
American Institute of Architects, Maui Chapter
American Red Cross
Blue Hawaiian Helicopters
Central Pacific Bank
Department of Education – Maui District
Hale Makua
Hana/East Maui Community Sustainable Committee
Kamehameha Schools
Lahaina Restoration Foundation
Lahaina Action Committee
Lowe’s Home Improvement Warehouse
Maui Chamber of Commerce
Maui Community College
Maui Contractors Association
Maui Economic Development Board
Maui Electric Company, Ltd.
Maui Hotel Association
Maui Memorial Medical Center
The Maui News
Maui Pacific Center
National Weather Service
Pacific Disaster Center
Pacific Radio Group
University of Hawaii, Social Research Institute
U.S. Small Business Association
Voluntary Organizations Active in Disasters (VOAD)
Walter Vorfeld & Associates

Chapter III Mission and Goals of the Maui County
Hazard Mitigation Strategy
Mission
The purpose of the Maui County Multi-Hazard Mitigation Strategy is to:
1. Provide a coordinated consistent set of goals for reducing or minimizing: human and
property losses; major economic disruption; degradation of ecosystems and
environmental critical habitats; destruction of cultural and historical resources from
natural disasters;
2. Provide a basis for intergovernmental coordination in natural hazard mitigation
programs at the state and county level;
3. Develop partnerships between the County and private sector, local communities and
non-profit organizations in order to coordinate and collaborate natural hazard
mitigation programs;
4. Identify and establish close coordination with county agencies responsible for
implementing the sound practices of hazard mitigation through building standards
and local land use development decisions and practices; and to
5. Provide for a continuing public education and awareness about the risks and losses
from natural disasters, in addition to natural hazard mitigation programs, policies and
projects.
Goals
The goals of the multi-hazard Maui Mitigation Strategy are to:
1. Protect public health, safety and welfare;
2. Reduce property damages caused by natural disasters;
3. Minimize social dislocation and distress;
4. Reduce economic losses and minimize disruption
to local businesses;
5. Protect the ongoing operations of critical facilities;

6. Reduce the dependence and need for disaster assistance funding after natural
disasters;
7. Expedite recovery disaster mitigation efforts during the recovery phase;
8. Promote non-structural flood and coastal erosion measures to reduce the risk of
damage to the surrounding properties and environmental habitats; and to
9. Establish a Maui County Hazard Mitigation Committee to support, implement and
revise the Maui multi-hazard mitigation strategy and to provide the support
necessary for an ongoing forum for the education and awareness of multi-hazard
mitigation issues, program, policies and projects.
10. Provide for adequate financial and staffing resources to implement the Maui Hazard
Mitigation Strategy.
Methodology
The geographic scope of the plan includes the Islands of Maui, Moloka’i and Lana’i.
The first step in completing a multi-hazard Mitigation Strategy is to undertake a risk and
vulnerability assessment (RVA). The RVA is a systematic way to categorize the effects
of hazards and provides a way to identify, compare, and prioritize risks. The RVA
establishes a factual basis and foundation to identify issues, and develop goals and
objectives for the mitigation plan. Also important, the data from the risk and vulnerability
assessment will establish a baseline in which to measure progress.
In order to begin to develop the risk and
vulnerability assessment, the hazards had to be
identified. For the purposes of this version of
the Multi-Hazard Mitigation Strategy, the
hazards were initially identified by a working
group1, then were presented to the Maui
County Emergency Managers, the Mayor and
his Cabinet and finally presented in a public
hearing on August 7th, 2000. (The public
hearing was taped and rebroadcast on by
Akaku).
Once the hazards were selected, data was then collected from Federal, state and
County agencies and the University of Hawaii. In order to profile each hazard, the data
needed had to include information on how to determine the extent and magnitude of
each hazard’s impact on the community. Data included damage reports, FEMA Flood
1 This working group included a representative from: Maui Civil Defense, Maui County GIS and Planning
Departments, Hawaii Coastal Zone Management, University of Hawaii Social Sciences Research Institute, the
Pacific Disaster Center and Maui Project Impact.
Meeting with the Mayor’s Cabinet to discuss
Hazard Mitigation Goals, June 2000

Insurance Rate Maps (FIRMS), impacts from past events, and best available
information on each hazard. More information on how each hazard has been profiled
and prioritized for this report is explained in subsequent sections of this Strategy.
Additional information was also obtained from numerous interviews with officials from
Federal, State and County agencies, academic institutions and public comment through
two scheduled public hearings.
After identifying the general areas at risk, data about population, property, economic
and environmental resources at risk was gathered in order to determine how and where
Maui County is vulnerable to the impact of various hazards. To more accurately
understand the community’s vulnerability it was also important to gather information on
the existing protection systems, both physical and regulatory currently in place within
Maui County.
Once the results from the risk and vulnerability assessment were known, a clearer
picture of the areas at risk, and an understanding of how and where Maui County is
vulnerable to the impacts of these hazards in terms of damage to public infrastructure,
critical facilities, environmental, societal and economic components was depicted using
Geographic Information System (GIS) maps. In some cases, the results were combined
with the Maui County tax assessors’ information (TMK data) such as plat, lot and
assessed structural values to give potential financial losses the community may face.
Based on the results of the RVA, the government capacity and available resources,
mitigation actions were identified in order to address the various hazards’ issues
potentially affecting Maui County. These options will allow Maui County to choose ways
in which to reduce the Counties vulnerability to natural hazard losses. In writing the
strategy, community plans were read, in addition to existing policies and on-going
programs. If Maui County focuses on strengthening existing plans, programs, policies
and procedures, and incorporates mitigation as part of the on-going process of County
management, it can avoid the duplication of efforts, thus saving time and money, and
achieve multiple objectives. The mitigation actions resulting from the Multi-Hazard
Mitigation Strategy should be incorporated into the Maui County Emergency Operations
Plan, the community comprehensive plans, and other pertinent planning and
implementation tools available such as local zoning, building and subdivision
ordinances.

Maui County Geography and Demographics
Maui Geography and Climate
The Island of Maui was formed by two volcanic cones, Haleakala in East Maui and the
Puu Kukui on West Maui. A relatively flat isthmus, formed of sand blown inland when
the sea was somewhat younger during the late Pleistocene period joins the two cones.
East Maui is geologically younger than
West Maui, as apparent by the
absence of deeply incised canyons and
extensive areas of volcanic lava and
cinders on the leeward slopes of
Haleakala. The lands more suitable for
agriculture, including the gentle slopes
of central Maui and tablelands of West
Maui, resulted from alluvial deposits
and the decomposition of basaltic
materials.
Rainfall varies considerable from one part of the Island to the other. The windward
areas of Maui get heavier rainfall than the leeward side. In East Maui, the highest
rainfall area is on the windward side of Haleakala between 2,000 and 4,000 foot
elevations, where the median annual rainfall is 200 to 300 inches. On the western side
of the island, median annual rainfall near the summit of Puu Kukui is approximately 350
inches. In contrast, leeward locations in central Maui such as Kihei have a mean annual
rainfall of 10 inches.
The Effects of the Island Topography on Climate
The topography of Maui plays a key role in defining the climatic zones on the island.
The volcanic slopes of Haleakala and Pu’u Kukui are very effective at forcing moist
trade wind air upwards to facilitate the
formation of clouds and showers. Hence,
windward areas of Maui are very wet,
averaging about 350 inches of rainfall per year
over Pu’u Kukui, and about 280 inches per
year over Haleakala. Conversely, subsiding air
over the leeward slopes of the island
suppresses cloud and shower development
leaving these areas dry. Along the leeward
coasts of both Haleakala and Pu’u Kukui, the
annual average rainfall is only about 10 inches.
The effects of Maui’s topography is clear when
the windward rainfall values are compared to the 28 inch estimate of average annual
rainfall over the open ocean near the Hawaiian Islands (Elliot and Reed 1984).
Maui Rainfall map provided by NOAA National
Weather Service

Trade winds are also deflected around the volcanic masses and funneled through gaps
and valleys, causing localized accelerations and leeward eddies. A notable example is
a feature known as the “Maui vortex”, which is a persistent circulation that exists during
trade wind conditions. The vortex usually occurs over the western slopes of Haleakala
and can result in the re-circulating of pollutants from sugar cane burning in Maui’s
Central Valley. In a recent case, strong open ocean trades of about 20 to 30 miles per
hour were further enhanced through deeply cut valleys in Pu’u Kukui. Gusts from this
event were estimated to be more than 70 miles per hour.
Moloka’i Geography and Climate
The island of Moloka’i was formed primarily by the joining of two separate shield
volcanoes approximately 1.8 million to 1.3 million years ago. Mauna Loa is to the west
and Kamakou is to the east with a plain in between. Lava from the younger East
Moloka’i Volcano flowed across the lowland of the Ho’olehua Saddle and terminated
against the flank and side scarps of the West Moloka’i Volcano. This is composed of
eroded sediment of the East and West Moloka’i Volcanoes. Near the end of the active
volcanism, the northern flank of the East Moloka’i Volcano slid into the ocean leaving
behind the towering pali (cliffs) on the northeast coast of the island
A third volcanic episode approximately 300,000 years ago was a comparatively small
one. It formed a 2500 acre peninsula in the sea below the steep cliffs of the north side
of Moloka’i Island proper. This is the Kalaupapa Peninsula, which is virtually isolated
from the rest of the island by cliffs 1600 to 2000 feet high. Erosion, deposition, slumping
and secondary volcanic events have modified the topography. The resulting shape of
the island is elongated in the east-west direction, much in the shape of a peanut. It is 38
miles long and 10 miles wide. It has an area of 260 square miles and a shoreline of a
little more than 100 miles.
East Moloka’i has a range of mountains whose highest peak, Kamakou, is 4,970 feet
high. Stream erosion has cut large amphitheater-headed valleys into its northern coast;
smaller and narrower valleys are found on its southern side, with an alluvial plain down
to the sea. In contrast, West Moloka’i has a sloping mountain, Maunaloa, which reaches
an altitude of 1,380 feet. It has rolling arid land rather than valleys and is considerably
drier than East Moloka’i. East Moloka’i supports the rain forest of Kamakou Preserve
(2,774 acres) near the summit while West Moloka’i supports plantations, ranches and
small farms. Pelekunu Preserve is located along Moloka’i’s extremely rugged north
coast, featuring the tallest sea cliffs in the world.
Bisecting the island, the broad Ho’olehua Saddle forms a low-lying coastal plain along
the south shore. The southeastern edge of the island is bordered by an alluvial plain
constructed from a series of semi-contiguous alluvia fans associated with upland
gulches. Three of the broader areas, formed at the base of the three major gulches of
Kaunakakai, Kawela, and Kamalo’o, have played important roles in early human
settlement of the southeast coastline. The deep loose soils, the presence of streams
and springs, the low, irregular shoreline, and the relative protection and resources of the

broad reef platform provided and inviting physical environment for early human
occupation in the southern coastal area.
Moloka’i has a warm year around temperature that fluctuates little between the seasons.
The average yearly temperature is 74 degrees F and ranges between 6 and 7 degrees
above and below. During the winter months (December through March) the nighttime
temperatures may drop to the lower 60’s with more rain and stronger water currents
coming to the island. The eastern portion of the island receives notably more rain than
the western portion, which lies in the rain shadow of the Kamakou highlands. The
average annual rainfall at the Moloka’i airport, which is located in the middle of the
island, is 20”. The annual mean precipitation is 20” in West Moloka’i and 35” in East
Moloka’i. The rainfall is highest on the west and windward slope of East Moloka’i,
decreasing rapidly toward the leeward coast. The kona storms are major storms that
come from the south and often drop huge volumes of rain. They occur once or twice a
year and may drop 8 to 10 inches of rain in a short time. These storms are island-wide
and normally occur between October and April. The trade-wind rains are more local in
character and occur through the year. They come in from the northeast and drop most
of their moisture in the northerly windward highlands, seldom on the southern or lee
side of the island. The greater part of the yearly rainfall in the highlands is from the
trade-wind rainstorms.
Population
In April 2000, Maui County has a population of 128,094 people. This includes Maui,
Moloka’i, and Lana’i. This is an increase in population of 42 percent over 1990 and an
81 percent increase since 1980 (Maui County Data Book 2000).


Area	1980		1990		2000			Percentage Change
	Population 	Population 	Population 	1980-1990  	1990-2000  	1980-2000
Maui Cty 70847		100374		128094		42%		 28%		 81%
Hana	  1423		  1895		  1855		33%		 10%	 	 30%
Makawao  19005		 29207		 36476		54%		 25%		 92%
Wailuku	 32111		 45685		 61346		42%		 34% 		 91%
Lahaina	 10284		 14574		 17967		42%		 23%		 75%
Molokai	  5905		  6587		  7257		12%		 10%		 23%
Lanai	  2119		  2426		  3193		14%		 32%		 51%

Combined number of residents and visitors determines Maui’s infrastructure and service
needs. The population of residents and visitors increased substantially between 1980
and 2000. The average daily visitor census for Maui County has remained fairly
constant from 1990 to 2000. The low was 37,060 (1991) while the high was 43,992
(1999).
Population projections developed by the Department of Economic Development and
Tourism estimates the 2020 population to be as follows: resident population 151,200;

average daily visitor population 76,000; the total population of 227,000. This would be
an increase of about 57,000 or 34 percent (Maui County Data Book 2000).

Land Use
Maui County is the second largest of the four Hawaiian counties. It
comprises a total of 1175 square miles of land. Maui has 728.6
square miles, Moloka’i has 260.9 square miles, Lana’i has 140.4
square miles, and Kaho’olawe has 45.0 square miles. The Island of
Maui has 149 miles of shoreline, Moloka’i has 106 miles, Lana’i has
52 miles, and Kaho’olawe has 36 miles (Maui County Data Book,
2002).
The State Land Use Commission has classified 25,516 acres in Maui County as urban,
310,396 as conservation, 406,792 as agricultural, and 8,196 as rural. The Federal
government owns 4.6 percent of all land, the state and counties own 33.6 percent, and
private ownership equals 61.8 percent (Maui County Data Book 2003).
Response Agencies
Maui County Civil Defense Agency is entrusted with the protection of life and property
within the County of Maui during emergency or disaster situations. The agency
operates under the authority of Chapters 127 and 128 of the Hawaii Revised Statutes,
as amended, and Section 8-15.1 of the Maui County Charter. The agency is responsible
for administering and operating the various Local, State and Federal Civil Defense
Programs for the County. This includes planning, preparing, and coordinating civil
defense operations in meeting disaster situations and coordinating post-disaster
recovery operations involving State and/or Federal assistance.
The Mayor of Maui County serves as a Deputy Director of Civil Defense, in addition to
his normal duties. A small four person staff that includes the Civil Defense
Administrator, Plans and Operations Specialist, a Civil Defense Staff Specialist, and a
Civil Defense Technician manages the day to day operations of the agency. During
disaster situations the Emergency Operating Center can be activated to include
Emergency Mangers from various governmental and private organizations. The Maui
County Civil Defense Agency also works at maintaining and upgrading the Civil Defense
Siren Warning System, trains governmental and civilian volunteer emergency response
force, and pursues a public awareness program on emergency preparedness.
Provided by Maui County GIS
 
MAUI COUNTY CIVIL DEFENSE AGENCY
EMERGENCY MANAGERS
• Mayor of the County of Maui
• Managing Director of the County of Maui
• Maui County Public Information Officer
• Maui County Police Department
• Maui County Fire Department
• Maui County Department of Parks and Recreation
• Maui County Department of Public Works and Waste Management
• Maui County Department of Water Supply
• Maui County Department of Housing and Human Concerns
• Maui County Department of the Corporation Counsel
• Maui County Planning Department
• Maui County Department of Finance
• State of Hawaii Department of Transportation/Harbors Division
• Radio Amateur Civil Emergency Service
• Amateur Radio Emergency Service
• Disaster Medical Assistance Team HI-1
• Verizon Hawaii
• Civil Air Patrol
• Maui Visitors Bureau
• American Medical Response
• Voluntary Organizations Active In Disaster
• State of Hawaii Department of
Transportation/Highways Division 
• State of Hawaii Department of Transportation/Airports Division
• State of Hawaii Department of Education
• State of Hawaii Department of Land and Natural Resources
• State of Hawaii Department of Human Services
• State of Hawaii Department of Defense/Hawaii National Guard
• National Weather Service
• American Red Cross
• Maui Economic Opportunity
• Maui Electric Company, Ltd.
• State of Hawaii Department of Health Maui County Project Impact
In support of the Disaster Resilient and Sustainable Community concept, FEMA has
developed an initiative called Project Impact. Project Impact encourages communities
to move from the current reliance on response
and recovery to an emphasis on mitigation,
preparedness and disaster management.
Under this initiative, communities are
demonstrating the economic benefits of predisaster
mitigation.
Maui County initiated their two-year Project
Impact community disaster mitigation program
in May 1999. The Project Impact Program
(1999-2001) is currently under the auspices of
the County of Maui Office of Economic
Development. FEMA provided the County
with a two-year grant of $300,000. Maui’s Project Impact efforts is focusing on the
following objectives:
Meeting of the Maui Project Impact Technical
Standards Subcommittee, August, 2000

Completing an island-wide survey to identify the current strengths and weaknesses of
Maui’s disaster mitigation efforts and guide future efforts;
Drafting and implementing isolated community preparedness plans for West
Maui/Lahaina and East Maui/Hana regions to reduce the negative impact resulting
from becoming isolated during and after
disasters; and Implementing an islandwide
public education and disaster
mitigation awareness campaign to educate
the public and encourage disaster
mitigation behavior.
To date, thirty-five businesses and
organizations have become Maui Project
Impact Partners, joining forces with other
county and state agencies to reduce
hazards on the Island of Maui.
Development of the Multi-Hazard
Mitigation Strategy will help Maui Project Impact meet its second objective and better
integrate its efforts with the County in order to accomplish the successful
implementation of this Strategy.
Project Impact Booth at Hana Fair, July, 2000

IV-1
Chapter IV Hazard Identification and Analysis
Hazards identification and analysis helps in making decisions about which hazards
merit special attention; what actions might be taken to reduce the impact of those
hazards and what resources are likely to be needed to successfully implement the
hazard mitigation measures.
Hydrologic, Wind, and Seismic Hazards
Hazards Identification
Identifying the hazards is the first step in any effort to reduce community vulnerability.
Identifying the risk and vulnerability for a community is the primary factor in
determining how to allocate finite resources to address what mitigation actions to take.
The hazard analysis involves identifying all of the hazards that potentially threaten
Maui County and then analyze them individually to determine the degree of threat that
is posed by each natural hazard. By addressing risk and vulnerability through hazard
mitigation, Maui County will only then reduce societal, economic and environmental
exposure to natural hazards impacts.
All hazards that may potentially occur in the community should be identified. This
includes both natural and secondary hazards – situations when one hazard triggers
others sequentially. For example, severe flooding that damaged buildings storing
hazardous water-reactive chemicals could result in critical contamination problems
that would dramatically escalate the type and magnitude of events. Dam failures may
occur as a result of an earthquake creating a dangerous flash flooding scenario for
communities on the other side of the dam. In areas of steeper, unstable slopes,
identifying the secondary effects of coastal storms and/or tsunamis may include flood
and debris damage resulting in rockslides or landslides. Additionally, coastal erosion
results from serious damage impacted on the coastline in the event of a tsunami,
hurricane and/or kona storm.
For the purposes of the Maui County Hazard Mitigation Strategy, the following hazards
will be addressed:
?? Hydrologic
?? Coastal erosion
?? Wind
?? Seismic
?? Tsunamis
?? Drought
?? Wildfire

IV-2
By collecting information for each potential hazard that may affect Maui County,
several determinations have been made:
(1) which hazards merit special attention;
(2) what actions might be taken to reduce the impact of those
hazards; and
(3) What resources are likely to be needed?
Historical data of past damages was also reviewed. This data provided information on
past damage costs, areas impacted, repetitive loss areas and those areas hardest hit.
HYDROLOGIC HAZARDS: INLAND AND COASTAL FLOODING
Floods
Hydrologic hazards include inland and coastal floods, storm surge, coastal erosion
and droughts. It is important to understand the interrelationship of hydrologic hazards
with other hazard groups. For example: extreme rainfall from a kona storm can cause
flooding, and sometimes flash flooding, and winds from a hurricane exacerbate storm
surge, high surf and coastal erosion.
Flooding is the accumulation of water within a water body and the overflow of excess
water onto adjacent floodplain lands. (FEMA, Multi Hazard Identification and Risk
Assessment, 1997) The floodplain is the land
adjoining the channel or river, stream, ocean or
other watercourse or water body that is
susceptible to flooding. Flooding is the result of
large-scale weather systems generating
prolonged rainfall or on-shore winds. Other
causes of flooding include locally intense
thunderstorms and dam failures. Floods are
capable of undermining buildings and bridges,
eroding shorelines and stream banks, tearing out
trees, washing out access routes, and causing
loss of life and injuries. Flash floods,
characterized by rapid onset and high velocity
waters, carry large amounts of debris.
Seasonal Pattern
The northwesterly trade winds directly influence the climate of the islands. Generally,
leeward locations are much drier and sunnier than the windward slopes. Conversely,
the windward side gets heavier rainfall than the leeward side. Rainfall varies
considerably, however, from one part of the island to the other. On Haleakala, the
2.000 to 4,000 foot elevations receive 200 to 300 inches of rainfall each year. (FEMA

IV-3
Flood Insurance Study or FEMA FIS, August 3, 1998). On the western side of Maui,
the average rainfall near the summit of Puu Kukui is 350 inches. In sharp contrast,
leeward locations in south Maui receive an average of 10 inches. (FEMA FIS, 1998).
The climatic pattern is much the same on Moloka’i and Lana’i. It also has two seasons
of winter and summer but with a slight variation in the months. The wetter season
extends from December through March while the dry summer season is June through
August. The average rainfall for Moloka’i is somewhat less than Maui. The eastern
slopes of Kamakou receive an average of 150 plus inches a year, tapering off to 10-12
inches per year in places in the western part of Moloka’i. This disparity in annual
rainfall on the two islands arises from the fact that the Hawaiian Islands extend over a
latitudinal belt that is a zone of desiccation throughout the world except where marine
air masses are forced to rise over mountain barriers. Orographic rainfall results in the
cooling of the uplifted air masses, creating extremely high rainfall under the ideal
conditions of mountain elevation and trend, and wind direction and velocity.
Damage
Water related damage caused by inland and coastal flooding in the United States
account for over 75 percent of federal disaster declarations (FEMA Multi Hazard
Identification and Risk Assessment, 1997). Floods occur in all 50 states and US
Territories. FEMA estimates that over 9 million households and $390 billion in property
are at risk from flooding. In Hawaii, floods caused by rainstorms, tsunamis, and
hurricanes claimed more than 350 lives and caused more than $475 million in
damages before 1983. From January 1983 – July 1992, twelve lives were lost due to
various floods in Hawaii.
Flood damage can result from the effects of short and long-term increases in water
levels through precipitation, wave action, high-velocity flows, erosion and debris.
Coastal flooding can originate from a number of sources. Coastal storms such as
hurricanes and kona storms, and ocean disturbances such as seismic activity and
sub-ocean landslides which can cause tsunamis, generate the most significant coastal
flood damage. Coastal storms and hurricanes create coastal flooding along the open
ocean coastline. Whether situated on a coastal
headland, barrier beach, or bluff sitting high atop
the coast, the ocean-land interface is a place of
great danger and sudden transformation during
storms. (The Hidden Costs of Coastal Hazards,
2000)
Under the National Flood Insurance Program
(NFIP), FEMA is required to develop flood risk
data for use in both insurance rating and
floodplain management. FEMA develops these
data through Flood Insurance Studies (FIS). In FISs, both detailed and approximate
analyses are employed. Generally detailed analyses are used to generate flood risk

IV-4
data only for developed or developing areas of communities. For undeveloped areas
where little or no development is expected to occur, FEMA uses approximate analyses
to generate flood risk data.
Using the results of the FIS, FEMA prepares a Flood Insurance Rate Map (FIRM) that
depicts the Special Flood Hazard Areas (SFHAs) within the studied community.
SFHAs are areas subject to inundation by a flood having a one percent chance or
greater occurring in any given year. This flood, which is referred to as the 100-year
flood (or base flood), is the national standard on which the floodplain management
and insurance requirements of the NFIP are based. The FIRM shows Base Flood
Elevations (BFEs) and flood insurance risk zones. The FIRM also shows areas
designated as a regulatory floodway. The regulatory floodway is the channel of a
stream plus any adjacent floodplain areas that must be kept free of encroachment so
that the 100-year flood discharge can be conveyed without increasing the BFE more
than the specified amount. Within the Special Flood Hazard Area (SFHAs) identified
by approximate analyses, the FIRM shows only the flood insurance zone designation.
The FEMA FIRM designations are defined below.
FEMA Flood Insurance Rate Map Definitions
VE Zones
Zone VE is the flood insurance rate zone that corresponds to the 100-year coastal floodplains that have additional
hazards associated with storm waves. Whole-foot base flood elevations derived from the detailed hydraulic
analyses are shown at selected intervals within this zone.
Zone A
Zone A is the flood insurance rate zone that corresponds to the 100-year floodplains that are determined in the FIS
by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no base flood
elevations or depths are shown within this zone.
Zone AE
Zone AE is the flood insurance rate zone that corresponds to the 100-year floodplains that are determined in the
FIS by detailed methods. In most instances, whole foot base flood elevations derived from the detailed hydraulic
analyses are shown at selected intervals within this zone.
Zone AH
Zone AO is the flood insurance rate zones that correspond to the areas of 100-year shallow flooding (usually areas
of ponding) where depths average are between 1 and 3 feet. Whole-foot base flood elevations derived from the
detailed hydraulic analyses are shown at selected intervals within this zone.
Zone AO
Zone AO is the flood insurance rate zone that corresponds to the areas of 100-year shallow flooding (usually sheet
flow on sloping terrain) where average depths are between 1 and 3 feet. Average whole-depths derived from the
detailed hydraulic analyses are shown within this zone
500-Year Flood Zone (or Zone X)
Zone X is the flood insurance rate zone that corresponds to areas outside the 500-year floodplain, areas within the
500-year floodplain, and to areas of 100-year flooding where average depths are less than 1 foot, areas of flooding
where the contributing drainage area is less than 1 square mile, and areas protected from the 100-year flood by
levees. No base flood elevations or depths are shown within this zone.

IV-5
Types of Flooding Events, Frequency, Magnitude and Location
Coastal Storms
Major flooding events in Hawaii are caused by storms, storm surge, high surf and
tsunamis (tsunamis will be covered in Seismic Hazards section). The climate of Hawaii
is characterized by a two-season year; cool and warm. Floods occur during both
seasons. Major floods typically occur during the rainy winter (October through April)
and account for 84 percent of the floods in the islands. (State of Hawaii Flood Hazard
Mitigation Plan, December 1996) Four types of storms produce heavy precipitation in
Hawaii:
Kona storms. These wintertime storms, from November to April, are in the wettest
period of the year and locally called the Hoo’ilo season. The trade winds from the
northwest slacken during this time, allowing storms from the south to more easily
approach the islands. Hence the name kona which means leeward direction indicates
the direction from which these storms come. The kona winds are generally warmer
carrying moisture, which is dropped as rain over the entire island, more or less evenly.
The lower elevations and southern, drier side of the islands get most of their rainfall at
this time. It is about 25-30 inches each season. Because of the potential combination
of high winds and heavy rains, these events could cause coastal erosion, and inland
and coastal flooding over larger geographic areas of Maui and Moloka’i, thereby
creating a greater impact on the islands.
Frontal Storms. Frontal storms usually occur during the period from December through
March. They originate over the Pacific Ocean as a result of the intersection between
polar and tropical Pacific air masses and move eastward over the Islands. Rainfall
from these storms is enhanced by mountainous areas (such as Haleakala and the
West Maui mountains on Maui and Kamakou on Moloka’i) and can be accompanied
by widespread precipitation. The effects of frontal storms are often greater within the
mountainous regions of Maui and Moloka’i. Heavy rainfall, continuous over a period of
several hours, quickly creates disaster conditions in high sloping areas such as these,
prone to landslides and flash flood conditions in lowlands with poor drainage.
Upper level lows. Upper level lows and troughs can occur any time of the year. In
many instances, upper level lows have little or no effect on the lower levels of the
atmosphere. However, these lows are sometimes able to tap into the marine layer
and induce heavy showers that sometimes produce flash flooding.
Tropical Cyclones. Hurricanes or tropical storms hitting or passing by the Hawaiian
Islands cause heavy rains, storm surge, high winds and surf. Impacts from these
events have included coastal erosion, severe inland and coastal flooding. Extensive
wind damage can occur from the stronger tropical cyclones (hurricanes and tropical
storms).

IV-6
History of flooding on Maui
Island-wide stream flooding because of heavy rains
DATE DESCRIPTION
November 19. 1900 Flash flood
December 23, 1906 Flash flood
January 14, 1916 Flash flood
April 18, 1918 Flash flood
August 10, 1930 Flash flood
November 18, 1930 Flash flood
January 2, 1946 Flood
December 20, 1946 Flash flood
April 2, 1948 Flash flood
November 30, 1950 Flash flood
February 22, 1951 Flash flood
May 12-13, 1960 Flood
October 24, 1961 Flash flood
March 13, 1963 Flooding
January 23, 1965 Flash flood
March 13-16,1968 Flooding
November 28, 1968 Minor flooding
January 28, 1971 Flooding
April 19, 1974 Flash flood
January 6-14, 1980 Flooding
August 3-4, 1981 Flooding
October 27-28, 1981 Flooding
March 30-31, 1982 Flooding
April 1-3, 1982 Flooding
July 16-17, 1982 Flooding
December 23-24, 1982 3-5" of rain
May 23, 1984 Minor flash floods
December 24-25, 1984 Flash flood
October 17-18, 1985 Flash flood
November 18, 1985 Minor flash floods
February 15, 1986 Flash flood
November 10-11, 1986 Minor flash floods
April 21-22, 1987 Minor flash floods
April 26, 1987 Flash flood
May 5-6, 1987 10" of rain, flash flooding
January 28-29, 1988 Flash flood
November 4-5, 1988 Extensive flooding

IV-7
December 5-6, 1988 Flash flood
February 10-11, 1989 Minor flash floods
March 1-4, 1989 Minor flash floods
January 14-22, 1990 Up to 20" of rain, flooding
January 27, 1991 Flooding
March 19-21, 1991 Flooding
July 21-23, 1993 Flooding, remnants of H. Dora
West Maui stream flooding because of heavy rains
DATE DESCRIPTION
January 26, 1916 Lahaina & Olowalu flooded
November 30, 1950 Flash flooding at Lahaina
May 12-13, 1960 Kahoma Stream
October 31, 1961 West Maui, Kahoma Stream
March 17-18,1967 7" in 5.5 hrs at West Maui
January 28, 1971 Lahaina, Kauaula Stream (Hale, Cannery, Kelawe
Camp)
February 24, 1972 5-8" in 5 hrs at West Maui, Lahaina
November 24, 1974 Ka'anapali, Honokawai
May 5-6, 1987 10" of rain, flash flooding in Lahaina
December 5-6, 1988 Over 10" of rain
January 19-20, 1997 Flooding Lahaina
Northwest Maui stream flooding because of heavy rains
DATE DESCRIPTION
November 2, 1961 Flash flooding at Napili, Honolua
December 19, 1964 Flooding
March 17, 1967 Napili Bay
March 24, 1967 Heavy rains at Napili Bay
March 13-16, 1968 24" in 48 hrs at Napili Beach, Honolua Pa'akea
North central Maui stream flooding because of heavy rains
DATE DESCRIPTION
November 14. 1900 Kahului
February 13, 1903 Flash flood at Wailuku
January 14, 1916 17,000 cfs at Iao Valley
December 24, 1920 Storm, flooding at Wailuku
November 18, 1930 Flash flood Iao Stream
January 2, 1946 Flooding of Iao Stream
November 30, 1950 Flash flooding at Iao Valley, Wailuku
December 3, 1950 7550cfs, 5" rain in 2 hrs at Iao Stream
November 2, 1961 5700 cfs at Iao Stream
February 4, 1965 Sheet flow

IV-8
January 27-28, 1971 5820 cfs at Iao Stream, 2 ft at Pai'a
February 8, 1972 3.5" in 1 hr at Wailuku
November 12, 1978 Flash flooding at Iao Valley, Kahului
March 30-31, 1982 Flooding at Iao Valley
May 5-6, 1987 10" of rain, flash flooding at Wailuku, Kahului
February 3-5, 1989 Flash flooding near Haiku
April 12-13, 1994 Flash flood, mud slides
Windward Haleakal'a stream flooding because of heavy rains
DATE DESCRIPTION
April 25-28, 1965 Flash flood at Hana
April 15-16, 1968 East Maui esp. Honomaele Stream
October 27-28, 1981 Flooding - road to Hana
March 30-31, 1982 Flooding - road to Hana
July 21-22,1982 Flash flooding
August 1, 1982 Flash flooding, esp. Ka'anapali
May 23, 1984 Minor flash floods – road to Hana
February 15, 1987 10" rain
March 24, 1988 Flooding - road to Hana
March 19-21, 1991 Flooding - road to Hana
November 26-27, 1992 Severe flooding
October 23, 1993 Flash flood, mudslide
April 12-13, 1994 Flash flood, mudslide
Southwest Maui stream flooding because of heavy rains
DATE DESCRIPTION
January 26, 1916 Flood – Kihei
January 29, 1930 Flash flooding at Kulat, Kihei
February 22, 1951 Flood – Kihei
December 21, 1955 Flood – Kihei
March 24, 1967 6" in 6 hrs at Kihei
January 28, 1968 Flood – Kihei
January 27-28, 1981 Flooding - 6ft at Kihei
December 5-6, 1988 Over 10" of rain at Kihei
Inland Flooding
Stream Flooding
Stream flooding is a very common occurrence on both Maui as can be expected from
the deep V-shaped valleys of west Maui, carved as the result of one million years
worth of stream flow. Along the eastern half of Maui, the mountains and valleys are
much younger and as a result, the valleys and streams are not as well developed.

IV-9
Most of the streams cut steeply down to the narrow coast of Hana, often in cascading
waterfalls, a hallmark of this region. According to the National Oceanic and
Atmospheric Administration (NOAA) National Weather Service (NWS), the greatest
amount of rainfall occurs in West Maui (300 inches)
at the summit, and nearly as high in east Maui (280
inches). (Fletcher 2000). Rainfall decreases
dramatically toward southern Maui and west of West
Maui and is the lowest (<15 inches) in the area of
Lahaina and Kihei.
Damage
The north and central areas of Maui and the Hana
Coast have the greatest stream flooding histories.
Kahului, Maui’s most urbanized area and location of
the Island’s major airport, commercial port and most
of the retail and wholesale facilities, is a frequent victim of serious inland flooding
events. (Pers. Comm. Roger Kawasaki, NOAA National Weather Service) Stream
flooding is a particularly significant hazard in the areas where there are streams in
close proximity to residential development such as in the south Maui area: Kalama
Park, Kamole Beaches and Lipoa Avenue. The three principal streams in the area
that flow westward and seaward only during periods of excessive rainfall are
Kulanikakoi, Waipuilani, and Keokea Streams. They are narrow and poorly defined
waterways. Localized depressions, ponds, swales and ditches are typical of areas
along Kihei Road. Only seven gulches have well defined watercourses, and even
these do not maintain stabilized channels completely across the lowland area to the
ocean.
Stream flooding in the Kaupo region, which has half the rain fall as Hana, is a high
risk. Here there are many stream mouths that flood during intense rain events. On the
back coastal road from Kipahulu to Kaupo, there are many areas where the road
suddenly dips down and becomes flooded from low water crossings. During the storm
of 1968 this area experienced extensive damage as six miles of unpaved road was
closed to traffic for several days, a result of four timber bridges and three culverts
being destroyed). Areas particularly susceptible to flooding are Nuu, Huakini and
Waiu Bay, Pakowai and Waiopai.
Stream flooding on Moloka’i
Because of the lack of rainfall over most areas of the island, the only perennial
streams which reach the sea are those of the large valleys on the windward side of
East Moloka’i. The permanence of the streams on the northern slope are the result of
numerous high level springs which issue from the dike complex where exposed by
erosion. Other streams are fed from the seepage of swamps. Due to the geological
conditions such as the steepness of the terrain and the intermittent character of the
heavy rainfall, the streams in most of the area have high flows and velocities during

IV-10
heavy rainfall. The streams on the southern slope of the East Moloka’i and most areas
of West Moloka’i are perennial in the upper courses but these streams normally lose
their water to seepage and evaporation long before reaching the coast. The
expectation is after heavy rainfalls or Kona storms when flows in these streams reach
the ocean.
Damage
The major flood problems are associated with the heavy flow of four water courses in
East Moloka’i, the Wailua Stream, Wawaia Gulch, Kamalo Gulch, and Kawela Gulch.
The primary causes of flood damages are overflow of the water courses, inadequate
highway bridge openings and periodical accumulation of deposits on the stream beds
which result in the reduction of flow capacity. Minor flooding problems are caused by
overland sheet flow. Along the eastern limits of Wailua Valley, flooding due to water
flowing rapidly down the steep hillside onto level areas causes ponding to occur.
Sheet flow occurs at east Kawela and west Wawaia valleys when water rushes over
cleared portions of the flood plain after intense rainfall. Due to the lack of drainage
ditches and channels, the water runs as “sheet” flow towards the ocean.
Flash Floods
Flash floods are characterized by a rapid rise in water level, high velocity, and large
amounts of debris. Flash floods are capable of tearing out trees, undermining
buildings and bridges, and scouring new
channels. Flash floods are more prevalent in
areas where there is a predominance of clay
soils that do not have high enough infiltration
capacities to absorb water fast enough from
heavy precipitation events.
Flash floods may also result from dam failure,
causing the sudden release of a large volume
of water in a short period of time. In urban
areas, flash flooding is an increasingly serious
problem due to the removal of vegetation, and
replacement of ground cover with impermeable surfaces such as roads, driveways
and parking lots. In these areas, and drainage systems, flash flooding is particularly
serious because the runoff is dramatically increased.
The greatest risk involved in flash floods is that there is little to no warning to people
who may be located in the path high velocity waters, debris and/or mudflow. The
major factors in predicting potential damage are the intensity and duration of rainfall
and the steepness of watershed and stream gradients. Additionally, the amount of
watershed vegetation, the natural and artificial flood storage areas, and the
configuration of the streambed and floodplain are also important.

IV-11
Precipitation, which sometimes equals the average annual rainfall, has occurred
throughout the historical record. Flooding in areas around Kihei and Lahaina on Maui
is partially due to the fact that the topography is characterized by an abrupt transition
in slope at the coastline. Many historic floods in these two areas occurred after heavy
precipitation in higher elevations, which fed to narrow stream channels and drainage
channels near an arid coast to the point of overflow. (Fletcher May 2000, p.2). Flash
flooding is a common occurrence in the Lahaina area. This is caused by a couple of
things; the steep slope of the foothills on the westside of the West Maui Mountains,
and the lack of vegetation because sugar cane is no longer planted in this area.
Damage
According to the May 2002
version of the Atlas of the
Natural Hazards in the Hawaiian
Coastal Zones, a number of
flash flood events resulting in
significant damage have
occurred since 1900. Since
1879, 19 damaging floods have
occurred in Lahaina. (Fletcher
2000) Wailuku, Maui’s county
seat, also experiences serious
sheet flow and flash flooding
events. Historically, flash
flooding has been a serious
problem in the Kahului and
Wailuku areas, due to large amounts of water discharge from the steep hillsides of
the Iao Valley cumulatively collecting when encountering a coastal lowland area.
Flash flooding also poses serious threats in this low-lying coastal terraced near
Waihee Point and Waihee Beach Park. The Waihee stream area is popular with
visitors for hiking. However, the high potential, and past flash flooding events poses
serious concerns in this area, as visitors are unaware of these risks. An additional
concern is debris flow. High velocity flows from the streams within the Iao Valley
area, bring rocks and boulders to the beaches near Waihee. (See May 2002 Atlas of
the Natural Hazards in the Hawaiian Coastal Zones for complete historical listing of
these events)
Sheet flow
Sheet flow is more prevalent in those areas characterized by steep grades and
sudden high precipitation events. In west Maui, sheet flow flooding tends to be a
problem. This area of Maui encompasses two major watersheds – Lahaina
Watershed and Honoloa Watershed. The Honoloa Watershed spans the area north of
the Ka’anapali Resort to Honoloa Bay, approximately 24,800 acres in size. The
highest point of the watershed is the Puu Kukui peak in the West Maui Mountains
Provided by Dr Charles Fletcher UH

IV-12
(Mauna Kahalawai). Deep valleys and narrow winding channels draining to the ocean
incise the watershed. Grades begin at
about 16% and flatten to 6% towards the
ocean. Defined channels exist in the
major valleys, varying from 5 to 10 feet
deep and 10 to 20 feet wide. The
Lahaina watershed is approximately
4,920 acres encompassing Lahaina Town
and Pomona subdivision. (Maui
Community Plan Infrastructure
Assessment 1992) The remaining upper
area of the watershed is mountainous
with deeply incised canyons and is part of
the West Maui Forest Reserve.
On Moloka’i, sheet flooding occurs along the eastern limits of Wailua Valley. This is
caused by water flowing rapidly down the steep hillside onto level areas causing the
water to collect in ponds. Sheet flow also occurs at east Kawela and west Wawaia
valleys when water rushes over cleared portions of the flood plain after intense
rainfall.
Damage
Heavy precipitation from past storm events on Maui (such as April 15-16, 1968),
creates serious storm water runoff problems from the high velocities of water flowing
down the pasturelands. In downtown Hana, this high velocity sheet flow has caused
road damage. (Kevin Kodama, NOAA National Weather Service) During the Storm of
1968, drainage ditches in Hana town including its bedding, and sections of the earth
banks were washed downstream into the ocean. (Corps of Engineers, 1968)
Additionally, road shoulders, retaining walls and pavement were also severely
damaged. Holoinawawae Stream was also damaged. (Corps, 1968)
Storm water runoff
Drainage refers to the system or area where rainfall and storm water runoff travels to
waterways or bodies of water. Drainage presents itself as a problem in the form of
flooding due to the development or alteration of natural areas and drainage patterns.
Geology and rainfall are the major influences on drainage systems. Runoff is a
function of infiltration capacity (soil type), relief, vegetal cover, and type and extent of
development (amount of impermeable surface).
Sediment erosion is a naturally occurring process that is accelerated by human
activities (West Maui Watershed Owners Manual, November 1997) There are
watersheds on Maui that are high producers of sediment as a result of Maui’s erodible
soil, steep slopes and periodic rainfall, particularly at high elevations. Heavy

IV-13
Abandoned sugarcane fields, Lahaina
precipitation events cause soil and sediment
erosion and storm water runoff conditions that
significantly alters river channels carrying large
amounts of sediment downstream, plugging
drainage systems and causing flooding and
damage to homes and roads. Soil erosion also
becomes a serious problem for public
infrastructure when high velocity streams
cause scouring to occur at the base of bridge
supports. Flooding and high wave conditions
erode coastal lands supporting roads.
Rapidly developing downstream communities are
often overwhelmed by the large amounts and high peaks of storm water and sediment
flowing from upstream areas down normally dry or minimally flowing streams and
irrigation channels (Lahainaluna area). Environmental degradation can occur when
debris flows and storm water runoff occurs. Once flooding occurs, sediment particles
are quickly transported downstream to the ocean where the suspended sediments and
debris creates turbid conditions that are harmful to coral reefs when particles abrade
and smother coral reefs. This is particularly true on Moloka’i. Because of the limited
development in the coastal zone on Moloka’i, the hazards caused by storm water
runoff affects the natural environment more so than coastal development. Some of the
most expansive reefs in the state occur along the southern coast of Moloka’i. On rainy
days plums of red-brown sediment can be seen lining the entire south shore. Where
the shoreline progrades seaward, the reef flat becomes buried in mud. Storm water
runoff and debris flows carry trash, motor oils, landscape chemicals, pet ands
livestock feces and other pollutants to streams and into the ocean.
In terms of urban land use, construction sites and roadsides expose large areas of
bare soils that are highly susceptible to runoff and erosion. Construction sites can
contribute significantly to storm water runoff and sediment erosion because Maui’s
soils are so fine and the close proximity of new development to the shoreline.
Construction and development within the watershed contributes sediments and
pollutants to storm water runoff during the grading and construction phase. After
construction is completed, the paved or impermeable surfaces create increased
volume and peak rates of storm water runoff flow. Because, major sediment retention
basins are mauka of urban areas, urban runoff is transported directly to the ocean
through streams, gulches and some storm drains.
Studies conducted by researchers in conjunction with the West Maui Watershed
project showed that pineapple and sugar cane fields generate higher loads of runoff
(West Maui Watershed Owners Manual, December 1997). Pineapple fields generate
the most runoff immediately before planting and for the first 8 – 12 months after
planting, before the plant canopy cover is complete. (Marty Stevenson, 1997)
Sugarcane fields were found to be highly vulnerable to erosion and runoff for a period

IV-14
of roughly 4 – 6 months after being planted (Stevenson, 1997) Cane roads are also
susceptible to erosion. On Moloka’i, much of the red-brown mud or silt comes from
excessive soil erosion in watersheds that have been denuded by deforestation and
feral ungulates.
Damage
Historically, the Iao Stream has caused the major flood problem in the Wailuku-
Kahului area. Due to the steep ground gradient, flooding from high velocity and large
flow quantities has caused considerable property damage and loss of life. Another
flood problem in the Wailuku area has been the overtopping of the irrigation ditches.
During periods of heavy rainfall, the irrigation ditches are incapable of carrying the
irrigation water and storm water runoff that is intercepted by the ditches. Flooding in
Wells Park area and along Main Street has occurred during periods of heavy rainfall.
Secondary areas of flooding occur in the low-lying sections of Kahului. The flooding
primarily consists of the inundation of the streets and low-lying residential areas. The
lack of adequate storm drainage facilities and the inability of local dry wells to
accommodate the overtopping gulches and ditches cause such flooding.
Records for flooding on Moloka’i are not as good as on Maui but the observational
data shows flooding does occur in both the arid and wetter regions of Moloka’i. There
are only a few places where flooding has much of an impact on the developed areas
of the coastal zone. The primary causes of flood damages are overflow of the
watercourse, inadequate highway openings and periodical accumulation of deposits
on the streambeds, which result in the reduction of flow capacity.
At least two coral species that are rare throughout the Hawaiian Archipelago can be
found in the shallow water at Palaau on Moloka’i. A third rare coral species is found at
Pukoo. Impact of land-derived sedimentation on the coral reefs of south Moloka’i has
been and continues to be a major environmental concern. Unchecked, this can be a
causative factor in the destruction and death of the coral.
Ponding
Storm water runoff and debris
flows also negatively impact
public infrastructure such as
roads and bridges as water
collects. This is typically the
result of inadequate drainage
systems in the immediate area,
creating ponding conditions
oftentimes making roads
impassible. Standing surface
water develops after intense Suda Store, Kihei, October, 1999

IV-15
rainfall events where poor soil permeability and urbanization prevent adequate water
drainage. This may interrupt road transportation and damage low elevation buildings.
Road closures can be a critical issue in Maui when these events have the potential to
isolate communities.
Damage
The direct cause of flooding in Kihei is the inadequate capacity of existing channels.
Between Kihei Road and Pi’ilani Highway, there are four gulches (Waiakoa,
Kulanihakoi, Waipuilani and Keokea) that flow in an east-west direction and drain
approximately 65% of the watershed. Storm runoff flows at high velocities above the
coastal plain because of the steep ground gradient at upper elevations. Gradual
slopes in this area approximate 4-5 percent with elevations ranging from 5 to 90 feet.
These slopes establish little or no well-defined surface drainage pattern. The drainage
ways do not maintain stabilized channels and are generally narrow and poorly defined
because of intermittent rainfall and minimal runoff throughout most of the year. As the
floodwaters approach the coastline, ponding occurs because of inadequate outlets to
the sea, which is frequently plugged with ocean-deposited sand. The high volumes
and velocities of the flood waters of these streams, on their approach to the Kihei flood
plain, cause overtopping of existing drainage structures crossing Kihei Road. (Maui
Community Plan Update Infrastructures Assessment, 1992) This flat low-lying coastal
area is the recipient of all of this surface runoff and contributes to the flood problems in
the Kihei area.
In Kihei, the transportation and even evacuation problems are particularly severe due
to the North/South Kihei Road that runs parallel, and perilously close, to the coastline.
This road has been flooded on many occasions by low magnitude coastal flood
inducing events such as south swells, Kona storms and heavy rains.
Rain Gages/Flood Forecasting Systems
Hydronet
The Hydronet system is a statewide network of NWS maintained and operated tipping
bucket rain gages whose primary purpose is to support the flash flood forecast and
warning operations of the Honolulu Forecast Office. Network communications are
handled via commercial telephone lines or cellular phones that contact data loggers
attached to each rain gage. Each data logger records rainfall to a resolution of 0.01
inches every 15 minutes and contains enough memory to hold several days of data.
The Hydronet computers are programmed to automatically interrogate each gage
every three hours during benign weather conditions. This frequency can be increased
to automatically interrogate every hour when heavy rain is anticipated or is already
occurring. Each gage is also programmed to call the Hydronet computers when
rainfall intensities reach or exceed one of four pre-selected thresholds. These

IV-16
threshold values are currently set for 0.25, 0.50, 0.75, and 1.00 inches per 15 minute
period, or 1.00, 2.00, 3.00, and 4.00 inches per hour, respectively. After receipt of a
heavy rain data message from the gage, the Hydronet workstation notifies the
forecasters of the event via printed message, on-screen computer terminal message,
and audible and visual signals in the office. Alarm messages are also sent to
participating county warning points for intensities of 2.00 inches per hour or greater.
All Hydronet gages are visited routinely for maintenance and calibration purposes.
The Hydronet alarm system at the Maui County Warning Point is tested quarterly to
ensure receipt of messages.
Areal Mean Basin Estimated Rainfall (AMBER)
AMBER is a product derived from WSR-88D weather radar data that is used for flash
flood forecasting and detection purposes. The AMBER system utilizes the maximum
spatial and temporal resolution radar data available to produce specific basin
averaged rainfall estimates. Output includes hourly basin accumulation rates as well
as basin accumulation totals over user-specified periods. Basins have been
delineated using 30-meter digital elevation model data processed through a software
extension from a Geographic Information System (GIS).
For the State of Hawai’i, AMBER output is currently available from the WSR-88D radar
on Moloka’i with basins delineated over the island of O’ahu and the islands in Maui
County. Flash Flood Guidance (FFG) values are also tied to AMBER data to assist
forecasters in the warning and advisory decision making process. FFG values
indicate the amount of basin averaged rainfall needed to produce small stream
flooding over different time periods.
Coastal Flooding
Storm Surge
One of the most dangerous aspects of a hurricane is a general rise in sea level called
storm surge. It begins over the deep ocean; low pressure and strong winds around
the hurricane’s center (“eye”) raise the ocean surface a foot or two higher than the
surrounding ocean surface forming a dome of water as much as 50 miles across.
(National Science Foundation, 1980) As the storm moves into shallow coastal waters,
decreasing water depth transforms the dome of water into a storm surge that can rise
20 feet or more above normal sea level and cause massive flooding and destruction
along the shoreline in its path. This problem is even more critical in the event when
there is additional impact caused by high, battering waves that occur on top of the
surge.
Storm surge floods and erodes coastal areas, salinizes land and groundwater,
contaminates the water supply, causes agricultural losses, results in loss of life, and
damages structures and public infrastructure. Maui has 149 miles of coastal

IV-17
shoreline. Moloka’i has 106 miles. (Maui
County Data Book, 2002). Flooding from
storm surge in the immediate coastal areas
occurs primarily as a result of tropical storms,
hurricanes and seasonal high waves. During
these events, high winds and surf can push
water several feet and even hundreds of
yards inland Conditions can be exacerbated
by large waves that form on top of rising
water. The degree of damage caused by
storm surge depends on the tidal cycle
occurring at the time of the event. During high
tides, water levels can be significantly higher than low tide recede further inland and
cause more extensive damage. The area of impact of storm surge flooding is
confined to regions along the immediate coastline and typically extends to a few
hundred feet inland.
Those areas most susceptible to storm surge are coastlines that are uniformly flat or
only a few feet above mean sea level, the storm surge will spread water rapidly inland.
Typically, storm surge diminishes one to two feet for every mile it moves inland. For
example, a 20 foot surge in a relatively flat coastal area, where the land may only be 4
to 6 feet above mean sea level, would be felt 7 to 10 miles or more inland.
Damage
On Maui, the areas of Waiehu and Waihee,
located in coastal embayment, the risk of
coastal flooding is particularly higher due to
the exposure to annual wave heights
measuring as much as 20 feet during the
winter, in addition to hurricanes approaching
from an easterly direction. (Fletcher, May
2000). Ponding from heavy precipitation
and poor storm water designs in Kahului
and Wailuku is a common problem. (Pers.
Comm., Cerizo, Kawasaki) Landslide,
debris flow and storm water runoff may also
impact the Wailuku Heights area. Built
within the high slopes and valley regions of the backside of Iao Valley, this densely
developed residential area is at risk to flooding sheeting down from the steep slopes.
The Kihei watershed is on the western slope of Mount Haleakala on a curved band
that extends approximately 8 miles south from Mokulele Junction to Wailea and
approximately 15 miles east fro the shore to the summit of Haleakala. The coastal
area is relatively flat and characterized by sandy beaches of varying widths. Thirty-two
gulches, ravines, and gullies drain the mountain slopes above the Kihei coastal

IV-18
lowland. Where there are small beaches that coincide with stream mouths near
Wailea, and in the south at Poolenalena the threat from stream flooding is high. The
coast of Kihei and Maalaea is heavily developed. Therefore, because of the close
proximity of coastal development to the ocean, coastal flooding from storm surge is a
potential threat in the areas of Maalaea, Kihei, and Makena. Kealia Pond and
surrounding coastal lowlands can also be inundated by storm waves and stream
flooding.
Between Laniupoko Point and Ukumehame Park, the coast is relatively undeveloped
except for the small recreational area at Olowalu Point. A low-lying coastal terrace that
parallels the long and narrow sandy beach characterizes this area. Numerous larger
stream channels cut through this region draining the wetter West Maui Mountains.
While the streambeds are generally dry year round, they are known to quickly flood
during extreme rainfall events in the immediate area and in the West Maui Mountains,
just inland of the coastal zone. (Pers. Comm. Roger Kawasaki, NOAA National
Weather Service) The only road connecting West Maui to the rest of the Island
frequently bears the brunt of flooding events as the road gets closed from flooding as
well as mud and landslides resulting from heavy rains in this mountainous area.
Olowalu, including Ukumehame Park and Valley area is particularly susceptible to
coastal flooding from more frequent events caused by south swells. In the events
where there have been significant amounts of precipitation, up to Launiupoko Point
and Ukumehame Park area is vulnerable to rock slides from rock outcrops hugging
the only coastal road from South Maui to West Maui.
In areas characterized by low coastal slopes at the bays and stream mouths, the risks
from coastal and stream flooding is greatest in the Keanae and Nahiku Coast areas
(e.g. Nuaailua Bay, Kauwalu Bay, Wailuanui Bay, and Wailuaiki Bay, southeast of
Papiha Point, Waiohue Bay, Honolulunui Bay, Kipakaone Bay, and Opuhano Bay).
The stream flooding threat is also ranked high at Hana Bay and between Hokuula and
Mokae Cove and Waiaama Bay and Kauakio Bay where the coastal slope is low and
wide stream mouths coincide with coastal embayment and empty into the sea.
High Surf
The most predictable and frequent
coastal hazard in Hawaii is sudden
high waves combined with strong
near shore currents. (Fletcher 2000)
The greatest number of deaths,
injuries and rescues are from the
high surf breaking at the shoreline.
High surf, resulting from dangerous
and damaging waves, is defined by
the Oahu Civil Defense as waves
ranging in height from 10 feet to 20
feet or more. (Fletcher 2000) These waves Provided by Dr. Charles Fletcher, UH SOEST

IV-19
result from storms passing across the higher latitudes of the Northern and Southern
Hemispheres in addition to storms passing across the Pacific in close proximity to the
Islands. These high wave events threaten lives and coastal property. When combined
with high tides and storm surges, high waves can inundate farther inland disturbing
property and infrastructure.
Waves from the north and northwest tend to be the highest on an annual basis and
generally occur several days at a time, most frequently between the months of
October and March. (Fletcher 2000) These swells range between 5 and 10 feet in the
vicinity of Ka’anapali and 10 to 20 feet near Honolua Bay in northwest Maui and along
the North Shore between Waihee and Paia. Occasionally waves of 25 feet and
greater occur over the deep offshore reefs of the North Shore making them popular for
big wave surfing.
Fortunately for Maui, much of its coastline has wide fringing reefs that dissipate wave
energy offshore of its northern and western shores, where wave heights are the
highest. However, areas important for tourism and commerce such as Lahaina,
Ka’anapali, Honokowai, Olowalu, Kihei, and Kahului are sited on low coastal plains,
and therefore experience wave over wash, which causes rapid erosion and
temporarily disrupts transportation along Honoapi’ilani Highway. (Fletcher 2000)
Wave heights along Maui’s southern coast range between 4 to 10 feet. (Fletcher)
Trade wind waves impact the eastern shores 70% of the time. (Fletcher 2000) During
winter storm months, kona storm waves can reach 5 feet along the southern shore
while in the summer months, tropical storms and hurricanes can generate wave
heights of 10 to 20 feet along any portion of the Maui coast (Fletcher 2000).
High waves from winter North Pacific swell; trade wind swell, summer South Pacific
swell, tropical storms and hurricanes, and Kona storms all affect the shoreline of
Moloka’i. Steep sea cliffs east of Kalaupapa Peninsula dominate the north shore. High
waves from north swell, ranging 15-20 feet, are a greater threat to the more accessible
and frequented areas along the north facing shores between Moomoomi and Halawa.
High waves from the trade wind swell range 3-5 feet along the Eastern Shore. Winter
Kona storms create winds and waves from the south and southwest. These waves
can reach heights of 3-6 feet along the south-facing shores.
Damage
Data on high waves and surf in Maui dates as far back as 1896. Much of the high
waves and surf in Maui is attributable to passing hurricanes and tropical storms. Each
year, however, storms passing through the northern Pacific generate wave heights
reaching 15 to 20 feet in the north shore and sometimes up to 30 to 40 feet. Of the
largest wave events occurred February 2-4, 1993 and January 23-31, 1998 when
waves reached heights of 30 and 40 feet respectively. (Fletcher 2000) Wave heights
ranging between 10 and 15 feet reached the north and east shores of Maui as
Hurricanes Susan, Ignacio, and Estelle traveled through the Hawaiian waters.

IV-20
(Fletcher 2000) Along the west shore, wave heights of 6 to 10 feet were recorded as a
result of the passing of Hurricane Emilia to the west in July of 1994.
The most significant amount of losses to Maui occurred during a kona storm,
occurring, January 8-10, 1980. Maui sustained damages over $12.9 million dollars.
Twelve years earlier in April 15 – 16, 1968, the Hana District was declared a disaster
area by the State of Hawaii, a result of 17 inches of heavy rains. Of this total, nearly
16 inches fell within 15 hours, and 1.8 inches fell within 15 minutes. This intensity
categorized this event as a 100-year storm. (Army Corps of Engineers, Storm of 15 –
16 April 1968, Island of Maui, December 1968)
The highest waves that have impacted Moloka’i’s shoreline were generated by tropical
storms and hurricanes that passed by the Islands. Since the 1970’s, several
hurricanes have visited Hawaii; Kate in 1976, Fico in 1978, Pauline in 1985, Iniki in
1992, and Fernanda in 1993. One hurricane of note, Raymond in 1983, passed over
Moloka’i as a tropical depression.
Most recently, Hurricane Fernanda generated high waves ranging 8-10 feet that
damaged one house on East Moloka’i. While no damage was sustained by Hurricane
Iniki, high surf was observed on the east, south and west facing shores. Hurricane
Pauline generated waves of 10-15 feet along eastern shorelines. Hurricane Fico
caused waves of 8-12 feet and Hurricane Kate produced waves of 8-15 feet. Tropical
depression Raymond dropped two inches of rain on the island and generated 10-15
foot surf.
Dam Breaks
A dam is defined as a barrier constructed across a watercourse for the purpose of
storage, control, or diversion of water. (DAM SAFETY MANUAL) A dam impounds
water in the upstream area, or reservoir. The amount of water impounded is
measured in acre-feet referring to the volume of water that covers an acre of land to a
depth of one foot. (FEMA, Multi-Hazards 1997) Two factors influence the potential
severity of a full or partial dam failure: the amount of water impounded, and the
density, type, and value of development and infrastructure located downstream.
There are three types of dams: detention; storage and diversion. Detention dams are
constructed to retard and minimize the effects of flood runoff. These types of dams
are used to store all or a portion of an anticipated flood runoff. The floodwater stored
by the dam is released at a rate that does not exceed the carrying capacity of the
channel downstream. Storage dams are constructed to impound water during periods
of surplus supply for use during periods of drought. This water is critical for crop
irrigation, livestock watering, municipal and industrial water supply and electricity
generation. Diversion dams are constructed to provide hydraulic head for diverting
water from streams and rivers into ditches, canals, or other water conveyance.

IV-21
Maui County has fifty dams. Of these, twenty-one have been rated to be “high”
hazard potential, two is “significant” hazard potential, and four are rated as having a
“low” hazard potential. Of the 50 dams, twenty-three have not been rated. All of
Maui’s dams are made of earth.
Disastrous floods caused by dam failures, may cause great loss of life and property
damage, primarily due to their unexpected nature and release of a high velocity wall of
debris-laden water rushing downstream destroying everything in its path.
Dam Hazard Potential Classification
Category Loss of Life Property Damage
Low None expected Minimal (undeveloped to occasional
structures or agriculture)
Significant Few (no urban structures) Appreciable (notable developments and
or inhabitable no more than a small number of inhabitable
structures, agriculture, industry
High More than a five Excessive (extensive community, industry,
or agriculture)
The 1997 FEMA Multi-hazards Identification and Risk Assessment Publication reports
that dam failures can result from anyone or a combination of factors:
?? Prolonged periods of rainfall and flooding;
?? Inadequate spillway capacity;
?? Internal erosion resulting in structural failure
?? Improper maintenance
?? Improper design;
?? Negligent operation;
?? Failure of upstream dams on the same waterway;
?? Landslides into reservoirs which may cause surges resulting in overtopping;
?? High winds which can cause significant wave action resulting in substantial
erosion; and
?? Earthquakes, which cause longitudinal cracks and weaken the entire structure.
Land Slides/Debris Flows
A landslide happens when gravity
forces land downward, often due to
precipitation, runoff, or ground
saturation. Debris flows, sometimes
referred to as mudslides, mudflows,
lahars, or debris avalanches, are
common types of fast-moving
landslides and occur in a wide variety
of environments. These flows

IV-22
generally occur during periods of intense rainfall, but can also be triggered by seismic
activity or prolonged dry periods.
The consistency of debris flow ranges from watery mud to thick, rocky mud that can
carry large items such as boulders, trees, and cars. Debris can also include larger
rocks and even boulders causing extensive damage. Debris flows from many different
sources can combine in channels where their destructive power may be greatly
increased. They continue flowing down hills and through channels, growing in volume
with the addition of water, sand, mud, boulders, trees, and other materials in its path.
When the flows reach flatter ground, the debris spreads over a broad area, sometimes
accumulating in thick deposits that can wreak havoc in developed areas. Once
started, however, debris flows can travel even over gently sloping ground. The most
hazardous areas are canyon bottoms, stream channels, areas near the outlets of
canyons, and slopes excavated for buildings and roads.
Several features on land may be noticeable prior to a landslide. These features
include:
• Springs, seeps, or saturated ground appears in areas usually not wet
• New cracks or unusual bulges in the ground, street pavements, or sidewalks
• Soil moves away from foundations
• Ancillary structures (e.g. decks, lanai) tilt or move relative to the house
• Concrete floors or foundations tilt or crack
• Water lines and other underground utilities break
• Telephone poles, trees, retaining walls, or fences tilt
• Road beds sink, or drop down
They are particularly dangerous to life and property because of their high speeds and
the sheer destructive force of their flow that is capable of destroying objects in their
paths, and often strike without warning. Landslides usually start on steep hillsides as
shallow landslides that liquefy and accelerate to speeds that are typically about 10
mph, but can exceed 35 miles per hour. These flows are capable of destroying homes,
washing out roads and bridges, sweeping away vehicles, knocking down trees, and
obstructing streams and roadways with thick deposits of mud and rocks.

IV-23
Coastal Erosion
“Today’s coastline is of economical, social, cultural, and environmental
value to communities and to nations. However, shorelines are dynamic
and ephemeral places where erosion trends tend to dominate.
Development along the shore places the desires of man (to have a safe
and stable home) in direct opposition to the natural trends of nature (to
erode, transport, and deposit coastal lands).”
Joan Pope, U.S. Army Corps of Engineers
The Natural Course of a Beach Life Cycle
Coastal zones are dynamic areas that are constantly undergoing change in response
to a multitude of factors including sea level rise, wave and current patterns,
hurricanes, and human influences. Despite the fact that Hawaii appears to have a
well-developed and comprehensive governmental system in place to respond to
coastal erosion and beach loss, beach loss still occurs in great proportions in Maui.
High winds and associated marine flooding from storm events such as Kona Storms
and hurricanes, flooding, tsunami flooding, sea level rise, seasonal high surf, stream
flooding on coastal plains, landslides, and
seismic and volcanic hazard all increase
the risk exposure along developed coastal
lands. Storm impacts and long-term
erosion threatens developed areas with
potential loss of life and billions of dollars
in property damage. In addition to the
natural processes that cause erosion,
human alterations are affecting erosion
rates. Human interference with sand
transport processes underlies much of the
chronic erosion impacting portions of the
Maui shoreline.
Erosion has been wearing away beaches and bluffs along the U.S. coastal and Great
Lakes shores from the powers of flooding, storm surge, rising sea levels, and high
surf. As shorelines retreat inland, waterfront homes, public infrastructure such as
roads, bridges, wastewater treatment facilities, and storm water drainage systems
eventually may become severely damaged beyond use, uninhabitable, or surrender to
the powers of the sea. The Heinz Center Report on “Evaluation of Erosion Hazards”
predicts that over the next 60 years erosion may claim one out of four houses within
500 feet of the U.S. shoreline. Most of the damage will occur in low-lying areas also
subject to the highest risk of flooding. Some additional damage will also occur along
eroding coastal bluffs.
Maalaea

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The beaches of Hawaii are vital economic, environmental, and cultural resources. A
healthy, wide sandy beach provides protection against the effects of storm surge,
tsunami flooding, and high surf impacts. The beach environment provides habitat for
marine and terrestrial organisms with beach dependent life stages and is home to
species of indigenous and endemic Hawaiian plants. Beaches are also the basis for
the visitor industry, exceeding by a factor of three all other industries combined when
providing direct income to the State. (DLNR, Coastal Erosion Management Plan,
2000)
Beaches change their shape, depth, and slope in response to wind, wave, and current
forces, and the availability of sand. The sources and sinks of sand within a particular
beach system and the mechanisms by which they affect the beach morphology are
often cumulatively referred to as the sediment budget of the beach. Seaward sources
of sand to the sediment budget of a beach include long shore currents moving sand
along the coast and cross shore currents moving sand onshore. Landward sources of
beach sand include dunes, ancient shorelines, and other onshore sand deposits that
release sand to the beach by the forces of the wind and waves. High waves will cause
a beach to change its shape, or profile by redistributing sand across the shoreline.
Maui’s beaches serve as natural protective buffers between the ocean and the land.
Waves reaching Maui from storms across the Pacific carry tremendous amounts of
energy, and beaches absorb much of this energy before it reaches the shoreline and
coastal properties. During storm events, a beach is able to modify its slope and overall
morphology to dissipate the waves while not destroying itself. The beach profile is
flattened, and the waves coming inshore shoal further out offshore, thus minimizing
further erosion. Beaches recover when sand is moved back onto the shore by smaller
waves, and then is blown inland to reestablish the frontal dunes. The final stage of
recovery of the beach and dunes occurs when vegetation grows back over these new
dunes. Hence, the narrowing of healthy beaches in response to a high wave event is
often a temporary condition. (Beach Management Plan for Maui 1997, Rob Mullane
and Daren Suzuki)
Coastal Erosion vs. Beach Erosion
It is important to understand the difference between coastal erosion and beach loss.
Coastal lands may experience long-term erosion under some conditions. For instance,
if sea level is rising, the beach must eventually migrate landward or drown. This
causes coastal land behind the beach to erode. The beach then, remains wide and
healthy as it moves with the eroding coastline. If sand is not available to a beach on a
chronically eroding shoreline, then beach erosion will ensue, leading to narrowing and
eventually beach loss. Beach narrowing and loss occurs where sand supplies are
diminished or discontinued. Beaches on eroding coasts still undergo seasonal profile
adjustments, but they slowly shift their position landward as the land erodes.

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Chronic Erosion
Chronic erosion may also be caused by repeated episodes of high surf constantly
drawing sand stores from the upland area of the beach to feed the beach profile.
Along most Hawaiian shorelines, sands stored in dunes and fossil shorelines are
moved onto the beach by this process. Beaches benefit from this source of sand, in
order to remain wide and healthy, even as the land behind them may erode. Chronic
erosion, then, causes land loss, not beach loss. Armoring, or hardening of the
shoreline with seawalls and revetments to stop chronic coastal land loss, often
refocuses wave forces onto the beach in front of the seawall. Beach erosion ensues,
leading to a volumetric loss of sand that result in beach narrowing and eventually
beach loss. (Beach Management Plan for Maui, 1997; COEMAP 2000)
Episodic Erosion
Episodic erosion is also a concern for many of Maui’s beaches, especially those
lacking a fringing reef and exposed to seasonally high waves. On these beaches a
single unusually large wave event or high wave season can cause severe coastal
erosion. The vegetation line may retreat as much as 60 or more feet, but if the erosive
event is followed by a long period of normal wave conditions, the shoreline can
recover, often accreting back to its pre-event location. Beaches subject to rapid
erosion and accretion cycles are referred to as dynamic (Makai Ocean Engineering
and Sea Engineering, 1991). There may be little or no long-term trend of shoreline
erosion, but the risk of episodic erosion remains.
Effects of Local Wind and Surf Patterns
Highly variable local patterns of wind and wave dynamics can be important keys to
dispelling misunderstandings of beach processes. Waves are the key factor in the
process of coastal retreat because they are able to reach high onto the beach and into
the dunes during certain seasons of the year when they are at their maximum height.
This reach allows sand to be transported back to the beach face to “make deposits
into the beach sand budget.” In general, on the north shore of Maui, waves are highest
in the winter because they are generated by distant storms in the northern Pacific. On
the south side, waves are highest in the summer because they are generated by
storms in the Southern Hemisphere. On the windward shores, waves are generated
by strong trade winds and by large north swell that wraps around the coastline.
Natural features such as coral reefs, offshore channels, and offshore depth variability,
as well as the orientation of the coast relative to the prevailing winds and approach of
distant waves, drive waves in different ways. For example, the beaches in South Maui
are influenced by trade wind-driven flow so that sand typically moves to the south. But
when intense “Kona” storms from the south and west occur there, sands are driven to
the north in large quantities. (COEMAP 2000)

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Sediment Deficiencies
There are situations that call for human interference with patterns of sand flow and
accumulation. These include clearing storm drainage channel mouths, dredging
harbors and boat basins, widening harbors or extending breakwaters, crossing the
shoreline with outfall pipes, or cutting new channels. These and other activities that
are common on the Hawaiian shoreline have the potential to cause sediment
deficiencies along adjacent beaches. It is important to conduct a careful assessment
of dynamics and patterns along the shoreline in question in order to minimize impacts
to coastal resources. Moderate erosion trends can be exacerbated and accreting
coastlines caused to erode by poorly conceived civil works projects on the coast that
trap sand or alter its movement.
Sand Mining
In the past, Maui’s beaches have been subjected to sand mining for lime processing.
The calcareous sand (CaCO3) is baked to release carbon dioxide and produce simple
lime (CaO) for use as a building material. Baldwin Beach, Sugar Cove, and other
beaches were past sand mining sites on Maui. Sand mining is in large part
responsible for the retreat of both the vegetation line and the beach foreshore over
recent decades along these beaches. Sand mining will result in obvious negative
impacts to beaches by decreasing sand volumes, steepening the morphology of the
shoreline, and reducing the ability of profiles to respond to seasonal wave stresses.
Although presently outlawed in Hawaii, there are occasional requests to mine remote
beaches that are perceived as being of low socioeconomic value and high sand
volume.
Coastal Armoring
Sediment impoundment accompanies coastal armoring. Sands that would normally be
released into coastal waters during high wave events and with seasonal profile
fluctuations are trapped behind walls and revetments
and prevented from adding to the beach sediment
budget. One wall may have minimal impact, but
along many Hawaiian coastlines myriad armoring
types combine to reduce sand availability to nearly
zero. Natural coastal erosion does not damage
beaches that have access to a robust sediment
budget. Beaches on chronically eroding coasts that
are not armored remain healthy even during
shoreline retreat because sands are released from
eroding coastal lands that nourish the adjoining
beach. Armoring traps those sands and a sediment deficiency develops, such that the
beach does not withstand seasonal wave stresses and begins to narrow with time.

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Chronic beach erosion and beach loss eventually results. Many beaches eventually
disappear simply because they are starved of sand.
Dune Grading
One of the most important storage sites for
sand is the frontal dune system that lines many
shores and armoring traps these sands.
Additionally, the leveling and grading with
topsoil that accompanies housing construction
on beachfront lots is one of the most
destructive practices taking place along the
Hawaiian coast. Dune ecologies in Maui have
been decimated by common landscaping
practices that do not seek enhancement of the
endemic environment, do not recognize the
value of salt tolerant vegetation as a tool for
beach and dune preservation, and do not establish dune conservation as a goal of the
landscaping effort. Soil filling to support short-grass lawns is a source of siltation to
coastal waters during erosion events, and acts to compact and trap dune sands such
that the adjacent beach experiences deflation, or a lowering of elevation due to sand
removal by waves without replacement by dune sand. Deflated beaches fronting filled
dunes provide poor erosion buffering capabilities and are themselves a degraded
environment with little to offer the normal coastal ecosystem and its host of organisms
with beach-dependent life stages (turtles, various marine larvae, and certain reef
fishes).
Canalization
Many streams that flow intermittently from
our mountains to the coast are subject to
flash flooding during heavy rainfall events.
To prevent coastal zone flooding, the most
hazardous of these streams have been
canalized into concrete canals or gutters
so that flooding is contained. Where these
open onto the coastal zone, the channel
mouths tend to trap sand that is moving
along the shoreline. The buildup of sand
within the channel mouths increases the
upstream flood hazard and creates a sand
deficiency on the adjacent beach. Public works departments often clear these
accumulations and dispose of the sand in various ways, including trucking it off-site to

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be used elsewhere (i.e. golf courses). Unless these sands are returned to the
immediate beach area, the long-term dredging and clearing is nothing less than a
sand-mining effort and it will have a similar impact on the adjacent beach. This has the
potential to reduce available sand volumes and create chronic erosion where none
previously existed. In placing cleared sands onto adjacent beaches it is important to
be aware of prevailing sediment transport patterns so that returned sand can function
in a manner that will provide nourishment. To ensure this, it will be necessary to
conduct a review of the ambient littoral processes and develop schedules of transport
direction around each channel mouth, with guidelines on the placement of returned
sand.
Past and Recurring Damage
John Rooney at University of Hawaii SOEST has provided the following descriptions
with input also from Rob Mullane and Matt Niles of Hawaii Sea Grant.
South Maui – Kihei
Along the Kihei coastline there is a general trend of erosion, but with widely varying
rates and patterns of shoreline movement through time. There have also been major
decreases in the width of the beach along the Kalama Park/Halama Street area where
the beach has mostly disappeared in front of coastal armoring. Problems related to
coastal and beach erosion has arisen along this coastline as a result of people
building too close to the shoreline to accommodate natural shoreline fluctuations. The
dynamic nature of shorelines is often much greater than people realize. The shoreline
at the south end of Kalama Park receded a maximum of about 100 yards between
1912 and 1949, and accreted a maximum of about 115 yards between 1900 and 1949
a quarter mile south of the Whale Sanctuary Building. Beaches prone to episodic
erosion include Keawakapu Beach, Mokapu Beach, Palauea, and Poolenalena; all of
which suffered severe erosion during the Kona storms of 1980 and 1982.
Although most of the Kihei shoreline appears to have been much less dynamic over
the past century, development and infrastructure has often been sited far too close to
the ocean. For example, some of the resort hotels in the Sugar Beach area were
constructed in the dynamic zone of the beach, seaward of the 1949 vegetation line. In
addition to the obvious risk of property damage, Maui County may incur liability for
issuing construction permits in areas that can be reasonably expected to be subject to
erosion damage over the expected lifetime of the structures.
North Maui – Kanaha
Kanaha Beach, on Maui’s north shore, is part of about a 5 mile stretch of coastline
between Kahului Harbor and Paia that has been experiencing severe erosion since at
least 1950. Mining of beach sand for processing sugarcane in years past has
undoubtedly contributed to the problem. It has been suggested that construction of
Kahului Harbor in 1910 may be contributing to the problem as well. A wastewater

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facility serving the Kahului-Wailuku area was constructed here in the mid-1970s,
despite an obvious erosion hazard, and is today protected by a rock revetment. This
and the revetment built to protect the lime limn at Baldwin Beach have resulted in loss
of the beach in front of these structures. Wide beaches despite severe coastal
erosion, however, front adjacent, undeveloped shoreline segments. Numerous groins
in the area appear to have slowed movement of sand along the shoreline in some
areas, but often have led to increased erosion rates along down drift areas. A study of
coastal sediment transport and the impact of Kahului Harbor may possibly suggest
ways to mitigate coastal erosion here. However, the area is subject to high wind and
wave energy despite the wide fringing reef offshore. The presence of what appear to
be a series of beach rock ridges up to 800 feet offshore suggest that severe erosion
has been occurring here for far longer than have western impacts to the coast.
West Maui
Along much of the West Maui coastline from Papalaua to a couple miles south of
Lahaina, Honoapiilani Highway runs right along the ocean. Although this offers nice
view planes, in several areas the highway is situated dangerously close to the ocean
and interferes with active beach processes. The beaches and offshore reefs along
here are valuable resources heavily used by both residents and visitors. These
resources are being damaged in some cases, and threatened in others, by proximity
of the highway. Revetments and seawalls armor several short segments of the
highway, but nonetheless, many of these segments are still subject to coastal flooding,
wave splash, and wave overtopping. Wave run-up during both moderate and large
wave events floods portions of this highway, leading to occasional temporary road
closures. These closures create unsafe driving conditions when traffic unexpectedly
comes to a halt.
Wind Hazards
Wind is one of the most costly insured property perils, causing more damage than
earthquakes, freezing, or other natural perils. (IIPLR, 1994) In most wind storms, but
especially in hurricanes, windborne debris can be a major factor in causing damage.
Flying objects such as tree limbs, outdoor furniture, signs, roofs, gravel, and loose
building components from progressively failing adjacent buildings can impact the
building envelope, creating openings that allow internal pressure to build within.
Wind Pressure
Internal pressures develop within a building when the building envelope is breached.
The breakage of window glass or the failure of an overhead door commonly causes
the breach in the envelope. The internal pressures add to the external pressures
producing more severe pressures on the building components of the structure. (IIPLR,
1994) The roof then feels tremendous internal pressure building from inside, together
with the negative wind pressures lifting the roof from outside. The resulting combined

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forces may be too large, even for good roofs if the roof has not been designed for
them. After the roof is gone, high winds and rain destroy the inside of the structure.
Wind is defined as the horizontal component of natural air moving close to the surface
of the earth. (David Ludlum1982) Wind pressure, not wind speed, causes wind
damage. (IIPLR1, 1994) There are three types of wind pressure: positive, negative,
and internal.
• Positive wind pressure is what one feels when the wind is blowing in one’s face. It
is the direct pressure from the force of the wind that pushes inward against walls,
doors and windows.
• Negative wind pressure occurs on the sides and roof of buildings. It is the same
pressure that causes an airplane wing to rise. This negative pressure is also
known as lift. Negative pressure causes buildings to lose all or a portion of their
roofs and side walls, and pulls storm shutters off the leeward side of a building.
• Interior pressure increases dramatically when a building loses a door or window on
its windward side. The roof fells tremendous internal pressures pushing up from
inside of the building together with the negative wind pressure lifting the roof from
the outside.
Wind Speed
It is often difficult to obtain accurate and consistent wind speed measurement during
most storms. Wind speed measuring devices, anemometers, often become damaged
from wind and airborne debris when severer wind storms occur. It is important to
understand the effect of winds on buildings. Wind speeds vary with height above
ground, the higher the elevation, and the stronger the wind (IIPLR, 1994)
• The Fastest Mile Wind is the wind speed used in the American Society of
Civil Engineers (ASCE) national wind speed standard. This measurement is
taken at an elevation of 33 feet in open terrain and is the highest recorded
speed during a time interval in which one mile of wind passes a fixed
measuring point. At 60 miles per hour this is a 1-minute average wind.
• Sustained Wind is the wind speed averaged over 1 minute.
• Peak Gusts are averaged over two to five seconds.
Wind Patterns
Trade winds are by far the most common winds over Hawaiian waters and play a
major role in defining the climatology of the region. (Kodama 1998). These persistent
winds, which blow from a NE to ENE direction, became known as trade winds long
1 IIPLR the Insurance Institute for Property Loss Reduction knows the Institute for Business and Home Safety.

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ago when clipper ships carrying cargo depended on the broad belt of Easterly winds
encircling the globe in the subtropics for fast passage. (Kodama 1998)
Though pleasantly brisk and refreshingly cool on land, strong, gusty trade winds can
cause problems for mariners. These strong trades blowing from the NE through East
funnel through the major channels between the islands--Kauai, Kaiwi, Pailolo, Kalohi,
and Alenuihaha Channels--at speeds 5-20 knots faster than the speeds over the open
ocean. North Pacific High-pressure systems are responsible for the majority of the
gusty trade wind episodes over Hawaiian waters, which commonly persist for several
days before tapering off. Mariners and beachgoers must exercise good judgment prior
to entering the waters exposed to strong trades, especially in the major channels.
High winds from trade winds, which blow 70% of the time, Kona winds 30% of the
time, and winds from hurricanes and tropical storms passing through Hawaiian waters
all affect the Island of Maui County. (Fletcher 2000) Trade winds predominate from
the northeast and generally range from 10-25 miles per hour, although occasional
extreme events reach 40-50 miles per hour when the sub-tropical high-pressure cell
north of the islands intensifies. (Fletcher 2000) Trade winds appear to be stronger
when passing through the isthmus between West Maui and Haleakala, so that wind
speeds at Maalaea and north Kihei may be higher than along the North Shore. This is
the result of wind funneling which often occurs when wind passes between two
mountains or into a valley.
The most damaging winds are those associated with passing tropical storms and
hurricanes. East-facing coastlines in Hawaii generally receive the brunt of tropical
storm winds as the storms approach the islands. The south and west facing shorelines
often feel strong winds and waves derived from these storms as they pass to the west.
Occasionally when such storms track to the east of the Islands, the north shores are
impacted. In all cases, acceleration of wind down slope often occurs such that the
highest winds may in fact be recorded on the leeward side of the wind approach.
Since 1871, at least forty-seven strong wind events have impacted the entire island of
Maui. Of these, thirty-four were associated with extreme trade winds and/or Kona
storm winds, while thirteen occurred during passing tropical storms and hurricanes.
The strongest trade wind events hammered the north and east shores with winds of
40-60 mph. High southerly Kona storms have hit Maui with speeds of 40-50 mph on
several occasions. Maui has only been brushed by a tropical depression and never hit
by a hurricane. It has, however, sustained some damage from the impact of winds
from both. Hurricane Nina, for example, brought gusts greater than 90 mph to parts of
Maui in November 1957.
The most damaging high winds to affect either Moloka’i or Lana’i were those
associated with tropical storm Sarah in 1971 and Die Deutsche Seewarte III in 1874.
These both destroyed a number of houses.

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History of strong winds and hurricanes on Maui
DATE DESCRIPTION
August 9, 1871 Kohala Cyclone, gale winds
December 7, 1896 Strong winds
January 21, 1906 High winds
October 2-9, 1906 Makawao Cyclone
January 14, 1916 High winds
August 18-19, 1938 Mokupu Cyclone
January 17, 1948 High winds
January 23-26, 1948 High winds
December 21, 1955 High winds
November 30-31, 1957 Hurricane Nina, gusts to 92 mph.
August 6-9, 1958 Tropical Storm
January 17-18, 1959 Storm
August 4-7, 1959 Hurricane Dot, strong winds
January 15-17, 1963 Strong winds
January 30-31, 1963 Strong winds, gusts to 84 mph.
September 12-19, 1963 Tropical Storm Irah, strong winds
December 19-23, 1964 Strong winds
August 8-10, 1967 Tropical Storm
November 2-11, 1967 High trade winds
December 9, 1967 High winds
December 12, 1967 Strong winds
December 5-6, 1968 Storm
February 20-21, 1969 Strong winds
December 25-29, 1970 High winds, 50-60 mph.
January 5, 1971 Strong winds
November 23-27, 1975 Storm
February 5-7, 1976 Storm
January 11-19, 1979 High winds, 50+ mph.
January 8-10, 1980 High winds
July 21-22, 1982 Tropical Storm Daniel
August 1, 1982 Tropical Storm Gilma
December 19-19, 1982 Strong gusty trade winds
October 15-20,1983 Hurricane/Tropical Depression Raymond
December 24-26, 1983 Strong winds, 50 mph gusts.
December 24-25, 1984 Kona Storm
March 1-11, 1985 Gale force trade winds
July 22-23, 1986 Hurricane Estelle
November 4-5, 1988 Storm gusts 40-50 mph.
December 5-6, 1988 Storm, southerly winds to 50 mph.
December 17-18, 1988 Gusty winds
December 30-31, 1988 40-50 mph winds.

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March 1-4, 1989 Storm, strong winds
December 9-11, 1989 Gusty winds
January 27, 1991 Strong winds
December 4-6, 1993 Strong trade winds 60-80 mph.
December 23-25, 1996 Southwest winds 40 mph.
January 27-28, 1997 South-southwest winds
Hurricanes
One of the most dramatic, damaging and potentially deadly events that occur in the
Hawaii is a hurricane. A hurricane is defined as a large circulating windstorm covering
hundreds of miles that forms over warm ocean water. To be officially classified as a
hurricane, the wind speeds must exceed 74 miles per hour. The maximum winds in a
hurricane occur near a calm eye and diminish with distance from the eye.
During a hurricane, high winds, marine over wash, storm surge and small scale wind
bursts may damage or destroy homes, businesses, public buildings and infrastructure.
Termed “microbursts” and mini-swirls, these localized winds may reach wind speeds
in excess of 200 miles per hour. (Fletcher 2000) During Hurricane Iniki, damage
patterns and debris indicated that there were more than 26 mircobursts (sudden
intense downdrafts) and two miniswirls (a violent whirlwind, not tornado) had occurred
on Kauai (Fletcher 2000).
In the northern Hemisphere, the winds circulate in a counter clockwise direction
(clockwise in a southern hemisphere). A great dome of water as much as 50 miles
across called the storm surge is pushed ahead of the storm by its winds. (Keillor and
Miller, 1987). This can result in tides 20 feet or more higher than usual. Storm surge
is responsible for many hurricane-related deaths and for coastal erosion.
In addition to severe winds, hurricanes have several other characteristics. Barometric
pressure is very low, for example, usually 29 inches of mercury or less. Hurricane
winds are directly related to the lowest barometric pressure reading at the center of
the storm. (IIPLR, 1994) Hurricane winds are strongest near the Radius of Maximum
Winds, the area within the storm path near the lowest central pressure. (IIPLR, 1994)
The larger the radius, the larger the area of maximum destruction. The strongest
winds are usually on the right side of the eye, as one faces the direction the storm is
moving. (IIPLR, 1994) Wind speeds decrease as the distance away from the radius of
maximum winds increase.
During a hurricane, high winds, storm surge and rains may damage or destroy homes,
businesses, public buildings and infrastructure. Flying debris can break windows and
doors, unsealing the building "envelope" and creating extensive damage inside the
structure. After the roof is gone, high winds and rain destroy the inside. Roads and
bridges can be washed away by flash flooding or blocked by debris. In extreme
storms, such as Hurricane Iniki, the force of the wind alone caused tremendous

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devastation, as trees and power lines toppled and weak elements of homes and
buildings failed. These losses are not limited to the coastline; they can extend
hundreds of miles inland under certain conditions (FEMA,1997).
Hurricane Intensity
The Saffir-Simpson scale measures hurricane intensity. Number and range from 1
(low) to 5 (high) categorize storms. A hurricane’s approximate damage potential
increases as the square of the integer value for the Saffir-Simpson category. (IIPLR,
1994) The wind speed of a hurricane decreases as it moves inland for two reasons.
First, the major source of storm energy (warm water) is no longer available to fuel the
storm. Second, the land, vegetation, and structures offer frictional resistance to the
storm winds. A hurricanes’ peak wind speed distribution is a direct function of its
rotational wind speed and forward speed. Storms that have a higher traveling speed
do not stay in one place for long, minimizing the possibility of damaging buildings and
other stationary structures. However, faster moving storms tend to be more
destructive further inland. Because they travel further inland causing higher storm
surge and stronger winds. (IIPLR, 1994).
Saffir Simpson Hurricane Intensity Scale
Category Wind Speed Damage Potential
1 75 – 95 mph Minimal damage to vegetation. No real
damage to other structures. Some damage to
poorly constructed signs. Low-lying coastal
roads inundated, minor pier damage, some
small craft in exposed anchorage torn from
moorings.
2 96 – 110 mph Considerable damage to vegetation; some
trees blown down. Major damage to exposed
mobile homes. Moderate damage to houses.
Considerable damage to piers; marinas
flooded. Small craft in unprotected anchorages
torn from moorings. Evacuation from some
shoreline residences and low-lying areas
required.
3 111 – 130 mph Large trees blown down. Mobile homes
destroyed. Extensive damage to small
buildings. Poorly constructed signs blown
down. Serious coastal flooding; larger
structures near coast damaged by battering
waves and floating debris
4 131 – 155 mph All signs blown down. Complete destruction of
mobile homes. Extreme structural damage.

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Major damage to lower floors of structures due
to flooding and battering by waves and floating
debris. Major erosion of beaches.
5 >155 mph Catastrophic building failures. Devastating
damage to roofs of buildings. Small buildings
overturned or blown away.
Storm Tracks in Hawaiian Islands
The most typical storm track near
Hawaii is toward the
west/northwest. This is consistent
with the large-scale winds that
steer the storms. Hawaii lies at a
longitude near to that of the center
of the subtropical high which drives
the trades. As storms pass Hawaii
they will naturally curve to the
northwest unless the high extends
usually far to the west. In the
trades, winds turn to the south with
height contributing to a
southeasterly steering wind. In the
upper troposphere, the winds over
the islands are southwesterly and
contribute to north turns as well
(Schroeder, 1993)
The Myth of Maui
A common myth in Hawaii is that the islands of Hawaii, those in Maui County, and
Oahu are less vulnerable to a direct hit by a hurricane than Kauai. This myth has
developed as a result of the fact that, until 1950, tropical storms hitting Hawaii were
not classified as hurricanes and it was not until the advent of weather satellites that
the nature of storms in this part of the world were understood to be hurricanes.
We know that since 1950 five hurricanes or tropical storms have caused se