County Profiles
State and county partnerships to facilitate place-based shoreline management strategies
Overview
Hawaiʻi's Coastal Zone Management (CZM) Program is responsible for managing the State's coastal and marine resources. While the Office of Planning and Sustainable Development (OPSD) is the lead agency, the CZM Program is a collaborative network of agencies and partners whose mandates and regulations work to preserve, protect, develop, and where possible, to restore or enhance the resources of Hawaiʻi's coastal zone.
At the local level, Counties are key partners and serve as the authorities to administer and enforce special management area (SMA) permitting and shoreline setbacks. OPSD-CZM provides financial support and assistance, including oversight and guidance in SMA permitting, to the County SMA Authorities and Planning Departments. By having this networked approach, the CZM program is able to consider each county's unique characteristics when addressing challenges and vulnerabilities.
Various government entities, including state, federal and county agencies, are involved in shoreline management. In the following profiles, we focus specifically on the partnership between OPSD-CZM and the County Planning Departments. Between and within each county, the variation in demographics, shoreline characteristics and coastal hazards means there is no one-size fits all solution to shoreline management. Instead, the partnership between OPSD-CZM and the County Planning Departments emphasizes the use of place-based strategies to address challenges in Hawaiʻi's shoreline management.
Kauaʻi County
Demographic Statistics:
Demographic statistics comparing Hawaiʻi State to the various counties, highlighting Kauaʻi County (Source: US Census Bureau).
Shoreline Characteristics Overview:
Kauaʻi County, consisting of Kauaʻi and Niʻihau islands, is the most northern county in the State and the oldest of the currently inhabited islands. While the island of Kauaʻi's 145 km of coastline is only 12% of the State’s total coastline, it has over one-third of the State’s sand and over 75 km of sandy beaches. Due to its round shape and lack of nearby islands, Kauaʻi is highly exposed to waves, swells, winds and storms from all directions.
The North coast (Nā Pali Coast State Park to Moloa‘a) region is characterized by sandy bays backed by steep mountains. Offshore, from Kalihiwai Bay to Princeville is one of the largest shallow fringing reef systems in the State. The northwestern part of the coast sits at the base of the Nā Pali Coast State Park and is extremely rugged and not easily accessible.
The East coast (Moloa‘a to Maha‘ulepu) is a mix of embayments and rocky headlands. Many of the bays contain river and stream mouths, leading to high volumes of freshwater discharge during storms. Offshore is an extensive and well-developed fringing reef.
The South coast (Maha‘ulepu to Port Allen) is a continuation of sandy beaches and rocky headlands. The eastern end of the coast is undeveloped coastline with sand dune systems. The southern most tip, around Poipu, is a tourist center with resort development around pocket beaches.
The West coast (Port Allen to Polihale), the Mana Plain, is sand-rich with an extensive dune system. The beaches are wide and gently sloping. Long, narrow beaches can be found on the southern end of the coast, along with sediment off-loading from the Waimea River.
Coastal Management Challenges and Strategies:
Due to its diverse coastal habitats and shoreline uses, the County of Kauaʻi faces a variety of challenges when it comes to managing the shoreline. The County Planning Department, with support from OPSD-CZM, is taking steps to not only address current issues, but also proactively manage the coastline to mitigate future impacts. The map below features a select set of areas that exemplify some of the County's challenges and management strategies.
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Hanalei Flooding
In April 2018, Kaua‘i experienced record-breaking rainfall on the island's windward coast. Catastrophic flooding affected the entire north shore, and communities from Hanalei to Hāʻena were isolated for over a year due to severe damage to the only highway. Over the years, parts of the community have been able to recover and build back better. For example, in Hanalei, the flood washed away bathroom and parking facilities at Black Pot Beach Park, and blocked road access to many homes. Large flood channels were carved into the land and historical sand deposits from the Hanalei River were washed out into the Bay. As a result, areas of lost park facilities and private homes were filled in with large lagoons, many of which were contaminated by septic systems and other pollutants brought down through the watershed.
In partnership with Hawai‘i Sea Grant and the UH Coastal Geology Group, the County of Kaua‘i conducted an aerial survey and found that 79,000 cubic yards of sand were deposited into the nearshore area of the Bay after the flood. Kaua‘i County Public Works’ restoration plan recovered 20,000 cubic yards of sand to fill in the contaminated flood channels and redesigned the parking area to block cars from accessing the beach. These changes will make the park more resilient to future flooding events, as well as support overall beach health. The park reopened in 2019.
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Progressive Shoreline Setback Standards
Hawaii State Law’s shoreline setback policy restricts construction seaward of the designated setback line, which can be no less than 40 feet from the shoreline (HRS § 205A-43). In a proactive approach to shoreline management, the Kaua‘i County Council has passed several ordinances to exceed these minimum requirements. The minimum setback requirement was increased to 60 feet for all coastal properties, making it one of the most progressive in the nation. This designation was based off science-based rates established in the Kaua‘i Coastal Erosion Study, and current coastal hazard mitigation best practice strategies. Additionally, property owners wanting to pursue construction within the shoreline setback are required to sign a “coastal hazard disclosure statement” in addition to their application for shoreline setback determination.
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Incorporating Coastal Resiliency in the West Kaua‘i Community Plan
From 2018 to 2020, the Kaua‘i Planning Department conducted community meetings and studies to update the West Kaua‘i Community Plan. The Plan, which serves as a guide for the County’s land use decisions and infrastructure investment priorities, incorporates climate change and sea level rise data to build-in coastal resiliency and preventative measures. The plan designated certain vulnerable areas as Special Treatment Coastal Edge (ST-CE) districts. Uses and structures within ST-CE districts must undergo a permitting process and incorporate additional mitigation measures. Currently, the Kaua‘i Planning Department is working on developing the regulations and mitigation requirements. The Department may seek to designate other areas of Kaua‘i as ST-CE districts in the future.
The updated Plan also established Plantation Camp Zones which allows existing, non-conforming residences greater flexibility to repair and rehabilitate structures. Plantation Camp Zones that are subject to coastal hazards are allowed to rearrange density within the property to mitigate for potential risk.
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Waimea Town
The historic town of Waimea is flanked by Waimea Canyon and a black sand beach. The buildings and land use are a result of the town’s rich plantation history. As a low-lying town, areas of downtown Waimea, makai (towards the sea) of Kaumuali‘i Highway will become increasingly exposed to sea level rise. In a scenario of higher sea levels, annual high wave runup would be the dominant hazard, and rising groundwater levels will become an increasing concern.
To protect from these vulnerabilities, there are opportunities to build and adapt structures that would accommodate for wave runup, such as elevating existing buildings, adding “freeboard” standards to floodplain ordinances, and Low Impact Development standards (LID). Areas mauka (towards the mountains) of Kaumuali‘i Highway and west of Waimea Town are the least exposed to hazards, making them potential sites for future development or retreat.
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Wailua Beach
The Wailua Beach corridor is an incredibly important link to Kaua‘i’s east side and north shore. Kuhio Highway and the Wailua Bridge serve as the only access to these parts of the island. The highway hugs the Wailua Beach coastline, leaving the road and surrounding communities vulnerable to beach erosion, sea level rise, and storms. Wailua Beach has a history of large episodic erosion events followed by periods of recovery, however sea level rise threatens to hinder those recovery events. The challenges in this area exemplify the crises created by rising sea levels and the challenges with the state’s aging coastal roadway infrastructure.
Recently, in winter 2019 unusual high tides combined with persistent trade wind swell and storms initiated a long period of erosion at Wailua Beach. In November 2019, accelerated erosion starting near the north parking area and extending south, critically undermined sections of the parking area, vegetation, trees, boulders, shower, and parts of the multi-modal path. The south end of the beach, near the Wailua river mouth, began to erode significantly during summer 2020.
In 2020 Hawai‘i Department of Transportation (DOT) installed a revetment to protect the bridge abutments, in 2021 emergency sand bags were installed to protect portions of the highway and bike path, and the State and currently plans to further armor this coastline. Shoreline armoring is known to cause beach erosion and eventual loss, and this is the concern for the future of Wailua Beach. However, with no immediate plans to relocate the highway or bridge, armoring is the avenue currently being pursued to protect the State’s infrastructure. DOT is exploring new technologies and a pilot project promote sand accumulation on the beach, however it is unknown whether these will be successful. The results of this project may influence future shoreline road infrastructure projects, however it is very important to look to the long term, and consider options for roadway relocation in order to preserve beaches and ensure that roadway infrastructure is protected from coastal hazards.
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Hanapepe Salt Ponds
The Hanapepe Salt Ponds are one of the last remaining sites for the cultivation of traditional Hawaiian salt, a practice passed down from generation to generation. Over the years, this cultural practice has been threatened by various factors including conflicting land uses, non-point source pollution and wave inundation and flooding. In recent years, the Salt Pond has experienced frequent flooding, disrupting the salt-making season for the local community.
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Public Access Inventory Update
Ensuring and providing public access to coastal resources is a key component of the Coastal Zone Management Program. The Kaua‘i County Planning Department is compiling an updated inventory of public coastal accesses and prioritizing improvements that will enhance the public's use and enjoyment of the County's shoreline.
Funding for this project was provided by OPSD-CZM pursuant to National Oceanic and Atmospheric Administration Award No. NA17NOS4190102.
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Aligning Special Management Areas (SMA) and Sea Level Rise Exposure Areas (SLR-XA)
In a proactive approach to managing coastal areas, the County Planning Department is looking to regulate more of the Sea Level Rise Exposure Area (SLR-XA). One approach is to adjust the Special Management Area (SMA) line to correspond with the SLR-XA. Currently, there are areas outside of the SMA that are vulnerable to sea level rise and erosion. The County Planning Department is working with the University of Hawaiʻi, Coastal Geology Group to develop various GIS layers to include information on: lot depth calculations, shoreline changes, the Erosion Hazard Zone with 3.2 SLR exposure areas, and the Kauaʻi SMA. This information will assist in the further understanding and regulation of vulnerable coastal areas.
Funding for this project was provided by OPSD-CZM pursuant to National Oceanic and Atmospheric Administration Award No. NA18NOS4190082.
City & County of Honolulu
Demographic Statistics:
Demographic statistics comparing Hawaiʻi State to the various counties, highlighting the City and County of Honolulu (Source: US Census Bureau).
Shoreline Characteristics Overview:
City and County of Honolulu, which is comprised of the island of Oʻahu, has roughly 180 km of shoreline, 107 km of which is sandy beach. The shoreline make-up is extremely varied in its habitat types, as well as exposure to wave energy.
The North shore (Kaʻena Point to Kahuku Point) is made up of long, sandy beaches and rocky reef points. High exposure to swells during the winter creates massive waves. However, during the summer, these same areas become flat, wide beaches with calm waters. These changing seasonal conditions result in highly variable shoreline changes throughout the year and region.
The East coast (Windward; Kahuku to Makapuʻu Point) is exposed to trade wind swells year-round. Beaches north of Kaneohe Bay are narrow with shallow fringing reefs, while beaches south of Kaneohe Bay are wide with deep fringing reefs.
The South coast (Makapuʻu Point to Kapolei) region is highly developed. It is home to the state capitol, Honolulu, as well as some of the fastest growing cities in the State. Waikīkī Beach was historically a wetland, but through extensive engineering was transformed into sandy beaches. Much of the southern coast is protected by wide, shallow fringing reefs. Towards the west, there is marsh and wetland habitat found in Pearl Harbor.
The West coast (Leeward; Kapolei to Kaʻena Point) is characterized by sandy beaches. The region has a large buffer between shoreline and development has allowed for relatively less beach loss compared to other parts of the island.
Coastal Management Challenges and Strategies:
Due to its diverse coastal habitats and shoreline uses, the City and County of Honolulu faces a variety of challenges when it comes to managing the shoreline. The County Department of Planning and Permitting, with support from OPSD-CZM, is taking steps to not only address current issues, but also proactively manage the coastline to mitigate future impacts. The map below features a select set of areas that exemplify some of the County's challenges and management strategies.
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Windward Oʻahu Roadways
Shoreline sections of the Kamehameha Highway are vulnerable to erosion and overwash during storm surges. Shoreline armoring has been used in some areas to protect from erosion, resulting in beach loss. This road serves as a main access corridor for communities in the northeastern region of the island.
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Waikiki Beaches
Due to natural processes and anthropogenic activities, Waikīkī experiences chronic beach loss. Recurring sand nourishment projects are used to maintain the beaches, which are the center of the State's tourism industry and attract over 4 million visitors per year. In some areas, seawalls were constructed in order to protect properties from erosions and wave inundation.
The continued maintenance of the beaches through renourishment projects is supported by private and public funding from government entities and community groups such as, DLNR and the Waikiki Beach Special Improvement District Association.
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Beach Nourishment at Ala Moana Regional Park
Ala Moana Regional Park is one of the State's oldest and busiest parks. It is frequented by both locals and visitors, and is host to annual events, such as the Lantern Floating Hawaiʻi ceremony and Independence Day fireworks.
In order to maintain this manufactured beach, which has no natural sand source, the County, DPR and DDC are implementing a beach nourishment project. By adding up to 70,000 cubic yards of sand to the swimming beach, this project is anticipated to restore the beach to its 1957 configuration.
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Sunset Beach
Winter wave exposure and big swells on the North Shore cause loss of sand. As the erosion worsens, it is now threatening many shoreline properties and homes.
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Shoreline and Seawall Photographic Images Database Update
This project created a series of high-resolution, digital, aerial photographs documenting the Oʻahu shoreline. These photographs are used to identify and record existing structures along the shoreline and document the condition of the shoreline as seen from the ocean.
Funding for this project was provided by OPSD-CZM pursuant to National Oceanic and Atmospheric Administration Award No. NA17NOS4190102.
Maui County
Demographic Statistics:
Demographic statistics comparing Hawaiʻi State to the various counties, highlighting Maui County (Source: US Census Bureau).
Shoreline Characteristics Overview:
Maui County is compromised of the islands of Maui, Molokaʻi, Lānaʻi, and Kahoʻolawe.
Maui Island
The island of Maui has about 193 km of shoreline, of which 90 km is sandy beach. The island regions used here, align with the Maui Island Community Plans.
The Central Maui region is composed of various shoreline types, including steep rocky volcanic coastlines, clay bluffs, sandy beach and cobble beaches. The western side is primarily volcanic soil and clay bluffs with broad fringing reefs offshore. The central isthmus, east of Kahului, is characterized by long, sandy beaches and, due to the tradewinds, a well-developed system of sand dunes. There are fringing coral reefs offshore.
The North Shore is mainly rocky headlands, cobble beaches and estuarine areas near stream mouths.
The East Maui shoreline is mostly undeveloped with steep, rocky headlands formed by geologically young lava flows. The area surrounding Hāna is characterized by pocket, black-sand beaches and shallow sloping bays. With no protecting land mass to the east, this side of the island is completely exposed to winds and waves from the north, east and south. The region west of Kaupō is almost completely undeveloped.
The South Maui shoreline is made up of long stretches of sandy beach, coastal sand dunes, and a large wetland at Kealia Pond, near Ma'alaea. While this area is relatively protected from tradewinds, it is vulnerable to erosion from large south swells.
West Maui is varied in its coastal habitats and uses. The southern end of the coast is steep and rocky, backed by steep mountains. Besides the coastal highway, there is limited development. Conversely, the northern end of the coast is highly developed and one of the major tourist centers on the island. There are many pocket beaches between Napili and Kahana, long sandy beaches at Kāʻanapali, and narrow, cobble beaches south of Lahaina. This area receives wave exposure from northwest swells in the winter, and southern swells in the summer, resulting in high seasonal variation in their sandy beaches. Due to the upper coastal plain being composed mainly of volcanic sediment, there is a limited amount of sand supply. As a result, this area experiences significant and chronic erosion damage, which has led to the construction of seawalls and other shoreline armoring projects.
Molokaʻi Island
The island of Molokaʻi has about 142 km of shoreline, and was formed by two different shield volcanoes. These two shields, which make up the eastern and western sides of the island, vary dramatically in their climates and topography.
The north coast of Central Molokaʻi is characterized by dry sandy shorelines near Moʻomomi, and rough waters and sea cliffs along the Hoʻolehua coast.
Kalaupapa Peninsula, on the North Coast, is a broad coastal plain with sandy shores on the western side and sea cliffs on the eastern side. East of the peninsula, lush, steep sea cliffs and coastal ridges and valleys extend to Hālawa. (Note: Kalawao County, which encompasses Kalaupapa Peninsula, is a non-self-governing county.)
Past Hālawa, the East End is comprised of rocky shoreline. As the coast becomes more south-facing, it transitions into sandy beaches interspersed with large sections of wetlands and mudflats. This region, has many ancient Hawaiian fishponds; however, many of them have been inundated by silt and mangroves. Offshore, a fringing reef extends for 53 km along the coast, the largest fringing reef in the main Hawaiian Islands.
Similar to the East end, the south Central Molokaʻi coast is gently sloped with shallow offshore waters. There are several fishponds and sections of wetland.
Unlike the North and East regions, West Molokaʻi is very arid. Upland erosion due to overgrazing, deforestation and invasive species has resulted in run-off and sedimentation in the southern nearshore waters. From Laʻau Point to ʻIlio Point the coast is rocky and broken up by long sections of sandy bay, such as Papohaku Beach. Around ʻIlio Point and Moʻomomi, there are large, vegetated sand dunes.
Lānaʻi Island
The island of Lānaʻi has 76 km of shoreline and is the driest of the inhabited islands. Unlike the other islands, Lānaʻi's main residential area is located in the center of the island. There is limited resort and tourism development on the southern coastline.
The North coast (Polihua to Kahokunui) is a series of sandy beaches collectively known as “Shipwreck Beach.” The region’s windy conditions have resulted in the formation of low sand dunes. There is a narrow fringing reef offshore.
The East coast (Kahokunui to Halepalaoa Beach) is north-east facing and protected from Kona storm waves. The coast is characterized by wide beaches and a wide fringing reef.
The South coast (Halepalaoa Beach to Palaoa) is characterized by wave-eroded, rocky shoreline. The Mānele-Hulopo'e Marine Life Conservation District, as well as a resort development, are located in the middle of the coastline. Continuing west along the coastline, there is a gradual transition to sea cliffs.
The West coast (Palaoa to Polihua) is characterized by steep sea cliffs, reaching up to 300m high between Kaunolu Bay and Kaumalapau Harbor. Continuing north, the sea cliffs continue and are interspersed by bays. The cliff height reduces to 100m near Nanahoa and continues to decrease as it transitions to rocky shoreline around Keanapapa Point.
Coastal Management Challenges and Strategies:
Due to its diverse coastal habitats and shoreline uses, the County of Maui faces a variety of challenges when it comes to managing the shoreline. Additionally, Maui's beaches are experiencing the highest rates of erosion for the Hawaiian Islands and 11% (about 4 miles) of beaches have already been lost. The County Planning Department, with support from OPSD-CZM, is taking steps to not only address current issues, but also proactively manage the coastline to mitigate future impacts.
The map below features a select set of areas that exemplify some of the County's challenges and management strategies.
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Sand Dune Restoration in Kihei
Due to high wave events, exposure to south swells, and intense human use, several of the beaches in the South Maui/Kihei region are vulnerable to coastal erosion. Partnerships between the Maui County Planning Department and various community groups have worked to restore dunes in an effort to proactively protect against coastal hazards.
At Charley Young Beach, a public-private partnership with community volunteers worked to restore sand dunes and remove over 150 feet of overgrown plants. The result was a doubling to tripling of the width of the beach, as well as the restoration of dunes that provide protection to vulnerable beach front homes.
At Kama'ole Beach Parks I, II and III, three ADA Dune Walkovers were designed and built via the Maui County Planning Department and University of Hawai'i Sea Grant partnerships with experts and community members. This project created designated beach access pathways in order to reduce the impact of beachgoers traversing the sand dunes.
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Addressing Coastal Erosion in West Maui
West Maui is the main tourism center for the island, and second only to Waikīkī in the state. However, the area is facing severe coastal challenges. Chronic erosion, compounded with seasonal changes in sand movement, has eroded beach areas and is threatening the structural integrity of some coastal buildings and existing sea walls.
The Maui County Planning Department and UH Sea Grant are leading three major public-private partnerships in Napili Bay, Kahana Bay and Ma'alaea Bay to implement regional beach nourishment projects. As an area with numerous stakeholders, these efforts require significant outreach and include over 40 site visits, education and outreach presentations to the public and property owners, meetings with Aha Moku Council leadership, and multiple presentations to the County Council regarding sea level rise, coastal erosion mitigation strategies and financial management of regional projects.
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Innovative Funding Tools for Shoreline Management
The Maui County Council established the Special Management Revolving Fund, which took effect in 2019. The fund is sourced from SMA permit application fees, as well as fines from SMA and shoreline violations. Funds are used to support the enforcement of SMA and shoreline rules, as well as support planning, studies and implementation of future shoreline management strategies.
The fund was advocated for by the community and models how CZM outreach and support within the community can strengthen and magnify opportunities for impact.
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Honoapi'ilani highway
This coastal highway is the main road connecting West Maui, and is vulnerable to severe erosion issues at multiple spots.
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Puamana Park
Puamana Park is a low-lying sliver park with severe coastal erosion leaving little remaining beach. The park is backed directly up to the Honoapi'ilani Highway, threatening road safety and leaving little opportunity for natural beach retreat. Additionally, the erosion of sand has exposed iwi (bones) and Native Hawaiian burial sites. The park is closed indefinitely.
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Using Shoreline Setback Rules for Proactive Management
As the administering authority of shoreline setback provisions in Maui County, the County Planning Department has established shoreline setback lines that consider erosion rates and lot depth to best protect vulnerable and sensitive areas. With the closure of the Renaissance Wailea in 2008, the property underwent a $90 million renovation to become the Andaz Resort. During the redevelopment process, hotel and county planners worked to include sea level rise planning and mitigation into the site reconstruction plans. In accordance with Maui County’s shoreline setback ordinance, the Andaz Hotel had to observe a 150 foot setback (Hawaii State Law mandates a minimum of 40 feet from shoreline to setback line, but allows counties to extend beyond state requirements (HRS § 205A-43)). By incorporating sea level rise mitigation, buildings in the 150 foot setback were demolished and relocated, thereby proactively managing for future sea level risk.
Photo 1: Andaz Resort Wailea in 2014 with buildings outside of the setback.
Photo 2: Renaissance Wailea in 2008 before renovations. Circled buildings are located within the 150 foot setback.
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Lanaʻi
The introduction of domestic and feral animals (primarily ungulates) to the island resulted in overgrazing and deforestation. The vegetation has never recovered, thereby leaving the soil destabilized and exposed. Rain events often cause considerable runoff of sediments into the coastal waters. This excess sedimentation is detrimental to marine ecosystems, especially the nearby fringing reefs, as it can block sunlight and smother corals.
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Seawall Removal at Kapalua Bay Beach
Kapalua Bay, which was awarded Dr. Leatherman's Best Beach in the USA (2018), has undergone a major improvement due to the efforts of a public-private partnership between the County of Maui Planning Department, Kapalua Resort Association and Maui Land and Pineapple Company, Inc.
Originally built in the 1970s, the seawall on the bay's southern corner, was showing signs of failure, including a sinkhole directly behind the wall, and multiple breaches in the wall itself. These were endangering public safety and environmental health.
To address these issues, the seawall and adjoining stairs were removed and the natural coastal ecosystem was restored. Additional ecosystem improvements and two new shoreline access paths were also included. University of Hawaii Sea Grant Program's dune management experts provided guidance for the project.
Photo 1: Restored coastal ecosystem at Kapalua Beach on June 2021.
Photo 2: Images of the failed seawall and sink hole.
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Maui County Shoreline Access Viewer
Ensuring and providing public access to coastal resources is a key component of the Coastal Zone Management Program. The Shoreline Access Viewer project created an interactive, online, public map identifying public sites to access beaches on Maui Island, Molokaʻi and Lānaʻi. In addition to geographic location, the resource includes information regarding lifeguard availability, parking, restroom and facilities and type of access (right of way, public park, end of street, easement). The viewer can be accessed at: Maui County Shoreline Access, HI | Official Website (mauishorelineaccess.net)
Funding for this project was provided by OPSD-CZM pursuant to National Oceanic and Atmospheric Administration Award No. NA15NOS4190105.
Hawaiʻi County
Demographic Statistics:
Demographic statistics comparing Hawaiʻi State to Hawaiʻi County (Source: US Census Bureau).
Shoreline Characteristics Overview:
Hawaiʻi County consists of the island of Hawaiʻi, also referred to as the Big Island. It is the youngest island and has three active volcanoes, which contribute to the unique coastal habitats. Volcanic activity has limited the formation of reefs and sandy calcareous beaches. There are several black and green sand beaches; however, over 75% of the 428 km coastline is made up of cliffs of varying heights. The island is separated into six main regions:
The Hāmākua Coast, which extends from Waipiʻo Valley to just north of Hilo, is characterized by dramatic sea cliffs reaching 100 to 300 ft high. It is a geologically young shoreline and there are no offshore reefs.
Hilo is one of The Big Island’s main commercial centers and Hilo Bay is one of two deep harbors on the island. There is a 3 km long breakwater that extends offshore from Kūhiō Bay. The coastline surrounding Hilo is generally rocky and irregular.
The Puna region, which encompasses the eastern most point on the island, is characterized by recent lava flows and low sea cliffs. The area has black sand beaches, as well as anchialine ponds, one of Hawaiʻi’s most unique ecosystems. Anchialine ponds are formed in young volcanic rocks and are fed freshwater from rain and groundwater, as well as ocean water from underground crevices. As a result, the ponds have a freshwater layer on top and get increasingly salty with depth. These ponds are home to many plant and animal species, including the endemic ʻōpaeʻula (Hawaiian red shrimp).
The Kaʻū region, the southern tip of the Big Island is highly irregular with a mix of black sand beaches, mauka areas of soil, and vast sections of lava. It is home to Punaluʻu Beach, a favorite lounging place for Hawaiian Sea Turtles, as well as pristine wetlands at Honuʻapo Bay.
The Kona coast extends from Manukā Park up to just south of Waikōloa Village. The southern end, near Mauna Loa, is rocky lava backed by wetland areas fed by groundwater sources. The Kealakekua Marine Life Conservation District sits midway up this region and is only accessible by boat or hiking. Moving north, the shoreline is highly irregular with sea cliffs, pocket beaches, and anchialine ponds. Offshore fringing reefs contribute to some of the island’s few white sand beaches.
The Kohala region encompasses the northern point of the Big Island. The coast is a continuation of the variation seen along the Kona coast. The Puako area is known for its tidepools and fringing reef, making it a popular scuba diving site. Kawaihae Bay is the island's second deep harbor and is fronted by reef. The leeward side of Kohala has low to moderate height sea cliffs, interspersed with pockets of boulder beaches at stream mouths. The windward side of Kohala features dramatic sea cliffs (up to 1400 ft tall), alternating with boulder and black sand beaches backed by deep valleys.
Coastal Management Challenges and Strategies:
Due to its diverse coastal habitats and shoreline uses, the County of Hawaiʻi faces a variety of challenges when it comes to managing the shoreline. The County Planning Department, with support from OPSD-CZM, is taking steps to not only address current issues, but also proactively manage the coastline to mitigate future impacts. The map below features a select set of areas that exemplify some of the County's challenges and management strategies.
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Hamakua Coast
The cliffs of the Hāmākua Coast have been experiencing erosion and collapse, posing threats to humans, property and the environment. A variety of geologic and geographic features make the cliffs unstable, such as their moist soil and clay composition, groundwater movement, and the constant undercutting of the cliffs from wave energy. Cliff failures can result in long-term environmental damage to coastal habitats. Falling debris introduces pollutants and excess sediment that can suffocate and smother shoreline and nearshore species. These cliff failures are difficult to predict and can remove 30 to 100 ft in one event.
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Hilo
Tsunamis are a relatively rare occurrence, but can have devastating outcomes. Hilo has already experienced two tsunamis (1946 and 1960) that claimed 220 lives, as well as hundreds of buildings. Areas of the city, including up to the Hilo International Airport, are designated Tsunami Evacuation Zones. OPSD-CZM has previously addressed preparedness for this coastal hazard with the production of tsunami warning signs for the County of Hawaiʻi.
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South Kohala/Puako
This low lying region is vulnerable to sea level rise and flooding. In addition to projected coastal flooding from high tides and wave encroachment, the porous geology also makes in-land areas vulnerable to flooding as groundwater levels rise and seep up to the surface. The coastal strip just south of Puako Bay is densely developed with homes on both mauka (towards the mountains) and makai (towards the sea) sides of the road.
The County Planning Department is an active member of the South Kohala Coastal Partnership (SKCP) and is committed to the implementation of the South Kohala Conservation Action Plan. One of the SKCP's projects is to develop plans for wastewater treatment facilities in order to protect coral reef health.
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Shoreline and Riparian Setback Analysis
As the youngest Hawaiian island, and with active volcanoes, the coastline of Hawaiʻi Island is unique, diverse and constantly changing. Unlike the other islands, Hawaiʻi Island does not have a comparative, foundational erosion study. To address this gap, the County Planning Department is conducting a multi-phase study of the islandʻs coastal landforms and the dynamics, resources and hazards associated with them. In 2021, the County completed Phase 1, to study historic shoreline change rates and determine typology-specific hazard assessments. Phase 1 also provided proof of concepts for Riparian Buffer delineation methods; a novel pursuit for Hawaiʻi. See second image for a diagram of the Phase 1 project workflow and derived data products.
Additional phases have expanded methodology and findings to other coastal areas in need of refined data and analysis that will inform coastal management tools for property owners.
In collaboration with PI-CASC, and with support of NOAA CZM funds, the County and the University of Hawaiʻi at Hilo, SDAV Lab use Surface from Motion (SfM) techniques to capture high resolution imagery to better study the changing coasts on the Big Island. Guided by development pressures, hazards and geological setting, additional phases produced high resolution surfaces for modeling, new coastal classifications, delineations and sea level rise inundation modeling. The results from the phased projects (1, 4, 5, 6 & 7) are being leveraged alongside a FEMA Hazard Mitigation Grant Program project (Phase 2, 3) to develop enhanced coastal setbacks and riparian buffers; coastal management tools appropriate to the hazards, landforms and development targets on Hawaii island.
In 2024, Phase 8 work will further develop cliff delineation methodologies, while Phase 9 work includes a data-driven, web-based GIS application.
Funding for these projects provided by OPSD-CZM pursuant to National Oceanic and Atmospheric Administration Award No. NA18NOS4190082 & No. NA20NOS4190042 & No. NA22NOS4190065.
5
Public Access GIS Geodatabase Pilot
Ensuring and providing public access to coastal resources is a key component of the Coastal Zone Management Program. A collaboration between the County Planning Department and the Spatial Data Analysis and Visualization (SDAV) lab at the University of Hawaiʻi at Hilo pilots an update to the regional geodatabase. If/when the project is scaled island-wide, the geodatabase will be used to support a public-facing public access map and inventory, and will enable the County Planning Department to better address statutory public access mandates.
Funding for this project was provided by OPSD-CZM pursuant to National Oceanic and Atmospheric Administration Award No. NA18NOS4190082.
Sources
University of Hawaiʻi - Mānoa, School of Ocean and Earth Science and Technology, Coastal Geology Group, 2013 ( Coastal Imagery | Hawaii Coastal Geology Group )
US Army Corps of Engineers, Hawaiian Islands National Shoreline Management Study, 2018 ( IWR Libraries (iwrlibrary.us) )
Kauaʻi Kākou, Kauai County General Plan 2018
Oʻahu General Plan 2018
Maui Island Plan 2012
Lānaʻi Community Plan 2016
Molokaʻi Community Plan 2018
County of Hawaiʻi General Plan 2005
