Institute for Water Resources

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Posted 10/31/2018

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ALEXANDRIA, VIRGINIA.   The U.S. Army Corps of Engineers (USACE) Institute for Water Resources (IWR) recently released its “Hawaiian Islands Regional Assessment National Shoreline Management Study” report. This report provides an assessment of the effects of erosion and accretion upon socio-economics and the environment, and what management actions are being taken or are needed to maintain resilient shorelines.

The National Shoreline Management Study

The Congressionally authorized National Shoreline Management Study (NSMS) is the first undertaking in nearly a half century to document the physical, economic, environmental, and social impacts of shoreline change across each region of the U.S.  The NSMS provides government policymakers, coastal engineers and scientists, and stakeholders with information about the coastal regions most in need of resilience planning.

The Hawaiian Islands Regional Assessment

Most of Hawaii’s beaches and shorelines are eroding, threatening the economy, environmental resources, and infrastructure. A 2012 assessment found that over the last century, 70 percent of the beaches were eroding on Kauai, Oahu, and Maui and that 13 miles of beaches had been lost. 

Beaches are the lifeline of Hawaii’s economy and a major contributor to the national economy. Tourism and recreation in the Hawaiian Islands rely heavily on sandy beaches and clean water, drawing visitors from the U.S. mainland but also from the Pacific Rim countries. Sandy beaches are also an important part of Hawaii’s culture and heritage. The ocean-based economy and shoreline resources of Hawaii are worth upwards of $9 billion annually. Shoreline erosion and associated beach loss have the potential for substantial negative impacts to the economy, the high quality of life residents and visitors enjoy, cultural resources, and coastal ecosystems.

Coastal habitats and water quality are critical to the natural environment, society, and the economy of Hawaii. Hawaii’s reefs are particularly important habitat as they provide the critical first line of defense against wave-driven coastal erosion by absorbing wave energy. Preserving Hawaii’s reefs is key to coastal protection and should be approached in a holistic fashion, linking the activities in the islands’ watersheds and near shore waters to potential impacts to the reefs.

Climate change and sea level change are compounding the challenges of, and need for, effective beach and shoreline management. The State of Hawaii, led by the Department of Land and Natural Resources, is investigating impacts of sea level rise on increased coastal erosion and inundation through a statewide Sea Level Rise Vulnerability and Adaptation Report required by the Hawaii Climate Adaptation Initiative (State Act 83, 2014).

Historically, government agencies approved and permitted seawalls, revetments, and other coastal armoring structures to defend against erosion. In addition, there are many unpermitted structures from past decades on the shoreline.  Over the last two decades, the science and understanding of the impacts of coastal armoring has increased, and we now know that in many cases, shoreline hardening can increase erosion of adjacent shorelines. In more recent times, “soft” erosion control measures, including beach nourishment, have been utilized.  Managed retreat of shorelines and erosion-based building setbacks (e.g., Kauai or Maui) have proven sustainable long-term strategies for shoreline management, but retreat is more difficult to implement where shorelines are already developed. 

This NSMS report on the Hawaiian Islands is a positive step in the direction towards a comprehensive assessment and development of plans for actions that build resiliency into state coastal economic development and environmental programs. 

Learn More

For more information, visit

Download the Report