- Coastal erosion hazards on the Island of Maui can be divided into two
general categories. Chronic shoreline retreat results from the gradual narrowing of
beaches and shorelines over time under the influence of long-term dominant coastal
processes and features of the littoral sediment budget that cause local sediment
deficiencies. Episodic shoreline retreat results from large episodic erosion events
such as Kona storms, hurricanes, and large seasonal swell, and is typified by rapid
recovery of the shoreline to its original position.
Previous studies of coastal erosion on Maui have focused on chronic
erosion, providing projections of future shoreline position based on extrapolation of
historical erosion data. These studies, while helpful in predicting the long-term
position and future behavior of the shoreline, lack a careful consideration of
episodic erosion hazards and do not specifically address the dynamic nature of
Maui's coastline. It is this dynamic shoreline behavior that often constitutes the
most severe coastal erosion hazard at many locations on Maui, and is often not
represented in long-term average erosion rate analyses. This study builds upon
previous studies, analyzing existing, raw shoreline position data to quantify the
dynamic nature of Maui's coastline.
This report also provides a quantitative assessment of current shoreline
setback policy based upon these historical shoreline variability data. Coastal
development on Maui is currently prohibited between the shoreline, defined as the
highest annual reach of the wash of waves, and a shoreline setback line, located at a
distance from the shoreline that varies according to lot size. Existing shoreline
setback regulations do not take into consideration the history of shoreline
variability at particular locations, and as a result, have often failed to protect coastal
development and public resources from the effects of coastal erosion. This failure
has been widely reported elsewhere, but to date has not been quantified.
Finally, recommendations for changes to Maui's current shoreline setback
regulations to better incorporate data from the above analyses are presented.
Regulatory changes that further limit the range of permitted uses of coastal
property raise significant legal issues. Central to the discussion are the principles of
the public trust doctrine and the provisions of the U.S. Constitution's Fifth
Amendment prohibition of governmental takings without just compensation. An
overview of these issues is presented, including a discussion of several key features
specific to the public trust doctrine in Hawaii and several unique characteristics of
Hawaii's coastal zone management regulatory framework that play a key role in
how these policies affect the feasibility of new shoreline setback regulations. A
model shoreline setback ordinance for Maui County that incorporates the issues
discussed in this report is presented.