6. Shoreline Setbacks and Coastal Erosion Hazard Data
The intent of shoreline setbacks is to establish a coastal-hazard buffer zone to protect beach-front development from high-wave events and coastal erosion. Adequate setbacks allow the natural erosion and accretion cycles to occur and help maintain lateral beach access. Furthermore, setbacks provide open space for the enjoyment of the natural shoreline environment.
It is the experience of the Planning Department that the generally applied 40-foot shoreline setback was often inadequate because setbacks are not determined by historical site-specific rates of coastal erosion. Along much of the Maui coastline, this setback has failed to protect developed beach-front property from coastal erosion and has failed to provide adequate environmental open space for coastal processes. An analysis of coastal erosion trends would provide data on a property scale to enhance decision making in the coastal zone area.
Historical erosion rates can be determined on a parcel by parcel scale and used to project the future erosion hazard area along the shoreline. Maps of the projected 30-, 60-, and 90-year shorelines can be prepared assuming that future shoreline trends will be similar to historical trends. The areas makai of the projected shorelines are known as the 30-, 60-, and 90-year erosion hazard zones. Maps of erosion-hazard zones provide a scientific basis for more effectively regulating proposed structures and activities in beachfront lots.
Coastal-erosion hazard maps could be used to establish rate-based building setbacks. Setbacks would be site-specific-literally at the property scale-to reflect the site-specific nature of coastal erosion. These setbacks would also incorporate the proposed style of development. Construction-style considerations would include the size and expected lifetime of the planned structure. Larger, immovable buildings and those with lifetimes of more than 50 years would have deeper setbacks than small, movable structures. For instance, a ten-story, 200-unit condominium would have a deeper setback than a single-family house built on posts.
Establishing setbacks that reflect site-specific coastal processes and building styles could be incorporated directly into the Shoreline Setback Rules for the Maui Planning Commission along with certain construction and land-use performance standards for areas that fall within a particular erosion-hazard zone. Site-specific setbacks would also offer a basis for dune conservation.
Variable-rate setbacks may be difficult to adopt. Projected erosion rates along shorelines with a history of severe coastal erosion could significantly limit the buildable area of a beach-front parcel. The projected hazard-zone may even consume the entire property. Provisions for possible exceptions to rate-based shoreline setbacks would need to be included with any rule changes. Even if variable shoreline setbacks are not adopted by the Planning Commission, erosion-hazard maps would still provide valuable data that would be used during planning, developing, and redeveloping coastal properties. For example, erosion hazard maps could be used to identify areas prone to high rates of coastal erosion and help determine the causes of and methods to address coastal erosion.
Objectives
6.1) To provide relevant information for governmental agencies and the coastal community when purchasing shoreline property and/or planning and designing any development along the shoreline6.2) To provide a scientific basis to assess and regulate proposed structures and activities within projected shoreline erosion hazard zone
Recommendations
6.1a) Develop a detailed coastal erosion hazard analysis that will determine historical shoreline positions and map the projected position of the shoreline 30, 60, and 90 years in the future. (Maui County has already prepared and advertised an RFP to develop such a study.)6.1b) Quantify the amount of beach loss that has occurred to help identify the possible causes and potential mitigation of coastal erosion
6.2a) Incorporate site-specific erosion rate data and performance standards (e.g., construction style and estimated lifetime of structure) into the determination of shoreline building setbacks
6.2b) Initiate meetings with neighborhood associations to help develop performance standards for variable setbacks in areas with high rates of coastal erosion
|
|
|
|
|
|
|
|