This document is a supplement to the Hawaiʻi Sea Level Rise Vulnerability and Adaptation Report (“Report”; Hawaiʻi Climate Change Mitigation and Adaptation Commission, 2017) and the Hawaiʻi Sea Level Rise Viewer (“Viewer”) (both available at climate.hawaii.gov). The primary purpose of this document is to assist state and county planners, natural resource and infrastructure managers, and others with understanding and using the Sea Level Rise Exposure Area (SLR-XA) from the Report and Viewer in day to day planning and permitting decisions, particularly at the project or property-level scale (Figure 1). This guidance was developed in response to requests from county planning departments and other stakeholders to provide information on appropriately interpreting and applying the SLR-XA map data in land use planning and permitting decisions while understanding the methods, assumptions, and limitations of the data.
The SLR-XA is the combined projected footprint of three chronic flooding hazards with sea level rise: passive flooding, annual high-wave flooding, and coastal erosion. Following initial inquiries from county agencies, a working group of county and state agency representatives and subject matter experts was convened in 2019 to discuss challenges with and opportunities for applying the SLR-XA map data and its three constituent hazard models at the property scale. This guidance is intended to address the following needs and challenges posed by the working group and others:
• Incorporating the SLR-XA in land use plans and policies;
• Interpreting and applying the spatially-variable SLR-XA data;
• Applying the SLR-XA in permit review at the property scale; and
• Relating the SLR-XA model projections to existing shoreline hardening and backshore geology.