Column: Sea level rise projections are essential for proactive land use planning

This article follows recent letters to the editor and opinion pieces questioning the merits of climate science and sea level rise (SLR) projections and the need to plan for these. changes. The intention is to help clear up confusion and provide reliable information that can help inform local land use decision-making and adaptation planning based on scientific information, sound scientific resources and an unbiased assessment of current and forecast conditions.

Information is drawn from global and regional SLR projections based on rigorous, peer-reviewed scientific sources, including but not limited to the United Nations Intergovernmental Panel on Climate Change (IPCC) , the United States National Oceanographic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), and the US Geological Survey (USGS).

An important distinction is made between historical SLR rates and projected (accelerated) future SLR rates by sophisticated computer models. This critical difference in timing seems to have been missed by several recent writers of letters and opinion pieces published by the Star-Advertiser. It is not accurate or appropriate to extrapolate historical SLR rates into the future for planning purposes without also considering accelerated rates as recommended by NOAA and others, as it has been demonstrated and widely accepted in the scientific community that historical rates are expected to increase rapidly. in the future.

Sea level rise around Hawaii is expected to be higher than the global average SLR. A NOAA Mid-Sea Level Scenario predicts a local SLR of 1.16 meters (3.8 ft) by the end of the century for Hawaii. Using the Sea Level Rise Exposure Zone of 3.2 feet (SLR-XA) from the 2017 Sea Level Rise Vulnerability and Adaptation Report as a that layering of hazards is an essential first step in preparing for and adapting to the impacts of sea level rise.

Planning decisions related to critical infrastructure with a long expected life or low risk tolerance should consider higher scenarios. This aligns with Honolulu Mayor’s Directive 18-2 of 2018, which requires city departments and agencies to use the 2017 Hawaii Sea Level Rise Report and guidelines. Honolulu Climate Commission sea level rise updates of about 3.8 feet and up to 5.8 feet for planning. , scheduling and capital improvement decisions for critical projects with low risk tolerance.

Sea level rise has a direct and observed impact on Hawaii’s beaches and coastal resources. Beaches exist in a delicate balance between wave energy, sand supply and water level.

Based on studies of historic shoreline locations in aerial photographs, approximately 70% of Hawaii’s beaches experience long-term shoreline erosion due to these combined processes.

This long-term change can be difficult to achieve due to short-term changes in seasonal storms and waves. In many places, longer-term coastal erosion occurs in punctuated erosional events where the beach never fully recovers, resulting in long-term overall coastal landward movement, as seen are currently observing at Sunset Beach on the North Shore of Oahu.

Severe erosion hotspots on Oahu’s North Shore are just one of many examples of problem areas in Hawaii, including Poipu and Kapaa, Kauai, northeast Oahu, and northern and western Maui.

Avoiding these situations, and cascading impacts, in the future is mutually beneficial for owners, the community, and decision makers, and can be achieved by using future scenarios as a planning guide.

Dolan Eversole, Brad Romine and Tara Owens are part of the University of Hawaii’s Sea Grant College program.