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Sea Level Rise

Exterior view of a flooded neighborhood
Source: NOAA

According to the Intergovernmental Panel on Climate Change 5th Assessment Report, released in September 2013, global average sea level is projected to rise by 10-39 inches by the year 2100 (relative to mean sea level from 1985 to 2005), depending on the atmospheric carbon emissions scenario assumed. This projection is considered to be based on the best available science in the “Sea Level Rise Policy Guidance” document adopted by the California Coastal Commission in August 2015. These projections are likely to change over time as climate science progresses.

Perhaps the most obvious and widespread consequence of sea level rise is inundation and flooding of land. Sea level rise will not only cause permanent land inundation near coastlines, it will increase and expand the 100-year floodplain in coastal communities. Thus, the number of residents at risk during storm events would increase. Shorefront land composed of fill is at risk for inundation because of low elevation and subsidence over time due to compaction from buildings and soil desiccation. Additionally, shoreline dikes and sea walls likewise may be at risk for overtopping and inundation. The National Oceanographic and Atmospheric Administration (NOAA) provides an online mapping tool that illustrates the scale of potential flooding along the coterminous U.S. coast assuming various sea-level rise scenarios (visit: https://coast.noaa.gov/slr/ ).

California law does not currently mandate disclosure of sea level rise in real estate transactions. However, in 2015 the state began updating its General Plan Guidelines for cities and counties to include land-use planning to avoid sea level rise hazards within their municipal jurisdictions. In addition, many coastal cities and counties are independently addressing global sea level rise by adopting land-use policies that anticipate rising sea level.

Increasingly, these local policies result in sea-level rise inundation zones on maps in the municipality’s General Plan Safety Element, and those zones guide building departments in the permit approval process. Hence, a prospective buyer may consider it to be material if the sale property is located in such a locally designated hazard zone. (Source: NOAA, California Coastal Commission, California Governor’s Office of Planning & Research)