Incorporating Sea Level Rise Data into Hazard Mitigation Maps for New Jersey Municipalities
Ocean County, New Jersey, was heavily impacted by Hurricane Sandy. As a result, the 33 municipalities in the county sought more information to plan for current and future flood risks. When it came time to develop its first hazard mitigation plan, county officials wanted to make sure climate change was included as a profiled hazard, and be the first to include a sea level rise risk assessment.
Local community members and government officials came together to discuss how they could better prepare for and mitigate hazards, especially flooding related events. They decided that identifying areas of future inundation caused by increases in sea level was a top priority. First, geospatial data layers that identified areas inundated by 1 foot and 3 feet of sea level rise above mean higher high water (MHHW) were obtained from the Digital Coast Sea Level Rise and Coastal Flooding Impacts Viewer. The team then produced community-scale maps that combined these areas of anticipated inundation with local critical facility information such as hospitals, fire departments, and schools. In addition, the total area exposed to permanent inundation was provided for each community.
The hazard mitigation plan and sea level rise mapping provided Ocean County communities with critical information to plan for current and future flood risks. Municipalities selected mitigation actions that would address the combination of coastal erosion, floods, hurricanes, nor’easters, tropical storms, and climate change. An example of a new mitigation action involves increased “freeboard,” the term used to describe the required elevation of a structure above the FEMA-identified base flood elevation. New Jersey requires one foot of freeboard, but increasing numbers of municipalities, such as Mantoloking and Tuckerton, now require two to three feet of freeboard to better prepare for future sea level rise and coastal inundation. Sea level rise mapping also provides information to municipalities as they plan to mitigate and improve critical facilities vulnerable to inundation.