ASSESSMENT OF INUNDATION RISK FROM SEA LEVEL RISE AND STORM SURGE IN COASTAL NATIONAL PARKS

Abstract

In coastal ecosystems, sea level rise and an increase in storm frequency and intensity are two major impacts expected to result from climate change. Coastal National Parks have many low-lying areas that are at risk from inundation resulting from these impacts. In order to help park managers meet their goal of preserving valuable resources, I developed a methodology to evaluate risk of inundation from sea level rise and storm surge at sentinel sites, areas of importance for natural, cultural and infrastructural resources. I performed a literature review on the factors driving sea level rise in the Northeast, and conducted an evaluation of the methods used by scientists and engineers to model sea level rise and storm surge inundation. I selected the most recent and appropriate geospatial tools, models and datasets to perform a coastal inundation risk assessment in three northeastern coastal National Parks—Boston Harbor Islands National Recreation Area, Cape Cod National Seashore, and Assateague Island National Seashore. I collected elevation data at sentinel sites using real time kinematic global positioning system (RTK GPS) technology and assessed the accuracy of the most recent, readily-available Light Detection and Ranging (LiDAR) derived Digital Elevation Models. Because of the poor quality of existing LiDAR data, Boston Harbor Islands National Recreation Area was excluded from the final assessment. I evaluated risk of inundation at sentinel sites in Cape Cod and Assateague Island using three modeling approaches: bath-tub modeling, Sea Level Affecting Marshes Model (SLAMM), and Sea, Land and Overland Surges from Hurricanes (SLOSH) Model, and developed an overall inundation index, a single measure of inundation likelihood that incorporated output from each modeling approach. I created inundation maps for a range of sea level rise and storm surge scenarios, calculated the probability of inundation at each sentinel site given the uncertainty associated with each model and dataset, and ranked the relative risk of sentinel sites to inform management and adaptation strategies. Cape Cod’s sentinel sites, which in many cases occurred in high elevation settings, were found to be less vulnerable to inundation than Assateague Island’s sentinel sites which were distributed in low-lying areas along the barrier beach island. This inundation risk assessment methodology can be applied to other coastal parks and to the same coastal parks at different times as more accurate elevation datasets and updated sea level rise projections become available.