Evaluating Hydrologic Trends at Coastal DoD Installations

Installations across the Department of Defense (DoD) are located along the coasts of the United States. These military installations are exposed to numerous threats, including a changing climate, which impacts the frequency of extreme weather events, creates long-term changes in the environment, and alters the risk of nuisance or recurrent flooding to built infrastructure. In the last 30 years, 88 tropical cyclones of varying intensities have passed within 25 km of these installations, exposing the DoD to significant hydrologic threats. The four hydrologic components of recurrent flooding are sea-level rise, tidal fluctuations, storm surges, and changes in rainfall event intensity. These individual events, however, do not occur in isolation. Instead, combinations of these events exacerbate the extent of the damages and create compound resilience challenges. Coastal installations are experiencing higher magnitude and frequency of such events due to climate change and are result in annual disaster costs of $20-30 billion per year by the end of the century. This study investigate historical precipitation and tidal data for long-term temporal trends (1985 to present) using both peak and threshold exceedance frequencies as flood-risk indicators to identify temporal trends in these hydrologic components. Initial results indicate varying changes in hydrologic threats across the East and Gulf Coasts for 20 U.S. Air Force installations. The trendline results are mapped and then undergo a k-means clustering analysis to determine where significant spatial relationships of climate change-driven nuisance flooding exist to inform regionally focused policy for climate change adaptation within the DoD.