Effects of Nonstationarity on Flooding of Coastal Infrastructure

Urban flooding continues to be one of the most damaging natural hazards globally. Despite efforts to mitigate flood risk, it continues to increasingly cause damage and disruption; in the US, tropical cyclones, severe storms, and inland flooding events are the first, third, and fourth most costly billion-dollar disaster events, respectively (NOAA National Centers for Environmental Information, 2022). Flood events in the US, including those caused by tropical cyclones and severe storms, cost an average of 40.6 billion USD each year and 1.7 trillion USD since 1980 (NOAA National Centers for Environmental Information, 2022). Beyond physical damages, flooding impacts local transportation networks, disrupting mobility necessary for day-to-day functions as well as for recovery.

In response, the US Department of Defense has increased efforts to evaluate and improve the resilience of the missions that are carried out at coastal military installations. Under a changing climate, many of the factors that contribute to flooding at installation locations are nonstationary in nature, such as sea level rise, river discharge trends, land subsidence, and storm severity and frequency. Hazard modeling and subsequent resilience analytics should take nonstationarity trends into account, which in turn may lead to plans and designs that deviate from historical status quo to better cope with new realities.

In this study, Adaptive Hydraulics 2D Shallow Water (AdH-SW2D), a high fidelity, finite-element model, is used to simulate hydrodynamic conditions under nonstationary conditions in sea level and river discharge over one hundred years. Two locations are identified as case studies – Camp Lejeune, NC, USA and NAS Gulfport, MS, USA. Simulations are carried out under low, intermediate, and high sea level rise for nine annual exceedance probabilities in river discharge. Maps of flood depth and extent are generated to examine the effects of nonstationarity on urban flood conditions in each location over time. Inundation conditions form the basis for various inquiries including road network connectivity, installation mission resilience, and the compounding impact of multiple threats.

Reference: NOAA National Centers for Environmental Information (NCEI) U.S. Billion-Dollar Weather and Climate Disasters (2022). https://www.ncei.noaa.gov/access/billions/, DOI: 10.25921/stkw-7w73