Inland Coastal Flooding Risk by Tropical Cyclone

Heavy and prolonged rainfall from one of the most destructive natural hazards, Tropical Cyclone (TC) generate devastating inland coastal flooding in the US. In this study, we introduce a pluvial hydrodynamic model to translate rainfall intensity of TCs as the main driver into extreme flooding hazard in coastal areas on the west side of Buzzard Bay in Massachusetts. The model implements a 2D hydraulic modeling and landscape characteristics, including geometry, land use, surface roughness, river networks, and soil infiltration. Using the continuity of mass and momentum equations, the model translates rainfall intensity of TCs that make landfall in the area into dynamic flooding during each event. The rainfall intensity data are derived from a large number of synthetic TCs (generated from historical climate through 1979-2019). The high spatial resolution rainfall intensity with short and long duration scenarios (1-hr, 2-hr, 3-hr, 6-hr, 12-hr, 24-hr, 48-hr, and 72-hr) are then used to simulate the corresponding extreme flooding during each TC. The accuracy of the developed model is evaluated by comparing flood inundation areas during observed TCs (extracted from the Synthetic-Aperture Radar (SAR) image processing) with those simulated by the model from NEXRAD data for the same events. The maximum simulated flood depth during each synthetic TC is then applied in a probabilistic framework to estimate flood levels in different return periods (up to 200 year) for each of the short and long duration scenario. The results of flood depth and inundated extent from low probable and high consequence TC floods provide critical insight for designing resilient infrastructure and reducing damages and cost against these destructive extremes. Our methodology can be applied for other susceptible coastal regions, helping identify vulnerable areas to extreme flooding induced by short and long duration TCs.