Development and Validation of Accumulation Term (Distributed and/or Point Source) in a Finite Element Hydrodynamic Model

During tropical storms, precipitation and associated rainfall-runoff can lead to significant flooding, in both the upland and coastal areas. Flooding in coastal areas is compounded by the storm surge. Several hurricanes in recent history have exhibited the destructive force of compound flooding due to precipitation, rainfall-runoff, storm surge and waves. In previous work, various coupled modeling systems have been developed to model total water levels (defined as tides, waves, surge, and rainfall-runoff) for tropical storms. The existing coupled system utilizes a hydrologic model in the upland areas of the domain to capture the precipitation and rainfall-runoff associated with the storms; however, in the coastal areas the precipitation and rainfall-runoff is not captured. Herein a source/sink term is incorporated within the hydrodynamic model itself to capture precipitation and rainfall-runoff over the already inundated coastal areas. The new algorithm is verified for several idealized test cases, and then it is applied to Hurricane Irene. Validation indicates that the new methodology is comparable to the existing river flux forcing under most conditions and allows for the addition of streamflows due to overland runoff, as well as the actual precipitation itself.