Numerical simulations of three of the most severe historical tropical cyclones to affect the Delaware River Basin (DRB) are used to evaluate a new numerical approach that is a candidate model for the inland‐coastal compound flood forecast. This study includes simulating interactions of tides/surges, freshwater streamflows, winds, and atmospheric pressure for the DRB. One‐way coupling between the hydrologic (National Water Model [NWM]) and the ocean/wave (ADvanced CIRCulation model/WAVEWATCH III [ADCIRC/WW3]) models for the Delaware river‐estuarine system is developed. The links between the coastal processes and the NWM are provided by two different hydraulic and hydrodynamic models: (i) a well‐calibrated public‐domain 1D hydraulic solver model (Hydrologic Engineering Center's River Analysis System [HEC‐RAS]) and (ii) 1D/2D open‐sourced hydrodynamic model (D‐Flow Flexible Mesh [D‐Flow FM]). First, the modeling system is tested to confirm model verification and stability when the system is forced with only tidal forcing. Then, the relative performance of each modeling approach (NWM/D‐Flow FM/ADCIRC/WW3 and NWM/HEC‐RAS/ADCIRC/WW3) is evaluated using observational data from Hurricanes Isabel (2003), Irene (2011), and Sandy (2012). Furthermore, the sensitivity of water level prediction to the streamflows, different wind products, and bed roughness are examined. Results show that the D‐Flow FM is generally accurate for water levels: the water levels near the peak of the storms have a skill ranging from 0.79 to 0.91 with a negligible phase error. Simulations show that water level predictions depend on an accurate representation of the wind conditions and bottom roughness. The work shows that hydrodynamic predictions, especially upstream, are highly dependent on the streamflow discharges.

Bonnin, Geoffrey M., Kazungu Maitaria, and Michael Yekta, 2011. Trends in Rainfall Exceedances in the Observed Record in Selected Areas of the United States. Journal of the American Water Resources Association (JAWRA) 47(6): 1173–1182. DOI: 10.1111/j.1752‐1688.2011.00603.x Abstract:  Semantic differences have led to a gap in the understanding of the impacts of climate change on precipitation frequency estimates. There is popular perception that heavy rainfalls have become more frequent, and that this trend will increase with global warming. Most of the literature examines this question from the point of view of climatology using definitions of “heavy,”“very heavy,” or “extreme” rainfall, which are different from those commonly used by civil engineers. This article identifies the differences in meaning used by the climate and civil engineering communities and examines trends in the observed record in the frequency of exceedances (not trends in magnitudes). Using concepts recognized as the basis for design of the Nation’s civil infrastructure, we look at trends in the number of exceedances of thresholds for a variety of precipitation frequencies and event durations used by civil engineers. We found that the estimated trends in exceedances at one‐day and multiday durations were statistically significant and increasing for the Ohio River Basin and surrounding states but the reverse was true for the Semiarid Southwest (i.e., not significant and decreasing trends). In addition, we found the magnitude of the trends was small for all but the more frequent events and also small with respect to the uncertainty associated with the precipitation frequency estimates themselves.