Real Time Flood Forecasting in Estuaries: Integrating riverine flows, tides and storm surge

Flood hazards are costly natural hazards and account for major losses such as lives and property destruction. An accurate prediction of river-estuary-coastal flooding is essential for a cost effective storm mitigation, emergency management plans, flood insurance and planning. The recent hurricane seasons demonstrated the importance of integrating riverine and coastal model forecasts for total water prediction in estuarine areas. This can be exemplified in the unprecedented damage recorded in North Carolina in 2016. The current challenge encompasses integrating the complex dynamics of local wind effects, riverine flows, storm surges and tidal oscillations to develop a tool capable of integrating all the governing phenomena and predicting the total water levels in estuaries. This study presents the influence of local wind effects and riverine flows onto a coastal flood forecast system for the Chesapeake Bay estuary. During the modeling, it was found that the water levels increased by 3 feet on average above the normal tides along the Potomac River, with the local winds blowing at more than 15 m/s (impact winds). Likewise, when investigating the effect of river inflows, the rainfall induced higher riverine flows from Little Falls and Bladensburg into the Potomac River. This accounted for an increase of water levels by 2-3 feet at the confluence point. Thus, multi-model automated flood forecast approach takes a closer account of the riverine flows and local winds to make precise flood predictions. The iFlood Chesapeake Bay Forecast System (iCBFS) is utilizing Advanced Circulation coastal model (ADCIRC) forced by wind and pressure from the North American Mesoscale Model (NAM-12km) to predict water levels up to 3.5 days in the future. In addition, it is competing with the operational forecast systems of National Oceanic and Atmospheric Agency (NOAA) at a skill of 0.85. Additionally, in a coupled modeling framework, the Potomac forecast system utilizes the forecasts from the iCBFS with the integration of riverine flows from 1-D model (HEC-RAS) and River Forecast Center (RFS), in order to provide comprehensive water predictions in the National Capital Region. As a result, the forecast skill of the integrated system is found be significantly higher than the single coastal model approach.