Development and application of a continental scale compound flood
modeling system in a complex coastal flood plains
Abstract
We present a high-resolution continental-scale compound flood modeling
system. It aims to quantify inland flooding resulting from the composite
effects of riverine discharge and surface runoff and storm surge, in the
inland-coastal zone during significant riverine and coastal storm
events. This is achieved by coupling three continental models: the
National Water Model (NWM) for the hydrology component, the Advanced
Circulation Ocean Model for the coastal storm surge component, and the
WAVEWATCH III model for the surface wave component with a detailed
inland-coastal inundation model as the mediator between coastal and
inland hydrology module. The inundation model, Delft3D FM, D-Flow
Flexible Mesh (D-Flow FM), uses a high quality 2D unstructured grid with
high-resolution (~100 m) near coastal features and
lower-resolution in other areas to resolve the geometry of the study
area. The coastal features are collected from NWM streamlines, National
Hydrography Dataset, US medium shorelines and bathymetric features from
the United States Army Corps of Engineers . The D-Flow FM model is
forced by time-varying water levels and riverine discharges applied at
its offshore and inland boundaries, respectively, by spatially- and
time-varying wind and pressure fields and incorporates the contributions
of surface and subsurface runoff to the total discharge in rivers,
channels and streams. We conducted model validations for the following
four major flooding events across the US coast: Hurricanes Ike (2008),
Sandy (2012), Irma (2017), and Florence (2018). The results highlight
the importance of including composite effects of compound flooding to
accurately predict water levels during combined river flooding and
extreme storm surge events.