2.2.1 Inundation model

The well-known SOBEK Suite [14], developed by the Deltares Research Institute in the Netherlands, was used in the study to model flood inundation and the associated hazard. Specifically, the hydrodynamic module, which contains 1D-flow and 2D-overland flow submodules, was used to simulate surface water flow in the study area for determining the levee freeboard and inundation depth under the selected design rainfall events.

The major inputs to the SOBEK 1D/2D simulation for this study are as follows:


Figure 2. Dimensionless 24-hr design rainfall hyetograph and the downstream tide level for boundary condition [15].

elevation in 2012 was added by the cumulative land subsidence between 2012 and 2021 obtained by the land subsidence model under the conditions of with and without GWM.

4.Roughness coefficient: flow boundary roughness is categorized by the channel bed and overland surface. As almost all the drainage channels within the study area are man-made with gravel bottom and concrete siding, the nominal value of 0.02 for the Manning roughness coefficient was used according to Chow [16]. The roughness coefficient of the overland surface was determined by the land use listed in Table 2.
