Pre-requisite Layers and Conditions for 2D Model

Initial conditions to develop a GeosWMM 2D project are:

• Simulated 1D Model: A simulated 1D model is required to develop 2D modeling in GeoSWMM2D.It is a prerequisite to enable 2D flood modeling. The 1D model needs to be calibrated to generate reasonable results in 2D surface flow.

• Boundary Layer: This layer will extend to the approximate boundary at which the user anticipates surface ponding. Boundary layer can be represented by a polygon feature layer. Based on land use pattern a boundary layer can have multiple polygon features. Each feature may have different attributes. For instance, river and floodplain can be represented with two different polygon features and have different attributes. User can generate fine resolution hexagonal cell type for the river and coarse resolution hexagonal cell type for floodplain. GeoSWMM 2D provides tool to generate boundary layer and assign attribute with ease.

• Obstruction Layer: This layer defines all the structures and interventions inside the watershed that will restrict the water flow. It is an optional layer. Obstruction layer can be buildings, embankments, flood wall or any structure that affects the freely moving water flow. In GeoSWMM, 2D only polygon features can be used to introduce obstruction layers.

• Digital Elevation Model: Digital Elevation Model (DEM) is the digital representation of the land surface elevation with respect to any reference datum. It is required to extract the invert elevation of 2D nodes and determine the overland flow path. Only .tiff format is allowed as the DEM layer.