Pre-requisite Layers and Conditions for 2D Model

To develop a GeosWMM 2D project, the following initial conditions are required:   

·       Simulated 1D Model: A simulated 1D model is required to develop 2D modeling in GeoSWMM 2D. It is a prerequisite to enable 2D flood modeling, and the 1D model must be calibrated to generate reasonable results in 2D surface flow.

·       Boundary Layer: This layer extends to the approximate boundary where the user anticipates overland flooding. Boundary layer can be represented by a polygon feature layer and can have multiple polygon features based on topographic pattern or severity of flooding. Each feature may have different 2D grid resolutions; for instance, a river and a floodplain can be represented with two different polygon features, each with different grid resolutions. Users can generate fine resolution hexagonal cell type for the river and coarse resolution hexagonal cell type for floodplain and vice versa. GeoSWMM 2D provides tools to generate boundary layer and assign attributes with ease.

·       Obstruction Layer (optional): This optional layer defines all the structures and interventions inside the watershed that will restrict water flow. Obstruction layers can include buildings, embankments, flood walls or any structure that affects the free movement of water. In GeoSWMM 2D, only polygon features can be used to introduce obstruction layers.

·       Digital Elevation Model (DEM): A DEM is a digital representation of the land surface elevation with respect to a reference datum. It is required to extract the invert elevation of 2D nodes and determine the overland flow path.