HEC-RAS 2D User's Manual Current: Development of a 2D or Combined 1D/2D Model PDF Download PDF Download page Development of a 2D or Combined 1D/2D Model. Current page Include child pages All pages Development of a 2D or Combined 1D/2D Model HEC-RAS can be used to develop a 2D Model or a combined 1D/2D model. This section of the manual discusses the following: Development of the 2D Computational Mesh Creating Hydraulic Property Tables for 2D Flow Areas Connecting 2D Flow Areas to 1D Hydraulic Elements Hydraulic Structures Inside of 2D Flow Areas Geospatial Coordinates for Hydraulic Outlets Connected to 2D Flow Areas Modeling Bridges Inside 2D Flow Areas Modeling Pump Stations inside 2D Flow Areas Flow Roughness Factor Curves in Calibration Regions ×