Note

Before you begin to create the geometric data for an HEC-RAS hydraulic model, in general you will need to create a terrain model in HEC-RAS Mapper. A terrain model is not required for 1D modeling, as the user can enter all of the cross-sectional information, structure data, etc. directly into the HEC-RAS geometric data editor. However, to perform any 2D modeling or inundation mapping, a terrain model is required. Terrain models for HEC-RAS are created using HEC-RAS Mapper. Please review how to create a terrain model in the HEC-RAS Mapper User's manual.

The basic geometric data consist of establishing the connectivity of the river system (River System Schematic); cross section data; reach lengths; energy loss coefficients (friction losses, contraction and expansion losses); stream junction information; storage areas; and 2D Flow Areas. Hydraulic structure data (bridges, culverts, spillways, weirs, etc...), which are also considered geometric data, will be described in later chapters.