Document Model

Last updated: 2026  ·  US Army Corps of Engineers

Every HEC-RAS project is organized around a document model — a hierarchy of data objects that together define a hydraulic simulation. At the top sits a Plan, which references the geometry, boundary conditions, and computational settings needed for a single model run.

Key Objects

• Plan — top-level container linking geometry, boundary conditions, and run settings (time window, computation interval, equation set).
• Geometry — the physical model: 2D flow areas, computational mesh, breaklines, and connections to terrain and roughness layers.
• Boundary Condition — time-varying hydraulic inputs (flow hydrographs, stage hydrographs, normal depth) that drive the simulation for a specific event.
• Terrain — digital elevation model (DEM) that defines land surface elevations for the 2D flow area.
• N-Values — Manning's roughness coefficients assigned spatially via land-use polygons or uniform values.
• Classification — discrete land surface property layers (land use, soil type) used for roughness mapping and infiltration parameters.

Interactive Diagram

The diagram below shows the relationships between the core document model objects. Click any node to zoom in and view its properties. Click Back to return to the full diagram.

Entrance — Nodes fade in by tier, edges draw in.  Click — Zoom into node detail view.  Back — Return to full diagram.