right|300px|thumb|1D HEC-RAS model, showing river line and cross-sections. Each cross-section is depth-averaged.
right|300px|thumb|1D HEC-RAS model, showing river line and cross-sections. Each cross-section is depth-averaged.
HEC-RAS (short for Hydrologic Engineering Center River Analysis Software) is a simulation software used to model the hydraulics of water flow through natural rivers and other open channels. The program was developed by the United States Army Corps of Engineers (USACE) at the Hydrologic Engineering Center (HEC) in Davis, California as a successor to their HEC-2 Water Surface Profiles program. HEC-RAS version 1.0 was released in July 1995, with the capability to model steady flow in one dimension; since then, further releases have increased the modeling capabilities to include quasi-unsteady and unsteady flow, two dimensional modeling, sediment transport and water quality modeling, and distributed hydrologic modeling (Rain-on-Grid.) The program is free to download from HEC, though there is no support provided for non-USACE users.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).