Hydraulic analysis for river planning is commonly conducted using the Hydrologic Engineering Center’s River Analysis System, known as HEC-RAS. This model was developed by the Hydrologic Engineering Center (HEC) of the U.S. Army Corps of Engineers (USACE). It is widely used for river hydraulic analysis, including one-dimensional steady-flow and unsteady-flow simulations.
HEC-RAS is an integrated Windows-based modeling system. It includes a graphical user interface (GUI), hydraulic analysis modules, data storage and management functions, and tools for producing tables, charts, and graphical outputs. For geometric data processing, HEC-RAS can be used together with geographic information systems (GIS) and computer-aided design and drafting (CADD) tools. This helps engineers manage complex topographic, river cross-section, and channel geometry data more efficiently.
Model results can be displayed in both static and dynamic formats. Common outputs include river cross sections, water surface profiles, stage and flow hydrographs, rating curves, and three-dimensional views of channel geometry and water levels. These outputs help engineers evaluate flood conveyance capacity, water surface elevations, and the potential effects of river improvement works.
HEC-RAS Version 6.6 was released in 2024. The software has continued to expand from traditional one-dimensional river analysis to two-dimensional flood inundation modeling, including applications using irregular computational meshes. Although two-dimensional HEC-RAS modeling is becoming increasingly important internationally, its application in Taiwan still requires continued experience, case studies, calibration, and professional review to ensure reliable results for local river conditions.