Overview

HEC-RAS (River Analysis System) is a software application designed to perform one-dimensional and two-dimensional hydraulic modeling of rivers, streams, floodplains, and other open channel systems. HEC-RAS is widely used by engineers, planners, and regulators worldwide. It is considered an industry standard for hydraulic modeling and plays a critical role in floodplain mapping, permitting, and emergency management efforts.

Key Features:

  • 1D and 2D Flow Modeling: Simulates steady and unsteady flow in rivers and channels.
  • Floodplain Mapping: Generates flood inundation maps and depth grids for risk analysis and communication.
  • Sediment Transport and Water Quality: Models sediment movement and basic water quality parameters.
  • Bridge and Culvert Analysis: Evaluates hydraulic impacts of bridges, culverts, and other structures.
  • Dam Break and Levee Breach Analysis: Assesses consequences of structural failures and emergency conditions.
  • Integration with GIS: Works with tools like RAS Mapper for spatial data analysis and visualization.

Accomplishments

Bug Fixes and Testing in CWMS 3.5

In FY25, the team focused on stabilizing the HEC-RAS 6.x line and delivering fixes that directly benefit CWMS users. Key changes include:

  • Bridges (1D) – Improved momentum method for steep slopes and rapidly changing cross sections, resulting in more stable, physically consistent simulations.
  • Lateral Structures – Fixed an issue in HEC-RAS 6.6 and early 6.7 beta builds where structures could become uncoupled from their tailwater connection. Structures now remain correctly linked to downstream elements.
  • Bridges (2D) – Updated the 2D bridge approach so energy losses are applied at the bridge faces under the deck, improving realism for head loss through the opening.
  • 2D Connections – Weir flow now offers an option to use the Energy Grade Line as the headwater reference.

The team also completed integration testing of HEC-RAS 6.6 within CWMS 3.5. All issues found were logged and addressed to ensure that the current builds perform as expected.

Participate in CWMS NIP Monthly Working Sessions

The MMC hosts monthly working sessions on Microsoft Teams, providing HEC-RAS modelers with access to expert support. The team participated in these sessions during FY25, as they have been highly valuable to users. These meetings are an effective platform for delivering field support, answering questions, and demonstrating key software features.

Provide Field Support

The team provided approximately 140 hours of support in FY25 to assist field staff in using HEC-RAS in CWMS.

Develop New Tutorials

The development of new tutorials was deferred in FY25. Plans to develop new tutorials will continue into FY26.

Plan for Integration of RAS 2025 in the CAVI

A meeting was held in May 2025 to develop a plan for integrating RAS 2025 into the CAVI. During the meeting, it was decided to postpone integration planning until RAS 2025 includes additional features required for forecast modeling within CWMS.