Featured Projects — Software HEC-RAS2D

The Hydrologic Engineering Center’s River Analysis System (HEC-RAS) is a software product used to perform free-surface hydraulic calculations for overland flow. Historically, HEC-RAS was born as a product for 1D networks of open channels and rivers. In 2011, HEC asked RMA to develop an extension of HEC-RAS for 2D flow. Since then, RMA has been the developer behind the 2D computational engine, a fundamental part of HEC-RAS starting with version 4.2 (2014).

RMA has implemented two theoretical models for solution of 2D flow:

  • Shallow Water Equations Solver, which disregards vertical velocities and assumes hydrostatic pressure
  • Diffusive Wave Approximation Solver, which additionally omits unsteady, advection and turbulent viscous terms, providing a model with a narrower range of applicability but many computational advantages

The RAS2D solvers developed by RMA have multiple features that distinguish them from comparable software products

  • Application to a wide variety of computational grids independently of their structure and orthogonality properties
  • Bathymetric information and geometric aspects that allow coarser grids and improve computation speed
  • Effortless application of various boundary conditions and seamless integration into the 1D HEC-RAS software
  • Stable and efficient treatment of wetting and drying
  • Fully multi-threaded execution easily controlled by the user

Results and benefits

The 2D computational flow solver within HEC-RAS is the primary tool to perform free-surface hydrodynamic analysis for dam breaks, levee breaches, and flood scenarios. Our scientific software development has expanded the range of applicability of HEC-RAS and solidified its position as one of the main products for hydraulic simulation.

Screenshot of colorful model showing flooded city.

Urban levee breach simulation (Saint Paul, MN).

Screenshot of models showing high volume water flow.

Left: Rainfall simulation for watershed overland routing. Right: Flood wave propagation down a river valley following a dam failure.