HEC-RAS 2D - an Accessible and Capable Modelling Tool

Creating 1D/2D hydraulic models to assess waterway design and flood impacts can be a time consuming and expensive task. Two key factors that can determine the cost of developing a hydraulic model for a project are model build time and software licensing costs. Using the free and intuitive HEC-RAS 2D software, we are now able to reduce modelling costs, making modelling a more attractive option for clients and modelers. This will enhance the accessibility of 2D hydraulic modelling in the consulting industry.

This paper focuses on how the capabilities of the recently released HEC-RAS 2D have been applied successfully to assess flood risk at a highway bridge and evaluate initial design options for flood risk mitigation. Use of HEC-RAS 2D in testing and refining of stormwater culvert design options is presented as a second application. The paper also highlights some of the challenges and limitations of the software.

The Matekerepu Bridge modelling project is an example where HEC-RAS 2D has been used with success. A combination of 1D/2D hydraulic models was required to test existing flood risk and then assess multiple initial design scenarios. The decision was made to invest time and resources into learning and using HEC-RAS 2D instead of other commercially available packages.

Another example of the use of HEC-RAS 2D is the cross-drainage design of the Hamilton Section of the Waikato Expressway. In this project, HEC-RAS 1D/2D coupled models were built to test and verify different design options for several stormwater culverts, and to compare flood levels before and after construction to address consent requirements.

The use of HEC-RAS 2D in the above projects provided us an opportunity to deliver a final product that was robust and cost effective. The case studies should guide others in using the software, and having confidence in the results.