NHC has been designing steep streams for over a decade and developed an internal tool owned by NHC from 2010 to present. Prior to the initiation of the WSDOT-funded Steep Channel Design Methodology work in 2024, the tool pre-existed in the form of an excel macro-enabled software tool.

The tool was refined and improved as part of conducting the Steep Channel Design Methodology scope of work for WSDOT and released as part of the Draft 2025 State of Practice Report (NHC, 2026) and, under the Architectural & Engineering Services Agreement Number Y-13058 and Professional Services Master Agreement Y-12527, that version of the tool became the property of WSDOT.

The "Steep Channel Toolbox" web application was developed in January 2026. The current web-based tool uses the same principles of analysis as the WSDOT macro tool, and has refined the model output and user interface.

The current application and all previous versions of the tool provide a scientific application used to assist in the design of steep channel streams, and it is not an engineering tool intended for stand-alone channel design. The calculated results may include errors or omissions and should not be relied upon solely for engineering design. Design engineers are responsible for developing an appropriate means of checking and verifying the validity of calculated results and output from the tool.