Allow for hydraulic computations to use the peak flow from hydrographs and instead of the dynamic flows generated from the hydrographs. The software StormShed (which is an allowed software for design use by WSDOT) calculates the peak flow from the SBUH, then all the calculated peak flows form the catchment areas are used for design. So, if we have a run of inlets in a pipe network, the hydrograph peak flow from each catchment area going to an inlet is added up as the pipe network drains downstream.

This is different from OpenFlows where the dynamic flow at each timestep is calculated and the maximum flow at a pipe may not necessarily be equal to the sum of all peak flows from the contributing catchment hydrographs, depending on catchment time of concentration and flow time in the pipe network.

Being able to do this type of calculation would make getting approval for using the Bentley OpenFlows software on WSDOT projects easier since we can easily demonstrate that the software is similar to StormShed and produces equal results. Currently the workaround is calculate the hydrograph peak flows for all catchment areas. Then having to switch to a "rational computation" model and take all those peak flows and "inject" the flows into the network as fixed flows at all inlets. However, this gets complicated when ditches are involved in the design process.