Watershed Hydrology/River Hydraulics

The Rouge Project developed a continuous, growing-season model of the entire watershed and the major river branches using the USEPA Storm Water Management Model (SWMM). The model is used as the hydraulic driver for the riverine water quality model. It has also been used to assess river hydraulic impacts for issues which arise in the subwatershed planning efforts. Questions it has addressed include:

• How will expected land use changes impact instream hydraulics (flow rates, volumes, depths and velocities)?
• How will proposed CSO control facilities impact instream hydraulics?
• What combination of storm water BMPs and CSO controls will reduce instream peak flow rates to within desired target regimes for suitable fish habitat?

The SWMM RUNOFF block is used to model the hydrology of all storm sewered areas and areas with natural drainage. An existing SWMM RUNOFF/TRANSPORT model, the Greater Detroit Regional Sewer System Model is used to model all CSOs entering the river. Inflow hydrographs from both these models comprise all inputs to the one-dimensional river model, which is simulated with the SWMM TRANSPORT block. A continuous simulation with the full model was calibrated to 6 months of 15-minute data collected with a network of rain and stream flow gages.

The SWMM hydrology/hydraulics model was used to evaluate alternatives in the same three detailed subwatershed studies referenced above for the WMM model. The detailed results are in the following reports: Middle 1 Subwatershed SWMM Modeling for Subwatershed Management Plan Development; Middle 3 Subwatershed SWMM Modeling for Subwatershed Management Plan Development; and Upper 2 Subwatershed SWMM Modeling for Subwatershed Management Plan. As an example, for the Upper 2 Subwatershed Management Study, the model was used to evaluate several scenarios including the cumulative impact of future land use projections, complete CSO control, and placement of regional extended dry detention ponds throughout the subwatershed. A fourth scenario involved placement of such ponds at only a few select locations in the subwatershed instead of everywhere. The results were used to show that existing high flow rates and velocities and the resultant bank erosion problems will worsen with future development, however, regional detention could be used to accommodate future land use changes and reduce peak stream flows and velocities below existing conditions.

Please address all comments and suggestions about the contents of this Web page to rougeweb@co.wayne.mi.us.

The Rouge River National Wet Weather Demonstration Project is funded, in part, by the United States Environmental Protection Agency (EPA) Grants #XP995743-01, -02, -03, -04, -05, -06, -08 and C-264000-01.