A few years ago, Prein&Newhof helped Plainfield Township, Alpine Township and the Kent County Drain Commissioner address a serious flooding problem at York Creek along Four Mile Road. In general, pervious areas were declining in the watershed. York Creek’s flow is very flashy (responds very quickly to rainfall) because it drains a large, densely developed and steep area. Three residential homes and several downstream structures flooded frequently.
Prein&Newhof obtained a FEMA grant on behalf of the Kent County Drain Commissioner to buy and clear houses from this flood-prone area, and converted the vacant land into a side-stream detention area. When flow in York Creek rises during an intense storm, it spills out of its banks–on purpose–and floods the side-stream detention area until flow in York Creek subsides. This has the effect of reducing the peak flow in York Creek, which reduces downstream flooding. Downstream property owners have confirmed the significant impact of the project.
This video shows our design at work during a recent intense rainfall:
Our design team used the SWMM and HEC-RAS hydraulic models to evaluate the impact the new design would have on peak flows and flood levels downstream. A cost-benefit analysis indicated that the reduced flooding frequency by adding the proposed detention area was enough to justify the FEMA Grant for $430,000.