Managing stormwater at Pinnacle Aeropark required major drainage improvements to accommodate the park’s first development project located within a 100-year flood boundary. A hydrologic/hydraulic analysis revealed that a series of drain relocations, culvert improvements and drain cleanouts would enable the drainage system to contain the 100-year flood level impacts within a wider drain corridor. Natural stream designs were developed to relocate and widen the Blakely and Silver Drains to manage post-development flood risks.
The Blakely Drain relocation followed a Rosgen 2-stage, C-type channel design with a double trapezoid cross-section. The bottom section is used to store low flow and the upper section provides additional capacity within a 100-foot top width for high flow during wet weather. The Silver Drain used a single, 100-foot-wide trapezoid cross-section to manage high and low flows. Greater riparian environments and natural buffers were created for both drains that are expected to reduce erosion and increase nutrient removal from the stormwater. Because part of the site was located within 10,000 feet of Detroit Metropolitan Airport runways, the design was further challenged by the requirement to keep open water outside this limitation to reduce the risk of wildlife interfering with air travel.
