Depressed parking refers to parking with grooves in the surface. These grooves serve two purposes: first to prevent channel flow of stormwater by keeping runoff distributed across the parking lot surface and secondly to direct runoff to stormwater mitigation techniques both within and surrounding the parking area.

This strategy is by no means new and is already in place at many AF Bases; but not on parking lots. Grooved concrete was originally implemented on runways in order to improve traction for aircrafts during wet conditions. Parking lots, roads and a variety of other applications now utilize depressed or grooved parking.

Curbs are used to confine and direct runoff to stormwater management systems. Channel flow occurs as a result of curbing which in turn increases runoff velocity. High runoff velocity may cause erosion and flooding. If a depressed parking surface is implemented, the surface itself controls the direction and flow of the water.

By eliminating curbs, sheetflow created by the depressed parking will continue into adjacent Low Impact Development stormwater management measures (i.e. filter strips, rain garden etc.) at a manageable rate.

Figure 1. Open curbs for drainage at Ramstein AB

Figure 2. Typical design of a bioretention basin

Depressed parking with open curbing is a potential strategy to achieve the intent of LEED SS Credit 6.1 and SS Credit 6.2. Refer to the LEED Guidance section for specific requirements.