Stormwater Management Case Study

STORMWATER MANAGEMENT

Defining the Problem

Stormwater runoff can be defined as “…the water that flows over the land from rainfall during or after a storm event or as a result of snowmelt” (Pyzorha 1994). Generally, part of this runoff will be absorbed through infiltration, while the rest will make its way to streams and lakes. As watersheds experience an increase in urbanization, however, impervious coverage increases, thereby reducing infiltration. Reduced infiltration increases the possibility and intensity of flooding (Booth and Jackson 1997), as well as the likelihood that runoff will become contaminated with pollutants, thereby threatening aquatic ecosystems. The relationship between watershed urbanization and aquatic ecosystem conditions

As shown in Figure 1, conveyance is a design that intends to moves water to a specific area using pipes and other impervious surfaces that do not allow infiltration. Conveyance has generally been a strategy for connecting stormwater drainage to a wastewater sewer system. This is a practice mostly taught to engineers and has been used since Romans began designing cities. In modern times, water treatment plants have been added to the system in order to remove pollutants from both stormwater and wastewater discharges. These technologies have increased the effectiveness of this technique. In fact, as stated in the Inventory, all point source discharges in Madison are directed into the Madison Metropolitan Sewerage District’s system. This has reduced the amount of pollutants being discharged into the area lakes and

Michigan State University’s Green Roof research team states, “Green roofs involve growing plants on rooftops, thus replacing the vegetated footprint that was destroyed when the building was constructed” (Michigan State University). This vegetation is most often atop a high-quality waterproof membrane that prevents leakage.

There are two main types of green roofs, extensive and intensive. Extensive roofs require no maintenance and plants must be able to survive on rainwater. Generally these roofs are inaccessible to the public. Intensive roofs are the ones that are often welcoming to people. Intensive roofs require maintenance, but also offer a more aesthetic appeal, and are most often known as roof gardens. A roof garden oftentimes includes small trees or walking paths, and therefore, is more expensive to