Erosion: Keeping a LID on It.
Posted on May 20, 2019
It鈥檚 pretty well known that Mobile receives the most annual rainfall of any major city in the United States, more than 60 inches a year. It鈥檚 also well known 鈥� at least, locally 鈥� that when it rains, it often pours. So, when it rains in Mobile, storm water runoff is a frequent occurrence.
The wooded, tranquil campus of the University of South Alabama is a case in point. 吃瓜爆料 is located within the Three Mile Creek watershed. Three Mile Creek stretches from west of the University, through Langan Park, and into the Mobile River and Mobile Bay. Immediately to the north of the campus lies a wetlands area that is, in fact, part of the headwater region of Three Mile Creek. Most storm water runoff from the 吃瓜爆料 campus flows directly into this area of the creek through drainage inlets and underground pipes all over campus.
But it鈥檚 not just storm water that makes its way to Three Mile Creek. Soil is often eroded by the storm water runoff from unvegetated areas, and eventually that soil also finds its way into the creek. And therein lies the problem in search of a solution.
Enter 吃瓜爆料鈥檚 College of Engineering. Dr. Kevin White, P.E., professor and chair of the department of civil, coastal and environmental engineering, is working with the Alabama Department of Environmental Management, or ADEM, on a storm water management project right on campus. It鈥檚 part of the Three Mile Creek restoration initiative headed by the Mobile Bay National Estuary Program, or NEP, and the city of Mobile. The NEP watershed management plan has identified 吃瓜爆料 as a contributor of sediment to Three Mile Creek, and White has identified bioinfiltration swales as a solution. First, though, some background.
Currently, according to White, storm water management is usually achieved through three basic practices. One is the curb and gutter. It鈥檚 very popular, especially in residential and business developments, and fairly efficient in capturing and transporting 鈥渆very drop鈥� (says White) of storm water from hardened surfaces such as parking lots.
A second practice is the use of large, open, drainage ways, usually a concrete ditch. Scattered throughout Mobile, these efficiently transport very large amounts of storm water into creeks, rivers and eventually, Mobile Bay.
The third practice is runoff detention/retention. These are pond-like facilities that collect and hold storm water runoff from commercial properties and suburban neighborhoods to help minimize flooding downstream.
All three practices have their positive points, but White believes there鈥檚 a better way, by actually minimizing storm water runoff through the use of bioinfiltration swales. 鈥淲e call them low-impact development, or LID, for short. LID utilizes 鈥榥atural鈥� solutions, such as vegetation and infiltration, instead of the traditional 鈥榟ardened鈥� solutions that use concrete and steel,鈥� White explained.
鈥淟ID is modeled after nature, designed to manage rainfall at the source using micro-scale controls that mimic a site's predevelopment hydrology,鈥� White elaborated. 鈥淟ID uses techniques that infiltrate, filter, store, evaporate and detain runoff close to its source. Instead of conveying and managing large volumes of storm water, LID addresses it through small, cost-effective landscape features located at the lot level.鈥�
鈥淟ID is modeled after nature, designed to manage rainfall at the source. Instead of conveying and managing large volumes of storm water, LID addresses it through small, cost-effective landscape features located at the lot level.鈥�
In case you鈥檙e thinking this is just a laboratory theory, the concept is already being put into practice on the 吃瓜爆料 campus. With funds from ADEM and the University, five landscaped bioinfiltration swales have been installed between the Whiddon Administration Building and Meisler Hall.
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