GREEN INFRASTRUCTURE AND LOW IMPACT DEVELOPMENT
Gray infrastructure such as dams , roads , pipes and seawalls have been the most common practices for municipalities to use when combating chronic inundation . As impervious surfaces and gray infrastructure are placed in upland areas during development , the amount of stormwater runoff in a landscape is increased . This is because the naturally permeable soils are covered by impervious gray infrastructure , preventing rainwater from percolating into the ground and running off from the site . As more impervious surfaces are introduced into a watershed , the volume of runoff increases along with the number of pollutants entering receiving bodies of water . This is especially true for areas further downstream which intercept more stormwater runoff volume . Traditionally , limitations on the size of footprints of impervious surfaces , such as buildings , driveways , and other structures , is used to reduce the amount of runoff volume from impervious surfaces .
This practice serves to limit excessive runoff from impervious surfaces , but does not promote rainfall infiltration to represent the drainage conditions pre-development . Also , traditional stormwater management techniques involve moving water at an increased rate and volume through pipes into a receiving body of water .
Increasingly prevalent are efforts to reduce stormwater runoff and promote infiltration through the use of Low Impact Development practices ( LID ) and green infrastructure . The term low impact development refers to systems and practices that use or mimic natural processes that result in the infiltration , evapotranspiration , or use of stormwater in order to protect water quality and associated aquatic habitat ( USEPA ). LID design generally produces a smaller peak rate and runoff volume than traditional “ gray ” stormwater management techniques ( Charleston County , 2017 ). Through LID design , stormwater runoff is managed at the source through landscaped features . The landscaping promotes infiltration , a longer time of concentration and slowed flow rate to create a landscape that is closer to pre-development runoff conditions . The goal of LID is to combine hydrologically functional site design with pollution prevention practices to reduce the impacts development places on the quality and quantity of runoff ( Charleston County , 2017 ). These also incorporate seemingly gray infrastructure practices , such as pervious pavements , which function similarly to undeveloped areas and are considered hybrid gray-green infrastructure alternatives .
GREEN INFRASTRUCTURE AND LOW IMPACT DEVELOPMENT
Green infrastructure is referred to by EPA as areas which manage wet weather flows that use LID practices , as well as the patchwork of natural areas that provide habitat , flood protection , cleaner air and cleaner water . Collectively , LID and green infrastructure are decentralized stormwater management practices which mitigate impacts of stormwater runoff and maintain the structure , function , and integrity of local natural resources . These practices implemented widely within a community can significantly improve the resilience of human communities and provide habitat for diverse wildlife species .
Smaller projects , such as rain gardens or rainwater harvesting systems , can be implemented by property owners to mitigate stormwater on their property . Implementation of larger LID practices often involves Federal , State , County , and municipal governments to ensure National Pollutant Discharge Elimination System ( NPDES ) requirements set by the U . S . Environmental Protection Agency are met . Similarly , smaller LID practices located in close proximity to drainage infrastructure , right-of-ways , or easements may require additional permitting before implementation . For Kiawah Island , the Town of Kiawah Island , the Charleston County Stormwater Program , and the S . C . Department of Health and Environmental Control ( SCDHEC ) enforces regulations for NPDES permitting . Additionally , any projects located in close proximity to wetlands are subject to wetlands jurisdiction and permitting by the U . S . Army Corps of Engineers ( USACE ) and the SCDHEC Office of Ocean and Coastal Resource Management ( SCDHEC-OCRM ). See the following section on living shorelines for additional information on state and federal regulatory controls on wetlands . Any project incorporated within the island-wide drainage system , roads , or right-of-ways on Kiawah Island needs additional permitting from KICA .
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