Constructed Stormwater Wetland
Constructed Stormwater Wetland in Boone
The Town of Boone, Watauga County Cooperative Extension, and NCSU Biological and Agricultural Engineering worked together with funds from the NC Clean Water Management Trust Fund to construct a wetland to mitigate stormwater runoff from entering the New River. Stormwater runoff is one of the leading causes of surface water quality degradation in the nation, and the New River is no exception. Every time it rains our rivers and streams are exposed to pollutants such as oil and gas from roads, trash and debris, pet waste, sediment from erosion, and excess nutrients and chemicals. Stormwater runoff also produces thermal pollution, degrading river habitat for trout in the mountains.
This constructed stormwater project consists of a one acre wetland in the floodplain to treat stormwater from 30 acres of impervious parking lots, roads, buildings and even runoff from the newly constructed baseball fields. Stormwater wetlands are effective environmental protection practices because they remove sediments, nutrients, metals, chemicals, and bacteria from stormwater. The Stormwater Wetland Design Update published by the North Carolina Cooperative Extension Service indicates that a well vegetated stormwater wetland will reduce outflow temperatures by 3 to 5°F more than wet ponds, which will be good for our trout streams.
The Boone wetland was designed to capture and treat the runoff produced by the first flush (precipitation = 1.2 inches) because that is where the rain picks up most of the pollutants. A flashboard riser outlet structure was sized to drawdown this volume of water over a 72-hour period to optimize the stormwater treatment. The constructed wetland consists of deep pools, shallow water, and temporary inundation areas that create a diverse ecosystem for wetland plants and animals.
Click here for a list of the native vegetation planted in the Boone Stormwater Wetland.
The wetland has a diverse variety of native herbaceous obligate and facultative wetland species planted by volunteers. Over 50 different species in all will be planted and seeded for diversity; everything from swamp butterfly weed, marsh hibiscus, and pickerelweed- basically lots of beautiful flowering plants to create habitat for mosquito predators.
We have all heard the warnings: Don’t let standing water collect because it breeds mosquitoes. This is true, mosquitoes require shallow, stagnant, anaerobic water conditions. Adult females find environments such as puddles or containers where they will find high nutrients and bacteria to lay their eggs. Many people perceive that wetlands are breeding grounds for mosquitoes. This is usually not true. There is growing evidence to show that healthy functioning wetlands can actually reduce mosquito populations. Healthy wetlands provide habitat for dragonflies and their larvae, frogs, birds, and other mosquito predators. Mosquitoes only become a problem in areas that don’t support these beneficial species. Wetland restoration and manmade wetlands can reduce the mosquito population in two ways: 1) provide proper habitat for natural enemies of mosquitoes, and 2) prevent flooding in areas that aren’t normally wet and thus support mosquitoes but not their predators.
A viable healthy ecosystem has been created within the Town of Boone and will be conserved in perpetuity. Educational signage will be installed to inform greenway visitors about stream and wetland ecology, watersheds, clean water, native plants, and natural resources protection. The Town of Boone will also be installing benches and trails to observe the wetland. This conserved land will benefit the river ecosystem for years to come.