M3L7Wetland

Module III

Lesson Seven: Structural BMPs

Stormwater Wetlands

Stormwater wetlands are constructed basins that have a permanent shallow pool of water throughout the year (or at least throughout the wet season) and create suitable condition for the growth of marsh plants. They are designed to maximize pollutants removal through marsh uptake, retention, and settling. In contrast to wet ponds, stormwater wetlands are shallower in depth and have more vegetation coverage. However, using a natural wetland for stormwater management is discouraged due to possible disturbance of the natural balance of the ecological system.

The possible adverse effects of using wetlands as one of the stormwater BMPs are the potential for blocking fish passage, potential habitation by undesirable species (vegetations and animals), and potential groundwater contamination. Waterfowls may become undesirable year-round residents of the wetland, increase the nutrient and coliform loadings to the wetland, become a nuisance to the residents, and present a possible safety hazard to airplanes. Click here for the detail report on Federal Aviation Administration National Wildlife Strike Database Serial Report Number 10, 2004. The potential nuisance and hazards can be prevented via:

Increasing structural complexity design to limit the deep and open water area and grassy areas favored by waterfowls
Maintaining and/or plating upland buffer zones to reduce the introduction of nuisance plant species
Planting emergent vegetation to reduce nuisance algal blooms
Using Gambusia fish in warmer climates and black striped topminnow (Notrophus fundulus) in colder climates for mosquito control
Growing short (vs. tall ) plants to minimize protection of pests from their predators by taller plans

Click here for the detailed design of stormwater wetlands from EPA’s Storm Water Technology Fact Sheet: Storm Water Wetlands.

Click here to view the removal efficiencies of constructed wetlands systems.

Source: Image of EPA Wetlands Fact Sheet