Constructed Inland Wetlands
Type of Development
New Development, restoration
Topography
Baylands
Longevity
Long Term
Environment
Natural, Urban
Maintenance
Medium
Cost
While the cost of wetland construction can vary considerably, wetland construction is overall low in construction and operation costs when compared with other forms of water treatment.
Overview
Constructing or restoring wetlands aims to recreate natural wetlands – the transitional ecosystems between aquatic and terrestrial systems – in an urban environment, while providing benefits like flood resistance and water purification. Wetlands can occur at a variety of scales. On a larger scale they have the ability to lessen the impacts of sea level rise, sequester large amounts of carbon, lower average temperatures, and provide essential habitats; on a smaller scale they can be used in connection with the natural hydrologic system to control and store excess water and choke points along streams. In Santa Clara County, where many natural wetlands are covered with concrete, small wetlands located slightly inland can be built into these built landscapes to slowly restore the area without removing excessive amount of infrastructure. There will need to be ways that water can reach inland wetlands, such as forebays, which are strips of vegetated or pervious surfaces that can direct water flow in a flooding event to the wetland. Lanes can be placed alongside buildings, parking lots, sidewalks, and streets to direct water and pollutant flow towards inland wetlands.
Function
Wetlands filter water by removing sediment and slowing percolation, cause habitat growth, cool environment, and clean the air.
Benefit
Constructed wetlands reduce flooding by directing water towards habitats rather than impervious structures. As water moves through the system, pollutants are removed and absorbed by plants, sediment settles in the forebay, and groundwater is recharged. Wetlands provide a sanctuary and habitat for native animals and plants. Plants sequester carbon through photosynthesis as well as cool environments by reflecting solar radiation and evapotranspiration, thus lowering heat in the adjacent area by 2 degrees. Linear wetlands allow for special capacities and limit mosquito breeding.
Dependency
Space, Distance from Bay
Development Considerations
Water circulation is needed to prevent stagnant water and placement is key for effective flooding regulation. Usually there is a flood overflow channel, but they work best for small flooding events rather than 100 year floods. It is preferable to build on a slight slope.
Environmental Considerations
Plants, animals and benthic communities are beneficial. In order to have abundant wildlife, place wetland near preexisting natural environments. When considering wetland placement, consider surrounding built environment types, water movement variability, and plant life. It is important to include microorganisms and bugs into wetland habitat for absolute success. Bugs and microrganisms are key to purifying water and creating healthy ecosystems.
Maintenance Consideration
Wetland areas need routine maintence several times a year and after large storms, especially during the first two years. Yearly maintenance on the forebay is needed. The wetlands must have channels for overflow.
Cost Considerations
While the cost of wetland construction can vary considerably, wetland construction is overall low in construction and operation costs when compared with other forms of water treatment.
