- Published: 12 February 2013
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Wetlands perform a variety of functions including groundwater recharge, flood flow attenuation and water quality protection. Land use changes surrounding wetlands may increase the flow of water and pollutants to wetlands, overwhelming their ability to provide these functions and threatening their sustainability. As a result, communities are looking for mechanisms to manage the impact of land use changes surrounding wetlands while allowing for continued growth. This handout summarizes wetland functions and several Best Management Practices available to protect wetlands as surrounding land use changes.
Ground Water Recharge
Wetlands allow for the gradual recharge of aquifers, regulate groundwater levels and moderate flows into and out of underground water supplies.
Flood Flow Attenuation
Loss of floodplain forested wetlands and confinement by levees have reduced the floodwater storage capacity of the Mississippi River by 80 percent, significantly increasing the potential for flood damage (Gosselink et al.1981).
Based on a 1976 study by the U.S. Army Corps of Engineers of the Charles River Basin near Boston, Massachusetts, the Corps purchased 8500 acres of wetlands for $7,300,000 in lieu of building a $30,000,000 flood control structure (Thibodeau and Ostro, 1981).
Water Quality Protection
By reducing flood flows and the velocity of flood waters, wetlands reduce the amount of sediments carried by rivers and creeks. This process which removes sediments from flood waters also acts to remove sediments from overland runoff as it passes through wetlands and into rivers and streams.
Wetlands act as natural filters, removing nutrients and some chemical contaminatents from surface and ground water. This provides rich habitat for plant growth and also reduces non-point pollution in rivers and streams.
Wetlands provide unique habitat for wildlife species, many of which are either endangered or threatened and provide opportunities for education, scientific study and recreation.
Best Management Practices For Wetland Protection
Wetland Setbacks: A setback of some distances (100 feet, 50 feet, etc) depending on wetland function, from delineated wetland area. Restrictions in the area may include limitations on structures and mowing.
A 98 foot buffer strip between logging activity and wetlands in Pennsylvania removed an annual average of approximately 75-80 percent of the suspended sediment in storm water (Lynch et al., 1985).
A wetland area surrounded by impervious cover is unlikely to maintain wetland functions. Rapid runoff from impervious areas will bring sediments and pollutants into wetlands, degrading it. The increased speed of runoff from impervious surfaces will dislodge wetland soils and vegetation, reducing the structural integrity of the wetland (Chesapeake Bay Program, 1997).
Many wetlands are found near to or adjacent to streams and rivers. Protecting riparian areas may benefit both the stream and wetlands associated with that stream by:
- Reducing the amount of storm water associated pollutants entering wetlands,
- Reducing the potential for downstream wetland degradation resulting from erosion associated with peak storm water flows,
- Maintaining slope stability adjacent to wetlands and stream,
- Providing a buffer between wetlands and adjacent land uses, and
- Protecting aquatic life by preventing and reducing thermal warming impacts.
(U.S. EPA, Office of Water Protecting Natural Wetlands: A Guide to Storm water Best Management Practices EPA-843-B-96-001, October, 1996)
Reduction in Impervious Cover: Important to note that buffers alone may not adequately attenuate concentrated peak storm water flows to wetlands. As a result, wetlands buffers are only one of many site design practices that should be used on a site to protect the natural services wetlands provide.
Pollution Prevention: Measures to reduce the discharge of pollutants. Pollution prevention may be implemented through educational, volunteer and incentive programs as well as through local policies and regulations. The following activities may produce non-point pollutants:
- Lawn and garden activities including the application of lawn care products
- Discharge of pollutants into storm drains including waste oils and litter
- Improper operation and maintenance of septic systems
- Lack of erosion and sediment control during construction
A Wetlands Management Plan - All Hangs On Classification of Wetlands
Classify wetlands based on information regarding function (flood attenuation, stream bank erosion control, non-point pollution control, ground water recharge).
- Classification may also consider public preference for management and practicable alternatives to development in wetlands.
- Provide the basis for reasonable and defensible decisions about protection and development of and surrounding wetlands.
- Increase permit predictability for wetlands property owners, and
- Reduce processing time and controversy related to wetland permits.
- (Juneau Wetlands Management Plan, City and Borough of Juneau Community Development Department, February 1997)
- CBJ Wetlands Management Plan
- The study area included in CBJ’s plan is all those wetlands delineated by the Corps.
- Permitting for those wetlands that have not been mapped, evaluated or categorized by the Juneau Wetlands Management Plan is administered by the Corps under §404 of CWA.
- CBJ’s plan designates those wetlands that are more suitable for development and those that are less suitable for development, in advance of any specific development proposal
- Wetland management categories are agreed to by the CBJ, State of Alaska and federal regulatory agencies.
- Corps issued a General Permit based on wetlands covered by the plan and authorized the CBJ to administer the General Permit. The two highest quality wetlands under the CBJ plan are covered by Individual permits from the Corps only. If an activity is covered by NWP, no local wetlands permit is required if the activity is conducted in accordance with the NWP.
- Deals with development IN wetlands not necessarily SURROUNDING wetlands.
- Development Surrounding Wetlands - Best Management Practices to Protect Wetlands During Development Include - Filtration Curtains shall be used to protect streams from turbidity due to disturbance of adjacent soils.
- Existing wetland vegetation should be striped in mats and repositioned over regareded soil.
- Hydrology surrounding the discharge site should be maintained with the use of culverts, if necessary. Activities should not adversely impact adjacent wetlands by causing ponding, drainage, siltation or inadvertent fill.
- Erosion at the construction site shall be controlled through re-vegetation and other means. Exposed soils shall be re-vegetated in one year.