Restored Wetlands (NRCS 657)

What is it: 

The return of a wetland and its functions to a close approximation of its original condition as it existed prior to disturbance on a former or degraded wetland site.

Wetland BeforeWetland After   

 

 

 

 

Where is it used: 

This practice applies only to natural wetland sites with hydric soils.

This practice is applicable only where the natural hydrologic conditions can be approximated by modifying drainage, restoring stream/floodplain connectivity, removing diversions, dikes, and levees, and/or by using a natural or artificial water source to provide conditions similar to the original, natural conditions. This practice does not apply to Constructed Wetland (656), Wetland Enhancement (659), Wetland Creation (658), or Wetland Wildlife Habitat Management (644).

Why install it: 
  • To restore wetland function, value, habitat, and diversity.
  • Provide surface water storage capacity within the watershed.
  • Restore natural hydrology to areas that may have been affected by subsurface tile drainage.
  • Reduces downstream exports of nutrients and sediment. Can be combined with upland vegetative buffers for additional filtering of pollutants.
What do I need to know about it: 

Considerations

  • Upon completion, the site shall meet soil, hydrology, vegetation, and habitat conditions of the wetland that previously existed on the site to the extent practicable.
  • Sites suspected of containing hazardous material shall be tested to identify appropriate remedial measures. If remedial measures are not possible or practicable, the practice shall not be planned.
  • Invasive species, federal/state listed noxious plant species, and nuisance species shall be controlled on the site as necessary.
  • Establish vegetative buffers around the wetlands to reduce the movement of sediment and soluble sediment-attached substances carried by runoff.
  • The wetland shall not adversely affect adjacent properties or other water users, the capacity of drainage systems on other properties, and shall not back surface water onto an adjoining property or restrict the capacity of adjacent subsurface drainage systems unless agreed to by signed written letter, easement or permit.
  • Where practicable, existing subsurface drains (tile) shall be rendered inoperable (blocked or removed) or controlled as needed to meet the goals of the restoration and site conditions.
  • Water control structures shall only be used to recreate natural hydrologic patterns or to allow management and maintenance of the desired community.

Soil Considerations

  • Add amendments or mechanical tillage, as appropriate, to promote native vegetative growth.

Hydrology Considerations

  • Natural drawdown through evapotranspiration is preferred over regulating water levels with water control structures. Drawdown of permanent storage is often necessary or desirable to manage wetlands for certain species or during certain times of year.

Vegetation Considerations

  • Vegetative buffers can increase function by trapping sediment, cycling nutrients, and removing pesticides.
  • Prescribed burning can restore wetland and adjacent upland plant communities.
  • Water levels or topography can be manipulated to control unwanted vegetation.

Fish and Wildlife Habitat Considerations

  • When possible, establish vegetated corridors to link the restored wetland to adjacent landscapes, streams, and water bodies and to increase establishment of native vegetation.

Effectiveness 

  • Case studies in Maryland, Illinois, and Iowa indicate wetlands can remove 68% of nitrate-nitrogen and 43% of phosphorus can be retained from drainage water. (Woltemade, 2000)
  • A Minnesota study on constructed wetlands found a 68% and 73% reduction in nitrate-nitrogen and phosphorus, respectively.
  • Crumpton et all. (1993 Iowa) found that constructed wetland mesocosms could reduce N03-N concentrations ranging from 3 to 15 mg/L by >80% during residence times of approximately 1 week.

Costs

  • Costs will vary based on the size of the wetland and existing site conditions.
  • The highest costs are associated with site planning and design, excavation activities, control structures required, tile drain work, and the opportunity cost of any land removed from agricultural production.
  • Cost analyses should take into account the cost of the wetland as well as the acres treated. Estimated life spans of restored wetlands can be 50 years or longer.
  • Average 2016 costs (first year costs and per acre per year) of 1-acre constructed wetland located on land with a high Corn Suitability Rating (CSR 80) treating about 100 acres of drainage, would cost just over $10,000 for design and installation, or just under $800 per acre per year when annualized over a 40-year time period; (Tyndall)
How does it work: 
  • Restored wetlands must be located in historically disturbed or degraded sites that meet the criteria for wetland soils.
  • Water levels can be manipulated for habitat purposes, but cannot be used for crop irrigation or livestock watering.

Operation

  • A monitoring and management plan is required to ensure the wetland maintains hydric soil, water-loving native vegetation, and the presence of water in a manner similar to pre-disturbance conditions. 
  • The plan will include a monitoring schedule and the timing and methods for the use of fertilizers, pesticides, prescribed burning, mechanical treatments, or water control structures.

For scientific literature relevant to restored wetlands, please see the scientific literature on our constructed wetlands page which you can find linked in the 'related practices' to the right.

Design: 
  • Consult your SWCD, NRCS or a wetland contractor as proper siting, vegetation, and construction are critical.
  • General design criteria are established for all purposes that establish minimum embankment heights, spillway requirements, vegetative buffers, and protective cover on disturbed soils.

NRCS Standard 657: Wetland Restoration