The NRCS defines wetland enhancement as, the rehabilitation or reestablishment of a degraded wetland or modifying the conditions of a specific wetland to meet the needs of a specific species or purpose. Wetland enhancement is intended to provide favorable wetland conditions to targeted species. These conditions include, hydrologic enhancement of the soil, how deep, how long, and when the soil is saturated, as well as vegetative enhancements as simple as replacing unwanted species with a desired species.
Wetland enhancement is performed on any existing wetland regardless of the level of degradation to enhance the functions of the wetland. However, wetland enhancement does not apply to other conservation practices such as; 657 Wetland Restoration, or 658 Wetland Creation, nor does it apply to the treatment of water pollution, 656 Constructed Wetland.
When considering wetland enhancement for hydrologic enhancement, care must be taken to ensure that there is an adequate source of water to meet the intended enhancement goal. Often the installation of water control systems that regulate water levels and timing is required to meet the hydrologic conditions for vegetation and wildlife. Previously existing drainage systems may require removal or modification. Parameters to consider when designing a water control structure are covered in conservation practice 410 Grade Stabilization, 587 Structure for Water Control, and conservation practice 657 Wetland Restoration defines embankment design.
Wetland enhancement considerations for vegetation enhancement include plant selection, site preparation, and species colonization rate. When preforming wetland enhancement where the site will require planting new or additional vegetation, priority must be given to native vegetation adapted to the saturated conditions of a wetland. Invasive, noxious, and nuisance species should be controlled prior to the wetland enhancement. Some wetland enhancement sites will not require planting, if the selected native species will dominate the site within 5 years, the site may be left to regenerate naturally. If the restoration site is known to have contamination from nutrients or pesticides, chosen species should be tolerant to these conditions, however if the site is contaminated with hazardous materials, it must be cleaned prior to beginning wetland enhancement. Normal seeding practices such as, mechanical or aerial seeding, organic mats, and topsoiling to establish new vegetation may be used in wetland enhancement, so long as there is adequate substrate material. If the wetland enhancement site’s native vegetation is primarily herbaceous vegetation, several different species should be chosen. If the wetland enhancement site is forested, when possible, 6 or more species adapted to the site should be chosen for reforestation.
The NRCS has an extensive list of considerations to examine before establishing a wetland enhancement:
- Replace existing drainage structures for long term (greater than 15 years) easements such as the Wetland Reserve Program.
- Existing wells not used to supplement wetland hydrology should be decommissioned to prevent ground water contamination.
- Manipulation of water levels to control unwanted vegetation.
- Existing wetland functions and/or values that may be adversely impacted.
- Effect enhancement will have on disease vectors such as mosquitoes.
- Effects on downstream flows or aquifers that would affect other water uses or users.
- Effect of volumes and rates of runoff, infiltration, evaporation and transpiration on the water budget.
- Effects on fish and wildlife habitats that would be associated with the practice.
- Linking wetlands by corridors wherever appropriate to enhance the wetland’s use and colonization by the flora and fauna.
- When determining which species to plant, consider microtopography and the different hydrology levels.
- The effects that location, installation and management may have on subsurface cultural resources.
- The effect of water control structures on the ability of fish to move in and out of the wetland.
- Effects on temperature of water resources to prevent undesired effects on aquatic and wildlife communities.
- Timing of water control to mimic the natural hydrological regime of the area, further enhancing the habitat for aquatic species.
- Design modifications that will limit potential negative impacts of wetland plants and animals on the project.
- Biological control of undesirable plant species and pests should be implemented where available and feasible.
- Inspection schedule for embankments and structures for damage assessment.
- Depth of sediment accumulation to be allowed before removal is required.
If conditions for wetland enhancement exist, there are financial incentive programs which may cost-share the expenses of the additional requirements. Implementation of conservation cover can be worked into an EQIP application package and may complement other conservation practices such as 356-dike, 657-wetland restoration, 410-grade stabilization, 612-tree/shrub establishment, 580-streambank and shoreline protection, 584-stream channel stabilization, 391-ripariian forest buffer, 393-filter strip, 390-riparian herbaceous cover, and 587-structure for water control.
In summary, wetland enhancement is an important conservation and production practice that can be utilized in conservation programs. Wetland enhancement rehabilitates or re-establishes degraded wetlands. Wetland enhancement provides habitat for many different species of wildlife. Careful selection of the proper native plant species, best suited for the selected site will provide the greatest benefits, restoring prosperity, and increases species diversity to degraded wetlands. For more information contact your local County Extension Office or your local USDA Service Center.