Home 3. Identify Priority Wetlands

Identify Priority Sites for Wetland Conservation and/or Restoration

Once your community has an updated local wetland map, identifying priority wetland sites for conservation and/or restoration is an important step to guide decisions about how to target wetland programs, funding, and local regulations.  This step is especially useful for communities with extensive wetland resources who wish to accommodate future growth while protecting the most sensitive or valuable lands. It is recommended that communities include prioritization of wetlands as part of broader-scale conservation and/or restoration planning efforts. This may include watershed plans, regional green infrastructure assessments, wildlife action plans, and habitat conservation plans.

This analysis can also be conducted as part of a service provided by the U.S. Fish and Wildlife Service (FWS), its primary cooperator, Virginia Tech’s Conservation Management Institute, or an organization or firm with experience in these techniques.  This service generates an historical assessment of pre-settlement wetland types, acreage, functions and general trends; a watershed characterization of current wetland status and functions; and an identification of potential wetland restoration sites.  Costs for these services vary with the type and density of wetlands in a geographic area, the amount of historic loss, the age of the NWI data, and the availability of digital data sources (e.g., land use/cover and soils). 

The criteria used to prioritize sites for conservation and restoration is different, but the overall process is the same:

  1. Identify potential sites for conservation/restoration from local wetland maps
  2. Rank sites based on specific criteria derived from mapping
  3. Evaluate top sites (or all sites) in the field to collect more detailed site information (optional)
  4. Revise ranking to reflect field conditions (optional)

Note that if the process of updating your wetland maps has resulted in a new map of ‘potential wetlands,’ there are three options for dealing with these sites in the ranking exercise: 1) field-verify all potential wetlands before including them in the ranking; 2) rank these sites separately; or 3) leave these sites out of the ranking entirely, and evaluate them on a case-by-case basis over time as resources become available to conduct field verifications.

Step 1. Identify potential sites for conservation/restoration from local wetland maps

To identify potential sites for wetland conservation, we suggest that communities begin by using their local wetland maps and making a preliminary assessment of wetland function to identify specific wetlands that have high or moderate potential to provide the functions of interest to the community (e.g., flood control, shoreline protection).  The preliminary assessment of wetland function assigns wetland functions to wetlands in the community by adding abiotic and landscape feature descriptors through a desktop GIS exercise.  While field assessments of individual wetlands are necessary to more accurately evaluate wetland functions, a remote sensing approach to estimate wetland function provides a cost-effective way to rapidly identify priority sites for conservation and/or restoration. It is considered preliminary because on-the-ground conditions can affect wetland functions and these must be evaluated in the field (see Step 3).

Potential sites for wetland restoration include former wetlands or existing degraded wetlands.  These can be identified using maps of historic wetlands, and local wetland maps using a method described by Tiner (2005). Potential restoration sites include:

Former wetlands with:

  • effectively drained hydric soil map units
  • filled areas with no development
  • impounded areas
  • excavated areas
  • farmed wetlands

Degraded wetlands that are:

  • partly drained
  • impounded
  • excavated
  • farmed
  • tidally restricted

The results of this step are maps of potential wetland conservation and restoration sites.

Step 2. Rank sites based on specific criteria derived from mapping

Because not all potential sites identified in Step 1 can actually be conserved or restored due to cost and other factors, ranking criteria are used to prioritize sites. Communities should develop wetland ranking criteria that reflect local goals, regulatory requirements, community interest, and/or wetland characteristics.  In general, ranking criteria that relate to environmental benefits, feasibility and community benefits of the proposed project, as well as development pressure on individual sites should be considered.  Table 3.1 provides some example ranking criteria for wetland conservation and restoration sites.

Table 3.1. Example Ranking Criteria for Wetland Conservation and Restoration Sites

Wetland Conservation

Wetland Restoration

  • Located in priority watershed/subwatershed
  • Located in headwaters, stream valley, floodplain
  • Adjacent to existing wetland or protected land
  • Landowner willingness to sell or donate
  • Low project cost/acre
  • High community acceptance of project
  • High ecological significance (e.g., rare wetland type or habitat for RTE species)
  • Currently unprotected
  • Vulnerability to development pressure
  • Wetland type is highly sensitive to changes in hydrology/pollutant inputs (e.g., bogs, fens)

 

  • High potential to provide functions of interest
  • Low potential for impacts from surrounding areas
Of the criteria listed in Table 3.1, at a minimum, communities should evaluate vulnerability to impacts from development and include this as a major factor for ranking conservation sites so that those valuable wetlands with a high likelihood of being developed can be protected if possible.  A spreadsheet is helpful for this ranking exercise, and communities can determine how to score each criterion and assign each a different weight if desired.

The ranking results in a list and map of sites that are the highest priorities for conservation and/or restoration.  For communities with limited funds for wetland protection, this ranking can serve as the basis for a local wetland conservation or restoration program. However, because the ranking is primarily based on mapping data, it is also helpful to visit the top priority sites in the field to verify wetland presence, further evaluate function and collect additional data to refine the ranking. Therefore, communities with additional resources may wish to continue on to Steps 3 and 4. 

Step 3. Evaluate top sites (or all sites) in the field to collect more detailed site information

Field assessments can be used to confirm the assumptions made in Steps 1 and 2 about the presence, function, and condition of individual wetlands. Site visits can also be used to further evaluate restoration feasibility. For example, site evaluation for restoration potential can tell you whether the causes of impacts are known and controllable, whether the hydrology is suitable for restoration, and give you a sense of the complexity of the proposed restoration project.

Given the complexity of most wetland assessment methods and the expertise and time needed to conduct them, it may not be realistic to assess all potential wetland conservation and restoration sites in the field. This is where the ranking in Step 2 comes in handy to help narrow down the number of sites that are field-assessed.

Step 4. Revise ranking to reflect field conditions

Results of field assessments should be used to update the spreadsheet ranking and maps of priority wetland conservation and restoration sites.  This may mean deleting sites from the list that have since been developed, or that do not concur with the initial functional assessment. It could also include adding criteria to the ranking and re-ranking the sites based on new, more detailed, information collected in the field. 

Additional guidance for this Step of the WARPT is provided in the following 3 sub steps:

After identifying priority wetlands for protection and restoration, the next step is to protect wetlands locally using regulatory or voluntary measures.

 
Digitize
The process of converting features on a paper map into digital format using a trace methodology, which results in the creation of a spatial dataset.
Ecotone

A transition area between two adjacent, but different plant communities.

Indirect Wetland Impacts
Impact to wetlands caused by inputs of stormwater and pollutants generated by land development or other activities within the wetland CDA.
Direct Wetland Impacts
Wetland loss or degradation resulting from activities that occur within wetlands, such as dredging, filling and draining.  Activities that cause direct impacts are largely regulated through the federal and state wetland permitting process.
Stormwater Treatment Practices

A structural or non-structural practice designed to temporarily store or treat stormwater runoff in order to mitigate flooding, reduce pollution, and provide other amenities (also called a Best Management Practice – BMP).

Hydrogeomorphic
Factors that influence how wetlands function, including geomorphic setting, water source, and hydrodynamics.
Hydrogeomorphic
Factors that influence how wetlands function, including geomorphic setting, water source, and hydrodynamics.
Sinks
A cell or set of spatially connected cells that cannot be assigned flow direction in a raster elevation dataset. This can occur when all neighboring cells are higher than the processing cell or when two cells flow into one another. Sinks can indicate areas where water is likely to pond, but can also be an error in the dataset.
Facultative Wetland Plants
Species that usually occur in wetlands (approximately 67% - 99% probability), but also occur in non-wetland areas (approximately 1% - 33% probability).
Obligate Wetland Plants
Species that occur almost always in wetlands under natural conditions (greater than 99% probability), but which may also occur rarely in non-wetlands (less than 1% probability).
Interferometric Synthetic Aperture Radar (IFSAR)
A radar technique that uses two or more synthetic aperture radar (SAR) images to generate surface elevation using differences in the phase of waves returning to the satellite or aircraft.
Interferometric Synthetic Aperture Radar (IFSAR)
A radar technique that uses two or more synthetic aperture radar (SAR) images to generate surface elevation using differences in the phase of waves returning to the satellite or aircraft.
Light Detection and Ranging (LiDAR)

A remote sensing technique that measures properties of pulsed laser light reflected from objects to determine their position, velocity, and other information.

Light Detection and Ranging (LiDAR)

A remote sensing technique that measures properties of pulsed laser light reflected from objects to determine their position, velocity, and other information.

Light Detection and Ranging (LiDAR)

A remote sensing technique that measures properties of pulsed laser light reflected from objects to determine their position, velocity, and other information.

Digital Elevation Model (DEM)
A digital file consisting of terrain elevations for ground positions at regularly spaced horizontal intervals.
Digital Elevation Model (DEM)
A digital file consisting of terrain elevations for ground positions at regularly spaced horizontal intervals.
Hyperspectral Data

Information collected and processed from across the electromagnetic spectrum. Spectral signatures (unique “fingerprint” left by specific objects) enable identification of materials that make up a scanned object.

Remote Sensing
Gathering and recording information about objects without actual contact through the use of such techniques as photography, infra-red imagery, and radar.
Hydrophytes
A plant that grows wholly or partially submerged in water.
Blackspots
Areas on aerial photos that show up as dark blue, dark grey, or black and are indicative of saturated soil conditions.
Stereoscopic
The ability to see three dimensionally by using two views of a single object from slightly different positions typically through the use of an optical aid known as a stereoscope.
Hydric Soils
Soils that are saturated, flooded, or ponded for a long enough period during the growing season to develop anaerobic conditions in the upper soil horizons.
Hydric Soils
Soils that are saturated, flooded, or ponded for a long enough period during the growing season to develop anaerobic conditions in the upper soil horizons.
Hydric Soils
Soils that are saturated, flooded, or ponded for a long enough period during the growing season to develop anaerobic conditions in the upper soil horizons.
Hydric Soils
Soils that are saturated, flooded, or ponded for a long enough period during the growing season to develop anaerobic conditions in the upper soil horizons.
Hydric Soils
Soils that are saturated, flooded, or ponded for a long enough period during the growing season to develop anaerobic conditions in the upper soil horizons.
Hydric Soils
Soils that are saturated, flooded, or ponded for a long enough period during the growing season to develop anaerobic conditions in the upper soil horizons.
Hydric Soils
Soils that are saturated, flooded, or ponded for a long enough period during the growing season to develop anaerobic conditions in the upper soil horizons.
Hydric Soils
Soils that are saturated, flooded, or ponded for a long enough period during the growing season to develop anaerobic conditions in the upper soil horizons.
Geographic Information Systems (GIS)

A system that integrates hardware, software, and data for capturing, managing, analyzing, and displaying all forms of geographically referenced information.

Geographic Information Systems (GIS)

A system that integrates hardware, software, and data for capturing, managing, analyzing, and displaying all forms of geographically referenced information.

Digitize
The process of converting features on a paper map into digital format using a trace methodology, which results in the creation of a spatial dataset.
Minimum Mapping Unit

The minimum size or dimensions for features to be mapped as lines or areas for a given map scale.