Wetlands Mitigation Targeting Tool
Two GIS based tools have been developed to assist with the selection of sites appropriate for the creation of wetlands. Construction of wetlands for environmental enhancement or mitigation poses great challenges in a rapidly developing landscape. Site selection in the Coastal Plain of Virginia is constrained as much by existing development as hydro-geomorphic processes.
Unlike the early years of the 20th century, compensatory mitigation is now required for wetland impacts. Unfortunately site selection is frequently based on economics rather than good science. There is a demonstrated need, therefore, to develop mechanisms for communicating scientific information and guidance to managers, developers, and regulators at all levels of government. These tools have been developed in response to this need.
The products developed by the Comprehensive Coastal Inventory Program use GIS to target sites in the landscape suitable for wetland creation. It has application for wetland restoration or mitigation projects. The tool outputs selected sites based on a hierarchical protocol developed to evaluate suitability on the basis of five parameters: presence of hydric soils, presence of hydrology, adjacency to existing wetlands, existing landuse and the opportunity for landscape conversion, and proximity to designated conservation areas. A suitability ranking system assigns descriptive values to polygons which meet designated conditions. The application draws from a variety of data sources including the National Wetlands Inventory Program, and the National Land Cover Dataset (NLCD). Since the model was developed for application to large regional areas, classified satellite data is appropriate. NLCD products are derived from Landsat TM with a 30 meter pixel resolution.
The targeting model first addresses hydro-geomorphic requirements for wetland creation (levels 1-2) followed by landuse/landcover conditions (levels 3-4). There are four hierarchical levels and specific conditions must be met at each level. The table below summarizes the hierarchy. In level 3 forest habitat is recognized for its ecological value. Therefore polygons that are agricultural have a slightly higher suitability ranking.
Level |
Conditions Necessary |
Rank |
Level 1 |
hydric soils and hydrology |
potential |
Level 2 |
Level 1, adjacent to wetland |
moderate |
Level 3a
Level 3b
|
Level 2, landcover is forested
Level 2, landuse is agricultural |
good
high |
Level 4a
Level 4b |
Level 3a, adjacent to conservation area
Level 3b, adjacent to conservation area |
high
excellent |
The interactive query product uses ArcIMS technology. This interface allows a user to define certain parameters important to their mitigation/restoration project. Users can specify acreage requirements, preferred hydrologic unit where project should occur, and the locality. The user can also define the level (see table above) at which the search should be made. Queries submitted through this interface will identify polygons that meet these explicit conditions. The application is useful for sorting through a potentially large number of available sites to only a few. Use the "Go To Wetlands Targeting Tool " link below to use this application. Click on the layer label on the map to view metadata.
This project was funded through a Wetlands Development Grant received from the Region III Office of the United States Environmental Protection Agency.
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