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Justin Hawley March, GIS Rangers
To better assess relationships within a wetland, GIS Rangers, in partnership with the Coon Creek Watershed District, has
developed a geoprocessing method that analyzes wetland functional capacity with the use of readily available inputs.
This method can be deployed in almost any environment, and examines the overall relationship between all wetland
components, rather than individual components by themselves.The method utilizes the process put forth in “A Rapid
Procedure for Assessing Wetland Functional Capacity base on Hydrogeomorphic (HGM) Classification” by Dennis W.
Magee. In this process, individual variables of the environment are analyzed and evaluated in terms of the type of
landscape they are found in.These individual variables are then assigned a value dependent not only upon the
landscape position, but upon the type of preliminary analysis being done. Preliminary analyses put forward in the HGM
method include groundwater recharge, wildlife abundance, storm water storage, and several others. Once the preliminary
analyses are performed to get separate, independent, functional valuations, the individual analyses are then easily
summed into a total functional capacity. In terms of GIS processing, the method utilizes readily-available vector files
such as the National Wetland Inventory, the NRCS Soil Survey, as well as localized data such as elevation and land use.
These vector files are evaluated and categorized into types denoted by the “Rapid Assessment Procedure.”The types are
then assigned a “Functional Value” (Generally a value between 1 and 3).With the Functional Value established, these
vector files are converted to raster format.These raster files are then “added” together with the use of raster math giving a summarized functional value for each pixel.This approach combines the benefits of scalability, portability and modularity to accomplish the evaluation of functional capacity of a given wetland, watershed, or region.
Edited presentation from the one given at the Wisconsin Land Information Association 2012 conference to be able to upload. Please feel free to contact us using the phone numbers or email addresses listed in the presentation to ask questions, discuss, or criticize.