Wetland Evaluation Project - 140-201

Description: Twenty percent of northern Ontario is covered by wetlands.  We are beginning to recognize their incredible value, and the importance of conserving them, yet we must also meet the needs of a growing population.  The Northern Ontario Provincial Wetland Evaluation System (OWES) is a field-based classification tool that utilizes 50 variables to identify wetlands as either provincially significant or insignificant.  In central Ontario, developers must prepare an Environmental Impact Statement before development near a wetland can commence. However, the cost of using the OWES in a wetland survey can be prohibitively high.

Analysis of the OWES, conducted by Chisholm et al (1997), found that a few of the variables used for classification contribute much more significantly to a wetland’s final score than the others. They also suggested the implementation of a Rapid Assessment Technique (RAT), which could identify priority wetlands without going into the field, and determine the values of some of the variables without even going to the site. The challenge now was to test the accuracy of this new RAT, using GIS and sites previously classified using OWES.


The District Municipality of Muskoka proved to be an ideal study area. The N1A Rapid Assessment Technique model (Chisholm et al 1997) is based on a regression of 28 of the OWES variables, and requires only input for 5 variables. Each wetland was given a score for each of the five variables: Size of Wetland, Rarity of type, Landscape Aesthetics, Open Water Types, and Ownership. The scores for each variable were then summed to calculate a Predicted OWES Score for each wetland complex. Wetlands scoring 600 or more points were considered provincially significant.

The Forestry Research Partnership is excited about the incorporation of GIS into models that assist in decision making.  The Rapid Assessment Technique reduces workload and cost, yet still performs the vital task of classifying our vulnerable wetlands.

The Project Team: Sylvia Strobl, MNR, Brian Naylor, MNR, Adam Hogg, MNR



Report: Developing Mapping and Evaluation Methods for Wetland Conservation in Central Ontario


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