Improved estimation of wetland cover in the western Canadian boreal forest

Abstract

The Alberta Wetland Inventory (AWI), which is used in a variety of applications across the province to estimate wetland cover from aerial photographs, detected only 34% of confirmed wetland field plots in boreal forest watersheds in the Swan Hills of Alberta. Given the association between wetland cover and runoff and surface water chemistry in western Canadian boreal forest (Boreal Plain) watersheds, accurate quantification of wetland cover is critical to efforts to model hydrologic processes and water quality. Therefore, as a component of the Forest Watershed and Riparian Disturbance (FORWARD) Project, the Wetland Inventory and Identification Tool (WIIT) was developed and successfully detected 81% of the wetland field plots. Application of both models across a variety of landscapes in the boreal forest of Alberta demonstrated that wetland cover estimates were 1.5 times higher with the new WIIT model than with AWI. Also, WIIT identified polygons that were both smaller and contained taller trees than those identified by AWI, indicating that this computer model may be more effective than wetland identification methods that use only aerial photography. Results of this study show that careful interpretation of aerial photographs at the 1:15,000 scale, coupled with ground truthing and computer models, can provide an accurate means of identifying wetlands on Boreal Plain landscapes.