Christopher Harrington
GIS Application for Aquatic Barrier Mitigation in the Upper Thames River Watershed © 2006
The Upper Thames River watershed, like most watersheds in Southern Ontario, has many dams and barriers within its boundaries that can have adverse effects on the aquatic ecosystem. In many cases, the dams and barriers are in poor condition and no longer serve the purpose for which they were originally constructed. Removal or mitigation of such structures is an effective tool for the restoration of river systems. Significant resources are required to mitigate the ecological impacts, limiting the amount of rehabilitation work that can be undertaken. Targeting mitigation efforts for the greatest improvements in aquatic ecosystem health is necessary. Characteristics of the dams/barriers alone are not sufficient to identify their impact. Spatial variation in the type and quality of aquatic ecosystems in their proximity must also be considered.
In this research the impacts of aquatic dams and barriers have been quantified using watershed analysis tools available within Geographic Information Systems (GIS). An ecological approach is employed to consider the cumulative impacts of barriers adapting a watershed concept to more localized barrier catchments. Analysis that utilized fourteen criteria to prioritize dams and barriers for mitigation efforts was undertaken. Working with a hydrologically conditioned DEM, a watershed model was developed and used in combination with a dam and barrier inventory for the Upper Thames River Watershed to develop catchment areas for each dam and barrier.
With spatial refinements to the inventory data, the watershed model was successfully used to define catchments for 128 barrier sites in the watershed. These catchments provide the first step in the analysis conducted to consider the full spatial extent of the ecological impacts associated with the dams/barriers. Using existing watercourse data, GIS overlay analysis was used to summarize conditions in each barrier catchment. These characteristics are considered in combination with other criteria specific to each dam or barrier to develop a priority list of structures to consider for mitigation efforts.