Drainage basin morphometrics for depressional landscapes

Measures of the size, position, and connectivity of depressional wetlands are related to runoff variations among 12 forested catchments on the Canadian Shield under varying moisture conditions. A fine-resolution digital elevation model was used to delineate wetlands within the catchments. Analyses showed that wetland metrics as predictors of runoff variation were superior to catchment area and mean slope, two common basin metrics. The most useful metrics were the area of wetlands in bottomland positions, total wetland area, and volume. During wet periods, catchments containing extensive wetlands were marked by a significant decrease in maximum peak discharge and increase in duration of flow. During mesic and dry periods, catchments containing extensive wetlands were marked by an increase in rise and recession times of peak discharge events and the duration of flows. These characteristics resulted from the interaction between wetlands, their hydrologic connectivity to surface flow paths, and runoff.