Geographical information systems techniques to channel slope delineation in Minnesota

Our goal is to evaluate automated methods to estimate channel gradient, and to develop estimates of flood discharge and frequency for unregulated streams within Minnesota. Approximately 60% of equations developed by the US Geological Survey use channel gradient to estimate flood discharge. Studies have also demonstrated relationships between the gradient of stream channels and fish community composition. Twenty-one of 35 habitat features in Wyoming streams were related to channel gradient. Channel gradient is used to calculate stream power. Stream power, in turn, is used to estimate erosive capacity. Increased erosive capacity in reaches with higher gradients can increase sedimentation in downstream, lower gradient reaches. Sedimentation is a limiting factor of fish habitat and can negatively effect macroinvertebrates. Increased turbidity may decrease the feeding success of predatory fish. Although field techniques to measure channel gradient are standardized, several techniques to estimate stream gradient using a GIS exist, but a standard technique has not been chosen. The objectives are to: determine a method for measuring channel gradient that provides similar estimates to measured flood discharges using regression equations, and identify GIS method(s) that provide similar estimates to measurements made in the field with standard techniques.