Stream power indices correspond poorly with observations of alluvial river channel adjustment

Abstract

AbstractA variety of stream power‐based approaches for predicting catchment‐scale alluvial channel adjustment have been developed. There is an international interest in applying these to inform river catchment management. However, there is some uncertainty regarding their ability to make consistently accurate predictions. This study evaluates the performance of a range of stream power indices for predicting observed channel adjustment. Remotely sensed data were used to generate 33 different stream power indices every 50 m across the networks of five test catchments. The performances of the indices were evaluated by comparing them against observations of erosion and deposition‐dominated channels extracted from the UK's River Habitat Survey (RHS) database. A selection of metrics for evaluating the performance of the indices were calculated. The key finding from this study is that the stream power indices were poorly associated with the observations of alluvial channel adjustment. It is not clear whether this poor association is due to limitations with stream power indices or the suitability of the RHS observations. However, this is not the first study to find a weak association between stream power and observed adjustment. Therefore, caution is recommended to anyone hoping to take advantage of the practicability of stream power indices until further testing is applied using alternative observation datasets. An additional finding from this study is the inconsistency of outcomes between different measures of model performance. It is recommended that future studies also employ multiple model performance measures rather than relying on accuracy alone.