Assessing Streambed Stability Using D50-Based Stream Power Across Contiguous U.S.

Streambed aggradation and degradation are ways in which a stream will respond to changes in the incoming flow and sediment loads. Several environmental and societal problems are attributed to these channel bed adjustments. Prior studies have extensively used stream power to discern dominant channel processes and establish threshold limits required to trigger channel modifications. However, these studies were constrained by limited datasets and the scope of the applications. The current study used a large dataset of streambed median grain size (D50) across the contiguous U.S. in conjunction with a screening tool to assess the streambed stability for channel erosion and deposition potential. Analysis at the Physiographic Province level indicated major geomorphic changes are highly likely to occur in the Blue Ridge and Pacific Border provinces. Deposition-dominated streams are prominent in the Central Lowland, Great Plains, and Coastal Plain, whereas the Colorado Plateaus and Wyoming Basin have the highest percentage of stable channels. Smoothed spatial maps of stream power indicated the prevalence of high stream power in the Northeast and Pacific Northwest regions of the U.S. Comparison of channel erosion and deposition predictions using the stream power map with actual field calculated aggradation and degradation results yielded a 55% prediction accuracy. Further analysis based on the stream order revealed the association of higher stream power with lower stream orders.