Geomorphological Processes and Human Impacts in River Basins (Proceedings of the International Conference held at Solsona, Catalonia, Spain, May 2004). IAHS Publ. 299, 2005., 223-230.

1 Department of Civil Engineering, University of British Columbia, Vancouver, British Columbia, Canada

2 M. Miles and Associates Ltd., Victoria, British Columbia, Canada

Abstract Anecdotal and empirical evidence has long suggested that riparian vegetation can exert an important control on channel width and stability in alluvial rivers. Despite this evidence, the importance of riparian vegetation has yet to gain widespread acceptance. This appears due to several reasons, including the difficulty in quantifying vegetation effects and variation in the sensitivity of alluvial channels to riparian disturbance. In this study we develop a theoretical riparian disturbance sensitivity index, which is tested using 15 before-and-after case studies of gravel-bed rivers in British Columbia, Canada. The majority of the study sites have been subjected to direct riparian disturbance. Observed changes in width, expressed as a percentage of the initial, undisturbed width, correlate strongly with the proposed riparian disturbance index. The three undisturbed reaches show no systematic change in width. We conclude that the riparian disturbance sensitivity index provides a good measure of expected channel sensitivity and change in width following riparian disturbance for gravel-bed rivers in southern British Columbia.

Key words erosion; riparian vegetation; rivers; stability