A GIS-based approach to mapping probabilities of river bank erosion: Regulated River Tummel, Scotland

This study explores the use of Geographic Information Systems (GIS) techniq ues for mapping river channel planform change and bank erosion probability. The method used is primarily based on an approach developed by Graf (Graf, W.L. 1984. 'A probabilistic approach to the spatial assessment of river ch annel instability', Water Resour. Res., 20(7), 953-962), which proposed tha t bank erosion probability could be determined for any given cell on a floo dplain by taking into account (i) its distance laterally and in the upstrea m direction to the active river channel, and (ii) a value representing floo d magnitudes for the given period. In this study, Graf's method is refined by using a GIS approach and by incorporating the influence of geomorphic va riables, such as river bank morphology, sediment type and floodplain vegeta tion, on bank erosion rates. In addition, the technique is applied to a wan dering gravel-bed river of roughly 80 m width, representing a different typ e and size of river to that used in Graf's study. Thus, the wider applicabi lity of the technique is tested. In addition, the analysis here covers only a short time scale (1988-1994) compared with that used by Graf. The high t emporal resolution of this study is enabled by the use of aerial photograph y and also by the substantial channel changes that occurred within this tim e period as a result of several high magnitude flood events. The results of the study indicate the usefulness and validity of the approach, particular ly with regard to floodplain erosion hazard mapping and the assessment of t he effects of altered flood regimes and land use. Copyright (C) 2000 John W iley & Sons, Ltd.