Dendrogeomorphic possibilities for spatio-temporal reconstruction of the relationship between lateral river erosion and movements of destabilized river banks

Destruction of river banks and gradual lateral fluvial erosion can be closely related processes. This study presents the potential of a unique combination of two dendrogeomorphological (tree-ring and root-ring based) approaches to reconstruct the intensity of lateral river erosion and reconstruct subsequent bank movements. The data on anatomical changes in exposed tree roots and the analysis of the tree-rings eccentricity in tilted trees on the bank allowed to reconstruct seven erosion events over the last 15 years and 17 bank movement events over the last ca. 70 years. The frequency of erosion events was higher compared to bank movement events and, in addition, they occurred in less extreme discharge years. This can be attributed to the high erodibility of the banks, whose sediments contain minimal amounts of clay (demonstrated by grain size analysis). On the contrary, bank movement events were less frequent but occurred almost exclusively during the most extreme flood years. Thus, bank destruction appears to occur after the critical value of bank undercutting by lateral fluvial erosion is exceeded. The findings suggest the possible use of tree rings as a potential indicator of an increased risk of bank destruction.