Response of lateral channel dynamics of a lowland meandering river to engineering-derived adjustments - an example of the Morava River (Czech Republic)

摘要

Freely meandering (quasi)natural reaches oflowland rivers represent a rare phenomenon in Central Europe.Increasing attention is currently being paid to thedynamics of quasi-natural (artificially influenced) meanderingrivers as this attention represents the basic prerequisitefor the development of appropriate restorationstrategies on regulated rivers. This study focused on a 5.5km long reach of the Morava River in the Strá?nické Pomoravíregion, Czech Republic that is characterised byquasi-natural evolution after substantial engineering adjustmentswere made in the first decades of the twentiethcentury. Based on Geographic Information Systems (GIS)analysis of aerial photographs, the spatio-temporal dynamicsof bank erosion and accretion rates were quantitativelydescribed and variables that control channel migrationrates were identified. High rates of lateral shifts werelocalised in high sinuosity segments (sinuosity 1.17-2.37),whereas segments with very low rates were straight orformed into slightly curved bends (sinuosity 1.05-1.18). Asa key factor, engineering works that influenced local riverbed slope and induced a dramatic increase in bank erosionrates were identified. River engineering works induced adramatic increase in bank erosion rate (2.19 m/year for1938-53 and 1.47 m/year for 1953-63). An interval of approximately25 years was needed before the erosion ratesdropped back to values documented before river regulation(0.35-1.09 m/year for 1841-1938). Other important controllingvariables included radius of curvature, frequencyand magnitude of floods and, locally, river bank materialproperties and floodplain land cover.