The morphodynamics of the lower River Vecht, the Netherlands, and the influence of geomorphological setting and bank composition on meander migration were studied by means of reconstructing the pre-channelization landform configuration on a scale of 1 : 25,000, using historical maps from 1720, 1850 and 1890 A.D. and other data.
A downstream sequence of reaches was observed, each with a typical fluvial style and channel migration rate: (a) a narrow meander belt and a highly sinuous channel with intermediate migration rate, in the middle of an extensive floodbasin; (b) a wide meander belt and high rates of lateral channel migration, especially where large meanders impinged upon valley bluffs, as part of an incised setting; (c) a low sinuosity, embanked channel with low rates of downstream migration because of confinement by dikes, occurring in an inland delta with sandy sediments.
Local variation in meander migration rates was observed within reach B. This was caused by the spatial variability of bank resistance as reflected by the width-depth ratio of the channel and the silt-clay ratios of deposits. River banks are: 1) very erodible when consisting of channel deposits, aeolian dune deposits or when coarse fluvio-periglacial deposits occur at their base; 2) erodible when dominated by overbank deposits or aeolian sand sheet deposits; 3) resistant when a plaggen-layer is exposed; and 4) very resistant when dominated by floodbasin deposits.
These implications of meander variability enable to assess the effects of the rehabilitation of the meandering process.