Controls on channel sinuosity changes: a case study of the Tisza River, the Great Hungarian Plain

Abstract

The planform geometry of the Tisza, the trunk river of the subsiding Great Hungarian Plain is studied by reconstruction of the last pre-regulation river course. The thalweg sinuosity has been computed for the main alluvial section of the river. Remarkable sinuosity changes have been found to correlate with discharge and sediment load changes at the inflow of tributaries, as well as with active deformation areas, like differential subsidence and wrench fault zones. Analysing the change of the river pattern, a new discrimination line has been derived, which separates the meandering zone on the classic slope vs. discharge diagram into two subzones. The first subzone (lower slope values) corresponds to a range of true, self-organized meandering. The second subzone (higher slope values) corresponds to a range of ‘unorganized meandering’. This is a range where river sinuosity decreases although the channel slope increases. In the case of the Tisza River, this subzone equals to the wandering river pattern.