Diagrams of elementary morphological effects

The elementary morphological response to pressures and measures can be understood from the simplified diagrams given below. These diagrams are valid primarily for larger sand-bed rivers, because they do not include the response of channel width, bed sediment composition and vegetation. Nonetheless, they are also very useful in understanding the long-term and long-distance response of smaller rivers with gravel beds or active interactions with vegetation. It is just that those rivers require additional interpretation, for instance by realizing that bed erosion may favour vegetation encroachment and thereby further erosion because the vegetation concentrates flood flows in a narrower part of the cross-section. The diagrams reveal in particular how far-away upstream and downstream parts of a river are affected by local pressures or measures. Background theory is given by Jansen et al (1979).

Effects of water supply Effects of water withdrawal Effects of sediment supply Effects of sediment withdrawal Effects of giving more space to the flow Effects of giving less space to the flow Effects of weir construction Effects of weir removal