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Table 4 Morphologic indicators for channel changes and their meaning

From: Influence of 200 years of water resource management on a typical central European river. Does industrialization straighten a river?

Indicator Description Meaning
Change in total river length Total river length of the Rur River in a focus region compared to today’s river length, estimated from the DOP 2019 Decrease in the river length is a sign for artificial straightening [87]
Sinuosity Total river length of the Rur River in a focus region divided by the thalweg [88,89,90,91,92], computed with the DEM 25 Reduced sinuosity often is a sign for river straightening [54, 93], an increase is a sign for tending towards a new equilibrium [87] but can also occur when the flow velocity increases [55]
Relative length of channel structures Total length of channel structures in a focus region divided by the river length in the focus region An increase in the channel structures is a reaction to changes in the sediment load and/or changes in the river slope [87], often due to straightening [94]
Anastomosing channel For anastomosing channels Anabranching rivers are often caused by flood-dominated flow regimes [63, 83]
Braided channel For braided river structures in single channels Sign for excess bedload, coarse bottom substrate and high valley bottom slope [57, 95], instable state [96]
Side arm For side arms Occur at flood events as a reaction to hydraulic stress; today side arms are preserved as habitats [97]
Relative of number oxbows Number of oxbows in a focus region divided by the river length in km Oxbows as channel cut-offs are a sign for river course shortening [55]
Relative number of islands Number of islands in a focus region divided by the river length in km Changes in islands indicate recent flood events, island formation is a sign for coarse sediment input [55]
  1. DEM25 digital elevation model with a grid resolution of 25 m, DOP digital orthophoto
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