Building up the 1D-model

For the middle part of river R a 1D-model was deployed based on the digital terrain model. GIS created this digital terrain model by using the survey data. 143 cross sections were extracted from the digital terrain model.

For each cross section the roughness and vegetation parameters were allocated based on the inspection on location. The soil material in the riverbed varies from sand to gravel. In several sections the bank and the riverbed is characterised by embankments, which prevent a scour of bed material during weak and medium flood events. These bed structures function as a pavement against hydraulic influences

Table 1: Equivalent sand-roughness ks

On flood plains the vegetation varies between small, medium and high vegetation. The parameter of equivalent sand-roughness ks only includes the natural cover of small plants. Distance and delimiter parameterise high types of vegetations, as single roughness elements. The distances and delimiters shown in table 2 have been determined during the inspection on location.

In the following subchapters it is described how the equivalent sand-roughness ks and the roughness of small, medium and high vegetation is determined.

Table 2: Distances and delimiters for small, medium and high vegetation

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