Figure 1 Ship passages analysis at the level of the longitudinal dam
navigability, while at high water, the water flows away easily, enhancing flood safety. In addition, the river ecosystem is expected to benefit greatly from a side channel being established for recreation and nature development. The final evaluation of this pilot project was carried out by Deltares.
The main question addressed by MARIN is to what extent the constructed LTDs have an influence on the behaviour of ships. To answer this, AIS data was analysed to compare navigational behaviour at the level of the LTDs section with the upstream and downstream sections of these longitudinal dams.
In total, a 67-kilometre river section was analysed by drawing a virtual passage line on every kilometre (see Figure 1). The number of ship passages per ship type and direction in one year is shown as a stacked bar chart, together with the ships’ contours and the use of space. Other influencing factors such as the river discharge and ship’s loading condition were also included.
Based on the analysis, although the presence of LTDs reduced the available width of the fairway, the dams do not lead to significantly different navigational behaviour. This can be seen from the plot of the average speed profile along the three river sections in Figure 2. Furthermore, the analysis of the use of space shows that the percentage of the river width used is comparable with other sections (see Figure 3).
These findings together with other aspects, such as morphology, nature, social aspects, maintenance, flood safety and freshwater supply will serve as a basis when considering the possible future realisation of other longitudinal dams in Dutch rivers.
Figure 2 Average speed profile during different water discharge conditions
Figure 3 Normalised river width use during different water discharge conditions report 27
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