Reused gravel fill from the Rhine for ecological enhancement of riparian areas, stabilization of existing riparian structures, and protection from bank erosion.
In the bank area of the Rhine between the Black Forest Bridge and the Wettstein Bridge, the Rhine gravel obtained from the ancillary project "Correction of the Navigation Channel" is to be reused in the form of gravel fills. On the one hand, these will enable the ecological upgrading of the riparian areas by creating new spawning grounds and fish habitats. On the other hand, they stabilize the existing bank obstructions and protect them from bank erosion. Initially, securing measures such as groynes and islands were installed and the works pipelines were extended. After filling and coarse modeling, fine modeling and structural measures (sturgeon stones, fascines, cuttings) followed.
The in-water work had to be completed by the end of January 2019 because the fish protection period began. Due to very confined space conditions at the transfer point, high demands were placed on the logistics. The work was carried out using floating equipment and required extensive intermediate transportation over water. The material was delivered just-in-time and a total of 17,700m3 of gravel was placed in 7 sections. In order to prevent loose gravel material from being immediately clogged up again by turbidity and mud, the backfilling work had to be carried out in the direction of flow. In addition, the changing water levels of the Rhine influenced the construction site.
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