The planning room for the Cologne-Worringen retention area is located in the north of the city of Cologne, on the left bank of the Rhine between the districts of Langel, Fühlingen, Blumenberg, Thenhoven, Roggendorf and Worringen. In the northeast and east, the area is delimited by the Rhine main dike. In the southeast, the border is formed by the Hitdorf ferry route, in the south by the state road L43. The border in the west is the high bank on the western edge of the Worringer Bruch near Roggendorf and Thenhoven. In order to improve flood protection on the Lower Rhine to the Netherlands and to reduce the ripples in extreme flood drains in the Rhine, the state of North Rhine-Westphalia is striving to recover former floodplains at several locations by relocating dykes and connecting the floodplains to the flood channels of the Rhine and by building controlled retention areas to cut flood peaks. One of these locations is located in the former Rhine loop of the Worringer Bruch. Due to the importance also for the regional flood protection, the retention area in planning approval section 10 was included in the flood protection concept of the city of Cologne. The retention space is designated on an area of approximately 691 ha. Approximately 70 % of the area is used for agriculture, about 30 % consists of forest areas, mainly in the Altrheinschleife of the FFH area and nature reserve ‘Worringer Bruch’. Only a subordinate part of the land is fortified by roads and paths or is used for settlement purposes. At a maximum level of 43.00 mNN, which corresponds to a Rhine flood of 11.90 mKP with a probability of occurrence of once in about 200 years at Worringen, the volume is about 29.4 million m3. Due to the planned use of the retention area exclusively in the event of flood events that exceed the flood protection target of the up to 11.90 mKP protected districts, the main dike line remains in the currently existing Rhine-near route. The protection of the rear buildings during operation of the retention area is ensured by three-zone dikes, dikes with integrated sheet pile wall, protective walls and a mudguard. East of the former wastewater treatment plant Worringen, a controllable inlet and outlet structure is arranged for flooding and emptying the retention space. Flooding of the retention area is planned at the earliest when a water level of 11.70 mKP is reached, when the official flood forecast predicts a wave crest above 11.90 mKP. The flooding of the retention area takes place with the aim of capping the tip of the flood wave in order to avoid exceeding the rated water level of 11.90 mKP. With a further increase in the Rhine water level, valuable time can be gained for evacuation and safety measures. After the flood section has expired, the retention area is emptied via the inlet and outlet structure in the main dike of the Rhine with the ongoing flood wave in the Rhine up to the height of 39.00 mNN (equivalent to about 8 mKP). The lower areas within the fracture area are emptied via the Pletschbach stream and a pumping station arranged at the B9 before the passage. 1 Rheindeich The main Rhine dike between Worringen and Langel was raised after the flood in 1995 and now offers protection up to a water level of 11.90 meters Cologne level. 2 dikes in the retention area In the southeast as well as in the northwest of the retention area up to 6.50 meter high dikes are planned, partly with integrated sheet pile wall. In the west and southwest, the retention area is mainly limited by the natural height of the terrain. In the low-lying area along the Bruchstraße, a flood protection wall is being erected. The two underpasses under the railway line are kept dry by pumps with emergency power supply. 4 Fangedamm with sewer Along the Brombeergasse a Fangedamm is built. This compact structure requires significantly less space than a dike. 5 Elevation Neusser Landstraße In the north, the Neusser Landstraße is slightly elevated and provided with a flood protection wall up to 1.20 meters high with integrated sheet pile wall. 6 Inlet and outlet structure Through the inlet structure in the dike, up to 330 cubic meters of water per second can flow into the retention space. The structure consists of four flaps, each 6 meters long. It also serves as an outlet structure. 7 Shut-off structures Pletschbach The Pletschbach, which rarely carries water, is closed by two shut-off structures in the event of flooding. 8 Remaining emptying Pletschbach 9 Remaining emptying pumping station The remaining emptying from a water level of less than 8 meters Cologne level takes place via the Pletschbach and the planned pumping station. Lot-by-lot allocation is foreseen as follows: Lot 1: Multi-project control Lot 2: Stakeholder management Lot 3: Project management of overarching services Lot 4: Project control Main component Engineering structures Lot 5: Project management Main component Roads – dikes – terrain modelling Reference is made to the tender specifications.
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