Flood protection and monitoring in Germany: Rees retention basin
Close cooperation of AFRY’s environmental and water experts on behalf of the Waterways and Shipping Authority (WSV)
At the Rees-bend of the Rhine, elevated water levels repeatedly carried away large amounts of gravel, sand and rock debris, which deposited in unwanted locations-with consequences for navigation and riverside structures. To counteract this, the Flood Basin Rees was constructed.
In the past, erosions and depositions at the Rees Bend had caused problems for shipping and riverside construction despite repeated remedial measures. In order to sustainably address this, the Flood Basin Rees was built between 2009 and 2015 on the left-bank foreland between Rhine km 833.5 and 839.0. It provides a larger discharge cross-section when water levels rise above mean water, thereby reducing erosion, alleviating load on the city wall of Rees, and stabilizing the groundwater level.
From 2009 to 2016, a construction-accompanying monitoring program of biotic and abiotic factors was carried out on behalf of the Waterways and Shipping Authority (WSA) Duisburg Rhine. The surveys were aimed in particular at determining the degree of target attainment of the compensation measures stipulated in the project approvals. Seven status reports on the condition of the Flood Basin were compiled and published.
In 2018, a maintenance plan for the Rees flood channel was also drawn up. This plan established quality standards for considering ecological aspects during the maintenance of the flood channel.
AFRY carried out the construction monitoring from 2009 to 2016 at our Cologne location in Germany. The maintenance and upkeep plan was also prepared by the AFRY Cologne team.
The WSA Rhine has commissioned further biotic and abiotic monitoring from 2025 to 2032. Within the framework of this monitoring, the degree of target attainment of the individual measures implemented will again be recorded, and an overall project success review conducted. In addition, concepts will be developed to ensure the long-term functionality of the flood basin and ferry cut-through, as well as the target biotopes.
AFRY has also been appointed for these services. Cross-location environmental and water experts are working closely together for this task.
Our services include:
• Retrieval, checking and analysis of hydrological and hydro-morphological data
• Analysis of water level conditions, flows and discharge in the Rhine and in the flood basin
• Investigation of the groundwater level at six measuring points
• Evaluation of pond water levels including interactions between pond level and small water bodies in the nature reserve
• Analysis of the two accumulation zones – ferry cut-through and inlet threshold – in conjunction with findings from sedimentological, morphological and hydraulic investigations
• Conducting biotope-type mapping and vegetation surveys according to Braun-Blanquet
• Avifaunistic surveys (breeding birds, resting birds and winter guests)
• Macro-zoobenthos investigations
• Amphibian investigations
• Butterfly and dragonfly investigations
• Bat investigations
• If sufficient indications exist, also macrophyte populations and reptiles
