The Chalk Aquifers of Northern Europe
CONTAINS OPEN ACCESS
The Cretaceous Chalk aquifers of Northern Europe underlie and support many sensitive ecosystems whilst at the same time being an important source of drinking water. This volume brings together the outcomes of numerous projects and case studies to provide the latest applied and theoretical understanding of all aspects of Chalk hydrogeology in Northern Europe.
Example of a sinkhole landscaping project within the close protection area of a drinking water catchment at Saffré (France, Loire-Atlantique)
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Published:September 07, 2023
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CiteCitation
Paul-Henri Mondain, 2023. "Example of a sinkhole landscaping project within the close protection area of a drinking water catchment at Saffré (France, Loire-Atlantique)", The Chalk Aquifers of Northern Europe, R. P. Farrell, N. Massei, A. E. Foley, P. R. Howlett, L. J. West
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Abstract
The frequent sinkholes along the temporary water streams in Saffré basin can be compared with those occurring in Upper Normandy which are commonly referred to as ‘bétoires’. These collapses are not directly linked to karst cavities. They result from a draw-off effect of fine particles contained in the Plio-Quaternary alluvium lying above the carbonate Oligocene series. The draw-off phenomenon appears through fine cracks (1 to a few millimetres) open in soft palustrine limestones broadly comparable with chalk. Based on the knowledge of backfilling work design undertaken at some ‘bétoires’ in Upper Normandy, a new project was undertaken at four sinkhole funnels, which appeared near the surface in the Saffré basin at the end of the winter in 2017. The works consisted of digging the decompressed surface and filling up the excavation pit with materials of decreasing granulometry from bottom to top in order to ease the surface water infiltration through the identified fractured zones to the bottom of the excavation. This design was also complemented by the implementation of a filtering trench in between the watercourse and the filtering bed, laid above the fractured zones, which were enlarged by the dissolution process, on the one hand, and by the construction of a pipe network on top of the filtering bed to allow for pressurized air exhaust towards the surface, on the other hand. The pressurized air comes up from the aquifer as it recharges as soon as the surface water streamflow resumes and takes part in the mechanism, leading to sinkhole collapse, which should be prevented by this backfilling design.
- alluvium aquifers
- aquifers
- carbonate rocks
- chalk
- Cretaceous
- drinking water
- Europe
- failures
- fractures
- France
- granulometry
- ground water
- hydrographs
- infiltration
- limestone
- Loire-Atlantique France
- Mesozoic
- Normandy
- sedimentary rocks
- sinkholes
- solution
- solution features
- springs
- surface water
- water wells
- Western Europe
- betoires
- Saffre France
- Isac River