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Design of pressure-relief wells at the dyke fortification of the Lek River in the Netherlands

The river Lek flows through Schoonhoven in the Big River Region of the Netherlands. The water level of the river is on average higher than the surrounding polder landscape, which has to be artificially drained to allow for agriculture and habitation. River dykes serve to protect the hinterland from long-duration high water waves on the Lek river, with a return period of 2000 years. During a high water event, the water pressure under the dyke increases due to the high water level in the river. This pressure lowers the geotechnical stability of the dyke, with possible risks for collapse.To relief this pressure, AGT designed a groundwater model to simulate the effects of wells on the passive release of groundwater to the polder drainage. A field campaign with double pumping tests was conducted to improve the groundwater model parameters. The well discharges and water levels were calculated in order to safeguard the dyke and its hinterland.