Event Title

Session A5: To Reach Good Ecological Quality of Rivers by Dam Removal

Location

Groningen, The Netherlands

Event Website

http://fishpassage.umass.edu/

Start Date

23-6-2015 2:15 PM

End Date

23-6-2015 2:30 PM

Description

Abstract:

Dam removal is currently considered as the best solution for improving the ecological transparency and the sedimentary transparency of rivers. Among other advantages, these operations provide an essential ecosystemic service in terms of water quality. By removing the dam, water retention located upstream is also removed, hence offering the river a current facies that enables its flow, speed, temperature and oxygenation to be improved, in particular via the recovery of the waterway's natural invert function which generates turbulent flow zones propitious to air/water exchange. This river movement recovery also improves its self-purification and, consequently, its resilience, which are factors that improve both its biological quality and its physicochemical quality. As such, in waterways where water quality was stagnant, one can hope to achieve correct conditions as described in the Water Framework Directive. A concrete example of the achievement of correct conditions by the simple additional effect of dam removal is present on the River Orne (Enfernay and Maisons Rouge dams). The spectacular improvement of millstream perpendicular to the zone where the dam was removed would appear to demonstrate the efficiency of this measure with regard to the recovery of superficial water quality. The ecosystemic service offered to the river is evaluated at €3.3M, representing an economy of around €2M compared to a theoretical water treatment solution. In waterways having benefited from intensive clean-up operations in the drainage basin, we can now consider that river delayering via the removal of a significant number of constructions as the sine qua non condition for achieving correct conditions. The quest for a maximum additional layering level of 30% enables the river to recover quality flow over at least 70% of its length can be considered as a preliminary

Comments

Presenting Author Bio: Manager of Normandy unit of l'Agence de l'Eau Seine Normandie/FRANCE, Mr BERNE, Water and Forest General Engineer, is a french specialist of dam removal and hydromorphology improvement. He has erased more than one hundred dams on little rivers of Normandy, which is now one of the the first region in France for migratory fishes ( atlantic salmon, sea trout, lamprey,shad, etc..) and water quality. He pilots the big project of removal of Vezins dam on Selune river, which is the bigest removal in all Europe (33m high, 20km reservoir lake) for the ecological restoration of atlantic salmon of Mount St Michel Bay ( présented in the last NASCO conférence in St MALO/FRANCE). He as written a lot of articles in french or international scientific or juridics journals.

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Jun 23rd, 2:15 PM Jun 23rd, 2:30 PM

Session A5: To Reach Good Ecological Quality of Rivers by Dam Removal

Groningen, The Netherlands

Abstract:

Dam removal is currently considered as the best solution for improving the ecological transparency and the sedimentary transparency of rivers. Among other advantages, these operations provide an essential ecosystemic service in terms of water quality. By removing the dam, water retention located upstream is also removed, hence offering the river a current facies that enables its flow, speed, temperature and oxygenation to be improved, in particular via the recovery of the waterway's natural invert function which generates turbulent flow zones propitious to air/water exchange. This river movement recovery also improves its self-purification and, consequently, its resilience, which are factors that improve both its biological quality and its physicochemical quality. As such, in waterways where water quality was stagnant, one can hope to achieve correct conditions as described in the Water Framework Directive. A concrete example of the achievement of correct conditions by the simple additional effect of dam removal is present on the River Orne (Enfernay and Maisons Rouge dams). The spectacular improvement of millstream perpendicular to the zone where the dam was removed would appear to demonstrate the efficiency of this measure with regard to the recovery of superficial water quality. The ecosystemic service offered to the river is evaluated at €3.3M, representing an economy of around €2M compared to a theoretical water treatment solution. In waterways having benefited from intensive clean-up operations in the drainage basin, we can now consider that river delayering via the removal of a significant number of constructions as the sine qua non condition for achieving correct conditions. The quest for a maximum additional layering level of 30% enables the river to recover quality flow over at least 70% of its length can be considered as a preliminary

https://scholarworks.umass.edu/fishpassage_conference/2015/June23/74