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Interactions en crue entre drainage souterrain et assainissement agricole

Abstract : The sight of water discharging from underground pipes into open ditches has often prompted suspicions that subsurface drainage is an aggravating contributor to floods. One of the reasons being the perception that water reaches the hydraulic network faster in drained areas compared to un-drained ones, where water pathways (infiltration, surface runoff)are perceived to be more diffuse and harmless. Drainage outlets are also known to discharge many agricultural pollutants within watercourses. Nevertheless, evaluating the actual impacts of subsurface drainage impacts on water quantity and quality remains quite difficult because many processesare involved and interact with each other.One seducing work angle is to evaluate the role played by arterial drainage ditches because the actual water pathways and hydraulics can be rather well known. To improve the lowering of the outfall level of the field drains, collector ditches tend to be deepened and enlarged, which in turn improves their capacity to transfer water and thus contribute to downstream flooding. One possible way to cope with this problem is to slow down flood waves within the arterial drainage network.Subsurface drainage outlets could thus be the site of an interesting retroactive loop : their discharge contributes to floods and pollution, but subsurface drainage efficiency may be reduced by their immersion if the water level is artificially kept high along the ditch.This work attempts to describe more precisely this double effect. It is at first based on experimental data from a field experiment located in the Seine-et-Marne department, 100 km east of Paris, France. During winter flood events, flow rates were monitored within subsurface drainage collector pipes as well as in the adjacent arterial drainage ditch, together with water levels.A second complementary set of experiments were conducted on a laboratory flume, reproducing on a large scale the junction of an open channel and a drainage pipe, supplied with independent flow rates.Explanation and modeling of this particular junction are developed to fit with both laboratory and field experiments. Explanations proposed could be the base for better understanding the behavior of small agricultural catchments equipped with improvedsubsurface drainage.The theoretical research work is followed by a look into the consequences on engineering practices, when dealing with environmental impacts of human activities, or flood risks management. It also contributes to a better knowledge of hydraulic and hydrologic key processes for point source discharging.
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Contributor : Yves NEDELEC Connect in order to contact the contributor
Submitted on : Wednesday, May 4, 2005 - 9:38:37 AM
Last modification on : Monday, June 21, 2021 - 11:34:02 AM
Long-term archiving on: : Friday, April 2, 2010 - 10:07:12 PM


  • HAL Id : tel-00009180, version 1



Yves Nedelec. Interactions en crue entre drainage souterrain et assainissement agricole. Autre. ENGREF (AgroParisTech), 2005. Français. ⟨tel-00009180⟩



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