The role of agricultural drainage networks in the dynamic slowing of floodwaters: interpretation of the Orgeval observatory data

Abstract

The study of the effect of agricultural artificial drainage on catchment outflow has is complex. Predicting the drainage impacts on downstream peak flow involves different scales (spatial and temporal). This work follows up experiments carried out in two drained catchments at Orgeval site. Data observation showed that, during intense rainfall events, the drainage system may flow, temporary, under pressurised condition and the drainage discharge is limited. A frequency analysis of peak discharges based on data at the catchment outlet over 20 years was done. The results showed a peak discharge limitation phase for events with a return period of two and ten years. The pressuriation of the drainage network explains this limitation of peak discharge. Such flow conditions allow for drainage systems a self control of drainage discharge and then avoid the risk of flooding.