Modelling the impact of agri-environmental scenarios on runoff in a cultivated catchment (Normandy, France)

Numerous models have been developed to assess the impacts of land-use modifications. This paper presents a brief description of the remote sensing version of STREAM, called STREAM-TED, which then is used to estimate and map runoff according to various scenarios of rain event and land-use distribution in a cultivated catchment. Three kinds of scenarios of land-use modifications have been considered: partial or complete reduction of grassland in favour of cash crops, modifications of agricultural practices on arable lands, and insertion of water management on the catchment. Results of 11 management scenarios tested showed the negative effect of a partial or complete ploughing of permanent grassland. Changes on arable land scenarios showed that these modifications reduced runoff in various ways according to rainfall events. The scenario with the most significant impact consists of simulating the introduction of 100% more environmentally friendly production methods on arable lands. With this scenario, runoff is practically eliminated for winter rainfall events and is decreased twofold for summer rainfall events. In addition, it is the only scenario which leads to a significant runoff volume reduction even with a “catastrophic” rainfall event.