épandage des eaux de ruissellement

CONT: Irrigation de surface. [...] L'épandage des eaux de ruissellement ou de crue, qui du fait de la brutalité des précipitations, coulent de façon très temporaire dans les régions à faible pluviosité annuelle, est une forme fruste de submersion, utilisée par l'homme depuis longtemps, dans la vallée du Nil ou la Mésopotamie par exemple.

CONT: There are bound to be rainstorms whose water the soil cannot fully absorb - a point of major importance in arid and semi-arid areas, for this water can be collected and used to improve productivity locally. The following four water management methods and erosion control structures apply: . runoff harvesting (catching runoff for supplementary irrigation); . total absorption or infiltration; . runoff diversion (redirecting excess water); . runoff spreading (distribution of runoff energy). ... Structures to dissipate runoff energy. When rainfall exceeds the soil's absorption capacity, the sheet runoff can be controlled by spreading it across the whole slope rather than concentrating it in channels and outlets, where it can cause problems. Its energy can be dispersed by keeping the speed below 25 cm ... Such dispersion across the slope is achieved partly by cropping techniques that keep the soil surface rough (clods, many grass stalks, effect of weeds and mulching, etc.) and partly by structures such as permeable microdams, which temporarily slow the flow, allow some sedimentation, spread the flood, reduce peak flows and improve absorption.