DRAINAGE RETENTION CAPACITY (DREC) TO REDUCE RUNOFF IN DRAINED AREAS (MALINIK FOREST AREA, CZECH REPUBLIC)

摘要

Installing drainage systems in saturated soils decreases the level of the groundwater table and enables the creation of groundwater reservoirs without gravity water, i.e. drainage retention capacity (DREC). DREC, developed by the hydraulic functions of a drainage system, can be defined as a groundwater reservoir, created by the action of a drainage system, which is limited by the soil surface and by the shape of the groundwater level between two parallel neighbouring drains. DREC has the potential to mitigate the negative impact of extreme weather events in the form of floods or rainstorms. The purpose of this paper is (i) to present a methodology for explicit determination of DREC in a period with high-intensity rainfall using the De Zeeuw-Hellinga equation, and (ii) to describe the application of DREC in a design of surface drainage system restoration in an engineering project commissioned by the Ministry of Agriculture of the Czech Republic for water regime protection in the Malinik forest area, Jizera Mountains, Czech Republic. The results, obtained from numerical experiments, show that DREC can reduce surface flow very effectively. In the Malinik forest area, which has a high value of hydraulic conductivity about K= 1.0mday(-1), effective porosity P = 0.075 (-) and drain spacing L = 15m, peak runoff was reduced very significantly by using DREC. Outcomes of surveying that are presented in this paper in mathematical equations, can serve as a reliable tool for immediate DREC approximation, requiring only a minimum amount of fundamental information, i.e. basic soil hydrology data and parameters of the drainage system. Copyright (C) 2016 John Wiley & Sons, Ltd.