Abstract
The understanding of unsaturated flow in heterogeneous formations is a prerequisite to the understanding of pollutant transfer in the vadose zone and the proper management of infiltration basins settled over such heterogeneous formations. This study addresses the effect of lithological heterogeneity of a glaciofluvial deposit on flow in the vadose zone underneath an infiltration basin settled in the Lyon suburbs. The basin had already been the subject of several previous studies, some of which demonstrated the impact of soil heterogeneity. But all of them were only based on the sedimentological study of a trench and no study addressed the potential spatial variability of results due to the spatial variability of soil heterogeneity. In this study, we model flow in the vadose zone for several case studies, including drainage, water infiltration during a rainfall event, and a complete meteorological chronic. These calculations were conducted for several sections, previously characterized in the basin using GPR and sedimentological study and compared with a blank (homogeneous section). The results clearly show that heterogeneity impacts unsaturated flow and that these impacts depend upon the section considered. Some geometrical architectural and textural parameters were proposed to explain the spatial variability and effect of the soil heterogeneity on unsaturated flow, thus establishing the first step towards modeling unsaturated flow in the basin at the meso-scale.
Highlights
Nowadays cities expand as a result of urbanization
We have scanned the ground with Ground penetrating radar (GPR) over several sections and we have modeled the flow in these different sections and compared the results with the flow in a homogeneous section containing the main material
We examined the effect of soil heterogeneity on unsaturated flow processes
Summary
The extension of urbanization and sealed surface results in the modification of the water cycle, and the volumes produced by the sealed surface are too important to be collected and treated in usual stormwater plants. To alleviate such problems, best management practices have been developed, most of which are based on the infiltration of runoff water in infiltration basins or pits. A particular care must be taken about the pollutants carried by runoff water (heavy metals, organics, etc.) that can be responsible for the degradation of the quality of the soils
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