Effective Green and Ampt parameters for two layered soils
Green-Ampt method is a physically based model for partitioning rainfall into surface runoff and infiltration. This method is widely used in infiltration practice because of its simplicity and the ease of obtaining required hydraulic soil properties. The method assumes that soil is homogeneous, therefore it is difficult to apply to layered soils. In this paper, simple procedures for applying Green-Ampt method to layered soils are examined both under steady and unsteady rain. For a given design storm, the maximum saturated depth of the top layer can be estimated. Because the uppermost layer controls the behavior until the wetting front reaches the boundary of the layers, if the thickness of the top layer is greater than maximum saturated depth, considering only the uppermost layer makes no difference in terms of infiltration process. However, if this is not the case, the bottom layer should be considered. To consider two-layered soils, overall effective Green-Ampt parameters of layered soils are estimated considering different parameters such as rainfall characteristics, the hydraulic properties of both layers, the thickness of the top layer and the maximum saturated depth. Runoff and infiltrated volumes with effective Green-Ampt parameters were compared with MIKE SHE simulation results based on Richards equation for different layer thicknesses, soil properties, and rainfall hyetographs. These results show that the proposed simple and quick procedures for estimating effective soil parameters show good agreement in terms of the volume of runoff and infiltration water. Therefore, this approach will help researchers and engineers to save time and effort dealing with layered soils using Green-Ampt method.
Infiltration into layered soils, Effective Green-Ampt parameters
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign