Influence of biopolymer-based topsoil treatments on surface-subsurface hydrological processes: Implications for protection and restoration of sandy slopes

Abstract

Soil protection is critical to the long-term stability and ecology of sandy slopes, wherein the surface–subsurface hydrological processes play a central part. This study investigates the hydrological impacts of a novel hydrophilic polysaccharide biopolymer (HPB) soil modifier on sandy soil, examining its effects on permeability, specific yield, runoff generation, water balance, and soil saturation dynamics. Laboratory tests were conducted to assess the influence of varying HPB concentrations (10 %, 20 %, and 30 %) and curing times (6 h, 12 h, 24 h, and 48 h) on soil hydraulic properties. The integrated surface–subsurface hydrological model, ParFlow, is used to study the controls of topsoil treatment on hydrological processes based on a real-world application example at Xinmeng river, Changzhou region, China. Experimental results indicate that higher HPB concentrations and extended curing times reduce soil permeability and specific yield. Runoff generation patterns are significantly influenced by HPB concentration, with higher concentrations leading to infiltration-excess runoff, while lower concentrations result in saturation-excess runoff. The water balance is controlled by the interplay between rainfall intensity and HPB concentration, with higher concentrations and intensities increasing overland flow and reducing infiltration. Soil saturation profiles are controlled by topsoil treatment, particularly with high HPB concentrations, creating a distinct interface between treated and untreated soils and isolating the subsoil from meteorological influences, which facilitates the ecological restoration of engineering slopes. The study provides decision-making support on the use of HPB for soil treatment in environmental and engineering applications, particularly for the stablization and restoration of sandy slopes.