Effects of Slope, Compaction, Gravel Mulch, and Landscape Fabric on Infiltration for Sandy Soils

In arid and semiarid regions, urbanization is associated with land-use changes, including soil compaction and changes to surface slopes, as well as the application of gravel mulch and landscape fabric typical of desert landscaping. These changes affect runoff and infiltration dynamics in dryland watersheds. Planning and design of drainage infrastructure requires hydrologic models that can predict the runoff response of anticipated future land-use conditions. Reliable guidance for parameterization of infiltration models is therefore crucial. In this study, we use rainfall simulation to investigate the individual and combined effects of compaction, slope, and gravel mulch on runoff and infiltration from test plots with sandy soils. We compare findings with previous studies for natural plots with varying vegetative cover. Results showed that the slope had a minimal effect on infiltration. On bare soils, infiltration was similar for uncompacted and compacted conditions, likely due to the formation of a physical crust. On average, uncompacted soils with gravel mulch resulted in 78% higher infiltration compared with bare soils, likely due to the prevention of crust formation. The addition of landscape fabric led to a 12% decrease in infiltration on uncompacted soils compared with gravel mulch alone. Findings were used to develop reasonable parameter ranges for three infiltration models available in the widely used Hydrologic Engineering Center–Hydrologic Modeling System (HEC-HMS). This new guidance can be used to parameterize infiltration models and inform design decisions in urbanizing arid and semiarid landscapes.