Assessment of Hillslope Terracing Effects On Vadose Zone Hydrology At Multiple Scales Using Ground-Based Lidar and Electromagnetic Induction.

In the semiarid Western U.S. legal constraints, engineering limitations and competing interests over surface water have encouraged further assessment of surface water hydrology/vadose zone interactions for watershed managers. Correlations between small-scale slope terracing and soil moisture were assessed using ground-based LiDAR and Electromagnetic Induction (EMI). The site is a north facing slope with Palouse silt loam soils continuously grazed throughout the growing season in northern Idaho. A 1cm by 1cm resolution scan was obtained with a green laser Leica Scan Station 2. Through the use of Cyclone and Point-to Grid software, the LiDAR point cloud was rendered into a high resolution digital surface model. Electromagnetic Induction scanning was used to map the electric conductivity within the site to a depth of 1.5 meters both parallel to and perpendicular to the site slope. A map of water content was then generated from these data using soil core samples and analysis at 0-5, 15-20, 30-35, 50-55 and 95-100cm of depth for site-specific calibration. Physical soil samples gathered throughout the site to a depth of 1m provided verification of EMI data. Correlations between LiDAR and EMI data were tested across the slope with respect to terrace morphology. Correlations between terrace presence/absence and soil moisture were also tested. Surface topography gathered by ground-based LiDAR, at smaller scales (1m and 1cm) than flight-based LiDAR (>1m), coupled with seasonal EMI data can provide further insight into our understanding of the spatial and temporal variability of soil moisture on micro-topographic hillslope features. With further detailed parameterizations of surface micro-topographic features and vadose zone hydrology the potential exists to further our understanding of watershed hydrologic yield and retention capacity for watershed modeling, thereby evolving soil and water conservation practices.