Incorporating spatially heterogeneous infiltration capacity into hydrologic models with applications for simulating post‐wildfire debris flow initiation. Issue 9 (6th April 2018)

• Record Type: Journal Article
• Authors: McGuire, Luke A.; Rengers, Francis K.; Kean, Jason W.; Staley, Dennis M.; Mirus, Benjamin B.
• Is Part Of: Hydrological processes. Volume 32:Issue 9(2018)
• Page Start: 1173
• Page End: 1187
• Publication Date: 2018-04-06
• Subjects: debris flows -- hydraulic conductivity -- infiltration capacity -- run‐off -- wildfire; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.11458
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: Soils in post‐wildfire environments are often characterized by a low infiltration capacity with a high degree of spatial heterogeneity relative to unburned areas. Debris flows are frequently initiated by run‐off in recently burned steeplands, making it critical to develop and test methods for incorporating spatial variability in infiltration capacity into hydrologic models. We use Monte Carlo simulations of run‐off generation over a soil with a spatially heterogenous saturated hydraulic conductivity ( K s ) to derive an expression for an aerially averaged saturated hydraulic conductivity ( K e * ) that depends on the rainfall rate, the statistical properties of K s, and the spatial correlation length scale associated with K s . The proposed method for determining K e * is tested by simulating run‐off on synthetic topography over a wide range of spatial scales. Results provide a simplified expression for an effective saturated hydraulic conductivity that can be used to relate a distribution of small‐scale K s measurements to infiltration and run‐off generation over larger spatial scales. Finally, we use a hydrologic model based on K e * to simulate run‐off and debris flow initiation at a recently burned catchment in the Santa Ana Mountains, CA, USA, and compare results to those obtained using an infiltration model based on the Soil Conservation Service Curve Number.