Incorporating spatially heterogeneous infiltration capacity into hydrologic models with applications for simulating post-wildfire debris flow initiation

5 years ago

Incorporating spatially heterogeneous infiltration capacity into hydrologic models with applications for simulating post-wildfire debris flow initiation

Benjamin B. Mirus, Dennis M. Staley, Jason W. Kean, Francis K. Renger, Luke A. McGuire

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 runoff in recently burned steeplands, making itcritical to develop and test methods for incorporating spatial variability in infiltration capacity into hydrologic models. We use Monte Carlo simulations of runoff generation over a soil with a spatially heterogenous saturated hydraulic conductivity(Ks) to derive an expression for an aerially averaged saturated hydraulic conductivity ( Ke*) that depends on the rainfall rate, the statistical properties of Ks, and the spatial correlation length scale associated with Ks. The proposed method for determining Ke* is tested by simulating runoff 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 Ks measurements to infiltration and runoff generation over larger spatial scales. Finally, we use a hydrologic model based on Ke* to simulate runoff and debris flow initiation at a recently burned catchment in 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.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/hyp.11458