Assessing the Impacts of Wildfire on Sedimentation and Runoff in the Colorado Front Range
The complex effects of wildfire disturbances on the quality and availability of water are far-reaching and often difficult to anticipate, thus proving a challenge for prediction. Many studies have documented wildfire on either continental or hillslope scales, yet most critically overlook the interaction of local-scale processes across entire watersheds following a fire disturbance. In this study, we explore modifications to a hydrologic model to portray the effects of wildfire disturbance at the basin scale on streamflow and suspended sediment loading (SSL) in a disturbed, mid-sized (approx. 1,056 mi2) watershed on the Colorado Front Range. The Variable Infiltration Capacity (VIC) model, a semi-distributed hydrologic model that solves land surface-atmosphere exchanges of moisture and energy, was upgraded to include five hillslope erosion algorithms in order to quantify uncertainties in SSL estimation under a unified framework. Wildfire disturbance is simulated through modification of soil and vegetation characteristics based on a diverse set of historical in-situ and remotely sensed observations of basin features that become perturbed following a wildfire event, using the 2012 High Park Wildfire in the Cache La Poudre basin as a case study. One such feature is Leaf Area Index (LAI), a characterization of the plant canopy, as observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. Model parametric modifications are optimized with multiple objectives to evaluate the robustness of simulated sediment loading and runoff in the immediate aftermath of a wildfire. The results from this study have implications for water management and reservoir operations in the West.