Observed and simulated hydrologic response for a first‐order catchment during extreme rainfall 3 years after wildfire disturbance

Abstract

Hydrologic response to extreme rainfall in disturbed landscapes is poorly understood because of the paucity of measurements. A unique opportunity presented itself when extreme rainfall in September 2013 fell on a headwater catchment (i.e., <1 ha) in Colorado, USA that had previously been burned by a wildfire in 2010. We compared measurements of soil‐hydraulic properties, soil saturation from subsurface sensors, and estimated peak runoff during the extreme rainfall with numerical simulations of runoff generation and subsurface hydrologic response during this event. The simulations were used to explore differences in runoff generation between the wildfire‐affected headwater catchment, a simulated unburned case, and for uniform versus spatially variable parameterizations of soil‐hydraulic properties that affect infiltration and runoff generation in burned landscapes. Despite 3 years of elapsed time since the 2010 wildfire, observations and simulations pointed to substantial surface runoff generation in the wildfire‐affected headwater catchment by the infiltration‐excess mechanism while no surface runoff was generated in the unburned case. The surface runoff generation was the result of incomplete recovery of soil‐hydraulic properties in the burned area, suggesting recovery takes longer than 3 years. Moreover, spatially variable soil‐hydraulic property parameterizations produced longer duration but lower peak‐flow infiltration‐excess runoff, compared to uniform parameterization, which may have important hillslope sediment export and geomorphologic implications during long duration, extreme rainfall. The majority of the simulated surface runoff in the spatially variable cases came from connected near‐channel contributing areas, which was a substantially smaller contributing area than the uniform simulations.

Progress in simplifying hydrologic model parameterization for broad applications to post‐wildfire flooding and debris‐flow hazards

“…However, in areas with patchy burn severity, an approach that considers infiltration variability may be preferable (e.g., Ebel et al. , ; McGuire et al. , ).…”

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

“…Previous studies have arrived at mixed conclusions regarding the importance of correlation length on run‐off response. Corradini et al () found that variations in correlation length had only a minimal effect on simulated run‐off hydrographs, whereas field‐based investigations and other modeling studies suggest that soil patches with low‐infiltration rates can substantially alter the run‐off response (Ebel et al, (); Sheridan et al, ()). The use of could provide an efficient framework for determining the portion of the parameter space where correlation length plays an important role in the basin‐scale run‐off response.…”

“…Being able to condense information about a spatially variable K s field into a single value of K e that characterizes the run-off response at the basin scale would be valuable for rapid integration of field measurements into simplified hydrologic models and for debris flow hazard assessment purposes. Relationships between K e and K s also help to bridge the gap between hydrologic studies conducted at different scales, such as those that effectively constrain K e through postevent model calibration at the basin scale (e.g., Langhans et al, (2016); Rengers, McGuire, Kean, Staley, & Hobley, (2016)) and those that quantify K s through small-scale field measurements (e.g., Ebel, Rengers, & Tucker, (2016); Langhans et al, (2016)).…”

Meta‐analysis of field‐saturated hydraulic conductivity recovery following wildland fire: Applications for hydrologic model parameterization and resilience assessment

“…Few efforts have measured or estimated K fs recovery for more than 3 years after wildfire, belying the importance of K fs for numerical modelling of hydrologic recovery and associated water-related hazards at the plot-scale (e.g., Ebel, 2013) and watershed scale (Cydzik & Hogue, 2009;Ebel, Rengers, & Tucker, 2016;Rengers, McGuire, Kean, Staley, & Hobley, 2016). Here, we have reviewed the literature and isolated the studies that investigated the recovery of K fs for more than 3 years following wildfire, which are summarized in Table 2.…”