Effects of wildfire on catchment runoff response: a modelling approach to detect changes in snow-dominated forested catchments

Abstract

Wildfire is an important disturbance affecting hydrological processes through alteration of vegetation cover and soil characteristics. The effects of fire on hydrological systems at the catchment scale are not well known, largely because site specific data from both before and after wildfire are rare. In this study a modelling approach was employed for change detection analyses of one such dataset to quantify effects of wildfire on catchment hydrology. Data from the Entiat Experimental Forest (Washington State, US) were used, a conceptual runoff model was applied for pre-and post-fire periods and changes were analyzed in three different ways: reconstruction of runoff series, comparison of model parameters and comparison of simulations using parameter sets calibrated to the two different periods. On average, observed post-fire peak flows were 120% higher than those modelled based on pre-fire conditions. For the post-fire period, parameter values for the snow routine indicated deeper snow packs and earlier and more rapid snowmelt.The net effect of the changes in all parameters was largely increased post-fire peak flows.Overall, the analyses show that change detection modelling provides a viable alternative to the paired-watershed approach for analyzing wildfire disturbance effects on runoff dynamics and supports discussions on changes in hydrological processes.

Effects of wildfires on peak discharges in watersheds

“…For this reason, the unit-area peak discharge is considered to be the most sensitive parameter for the description of the modified watershed response after a wildfire (e.g., Rowe et al 1954). More specifically, experimental analyses conducted both in Europe and in the United States indicate that the annual peak discharge in postfire conditions can increase by a factor generally ranging from 1.2 to 6.5 (Hoyt & Troxell 1934, Anderson 1976, Hessling 1999, Loáiciga et al 2001, Conedera et al 2003, Rulli & Rosso 2007, Pierson et al 2008, Seibert et al 2010 and can even exceed 100 in some cases (Campbell et al 1977, Bolin & Ward 1987, Neary et al 2003. However, there have been some case studies (Britton 1991, Aronica et al 2002, Bart & Hope 2010 in which little or no increase in postfire discharges were observed.…”

Glacier change and contribution to streamflow in the Canoe Basin, British Columbia, 1948-2005.

“…Generally, decreased vegetation cover in a watershed leads to both higher peak flows (e.g. Scott, 1993;Seibert et al, 2010) Although 'glacier contribution to streamflow' may be a more accurate indicator of glacier change in a watershed, researchers must understand how the metric was achieved or calculated, and the resulting implications on conclusions drawn from the data. For example,…”

Evaluation of short-term changes of hydrological response in mountainous basins of the Vitim Plateau (Russia) after forest fires based on data analysis and hydrological modelling

“…Though hydrological models may be applied to detect the transformation of flow characteristics due to climate or landscape changes (ex., Seibert et al, 2010), future projections of hydrological behavior in non-stationary conditions based on the results of hydrological modelling are generally questionable (Semenova and Beven, 2015). This is because calibration of model parameters has become almost inevitable and rarely challenged part of modelling procedure.…”