Assessment of post-wildfire erosion risk and effects on water quality in south-western Australia

Abstract

Investigations of wildfire impact on water resources have escalated globally over the last decade owing to an awareness of climate-related vulnerabilities. Within Australia, research into post-wildfire erosion has focused on water supply catchments in the south-eastern region. Here, we examine post-wildfire erosion risk and its potential for water quality impacts in a catchment in south-western Australia. The catchment of the Harvey River, which drains from forested escarpments onto an agricultural coastal plain and into valuable coastal wetlands, was burnt by wildfire in 2016. The aims of this study were to determine erosion risk across contrasting landforms and variable fire severity, using the Revised Universal Soil Loss Equation (RUSLE), and to determine whether post-fire water quality impacts could be detected at permanent river monitoring stations located on the coastal plain. RUSLE outputs showed erosion hot-spots at intersections of steep terrain and high fire severity and that these areas were confined to forested headwaters and coastal dunes. Monthly water quality data showed conspicuous seasonal patterns, but that sampling frequency was temporally too coarse to pick up predicted event-related effects, particularly given that the pre-existing monitoring sites were distal to the predicted zone of contamination.

Cascading Hazards in the Aftermath of Australia's 2019/2020 Black Summer Wildfires

“…The estimated postfire soil erosion rates range from 11‐27 t h −1 y −1 (Table S1), reflecting an increase of over 200%. The absolute values and relative changes are consistent with field measurements from severely burned catchments in NSW (Atkinson, 2012; Blake et al., 2020; Shakesby & Doerr, 2006). The increases in estimated soil erosion in the three tributaries range from 88% in the Gloucester catchment to 358% in the Nowendoc catchment (Figure S3 and Table S1).…”

“…We apply the RUSLE model (Kinnel, 2010;Renard et al, 1991) to estimate first order the pre and postfire soil erosion rates within the Manning River catchment based on rainfall erosivity, soil erodibility, steepness, land cover and management, using input parameters from preexisting datasets (Yang et al, 2015(Yang et al, , 2018 (see supplements). The dNBR burn severity is included by adjusting the postfire land cover-factor accordingly (Blake et al, 2020;Larsen & MacDonald, 2007) based on satellite data from February 2019 and 2020. The estimated postfire soil erosion rates range from 11-27 t h −1 y −1 (Table S1), reflecting an increase of over 200%.…”

Mitigating Source Water Risks with Improved Wildfire Containment

“…First, the linked fire and erosion model system (Figure 1) is subject to multiple data, model, and model linkage uncertainties that have potential for prediction error as discussed extensively in previous publications [24,25]. Recent work has shown that water quality at the basin scale is sometimes minimally impacted despite modeled increases in hillslope erosion [82], emphasizing the need to test and refine erosion and sediment transport models with empirical observations at multiple scales [83]. Most of our predicted first-year post-fire hillslope erosion yields for the 2-year and 10-year rainfall erosivity scenarios (Table 2) are close to the study-wide means of 9.5-22.2 Mg ha −1 and the range of individual hillslope observations of 0.1-38.2 Mg ha −1 from previous fires in the region exposed to moderate rainfall [11,17,47,84].…”

Wildfire Susceptibility Mapping Using Five Boosting Machine Learning Algorithms: The Case Study of the Mediterranean Region of Turkey

“…Research reveals that anthropogenic factors [4,5] and climate change [6][7][8] play a critical role in the frequency of wildfre occurrence and increase in afected areas. Wildfres are not only responsible for the mass destruction of forests but they also have several adverse efects on the natural environment, such as increased erosion risk [9][10][11][12], poor water quality [9], changes in land use [13], and elimination of wildlife [14]. Nevertheless, many Mediterranean plant species have evolved some form of adaptation mechanism for survival in a fre [15].…”