| 19 Feb 2026
Spatially variable wildfire impacts on sediment mobilization: event-scale evidence from eastern Australian catchments
Abstract. Wildfires may profoundly affect forested catchments by altering hydrological processes, soil properties, and sediment dynamics. While post-fire increases in water quality constituents are well documented, the underlying divers for such changes remain poorly understood. This study examines how fire and short-term hydrologic conditions interact to shape sediment dynamics using a novel Bayesian Hierarchical modelling framework. The analysis is at event-scale based on multi-year, high-frequency turbidity and streamflow data collected from 14 forested catchments in eastern Australia, which were burned to varying severities during the 2019/2020 Black Summer fires and affected by subsequent floods. Further, we explored how these effects vary across catchments with the extent of burning and other catchment characteristics.
Model results show that severe burning had a clear steepening effect on the slopes of event concentration-discharge (C-Q) in 5 out of the 10 severely burnt catchments studied, indicating enhanced sediment mobilization following extreme burning. The influence of short-term hydrologic conditions on C-Q slopes was comparatively minor, suggesting that fire effects dominated post-disturbance sediment responses. The magnitude of fire effects (as post-fire changes in the C-Q slopes) did not always scale directly with the proportion of catchment burnt, which also seems to be driven by the location of extreme burning and forest types. These findings provide a large-scale, multi-catchment understanding of post-fire sediment mobilization mechanisms, which can inform future improvement of modelling and management of sediment in fire-affected forested landscapes.
The manuscript titled “Spatially variable wildfire impacts on sediment mobilization: event-scale evidence from eastern Australian catchments” studies the impact of the fire on C-Q slope and hypnotize that the extreme burning and recent hydro-climatic conditions drive the sediment mobilization in recently burned watersheds. It is an interesting study and the authors have a valuable post-fire dataset. After reading it, however, I think the manuscript requires substantial revision between it can be accepted for publication. The main concerns are presented below, followed by detailed comments. I hope this revision will help guide a stronger analysis.
C-Q analysis – methodology used: The C-Q analysis, in particular on the selection of slope as explanatory variable, would benefit a more detailed methodological justification. Hysteresis index and flushing index are standard metrics used to compare C-Q relationships across sites and studies. The manuscript currently focuses on the slope of the relationship, but this choice is not clearly explained. The authors should justify why the slope is important and which are the mechanisms that could create a change, or they should consider adopting hysteresis and flushing indexes to facilitate comparison with the literature. The authors can Jing et al. (2024) (https:// doi.org/10.1029/2024WR037216) for reference.
Fire severity – soil burn severity: Fire severity (or soil burn severity) measures the magnitude of the impacts of fires on vegetation (and soil). Fire severity is easily obtained by remote sensing images, while soil burn severity needs in situ measurements. The threshold the authors use (0.1% extreme burn), which seems a very low threshold. They use Rhoades et al. (2011) and Marcotte (2024) which don’t mention this threshold in their study. I suggest using fire severity – in particular percentage of high severity – as a variable.
Results: The results section is currently confusing and should be reorganized. In addition, the authors make several interpretative claims (a variable “increase” or “play a critical role”) without presenting statistical evidence. A form of statistical analysis is necessary to support those statements. The authors should conduct appropriate statistical tests and clearly present the results, acknowledging any limitations of the approach.
Discussion: The discussion is currently short and presents only a handful of references. The authors should expand the discussion and interpret their findings with the existing literature on post-fire impacts on sediment yield, water balance, and C-Q dynamics (right now they are citing only three references). The Discussion should also address what the results reveal about the hydrological and erosion consequences of fire, how these compare with findings from similar catchments internationally, and what mechanistic explanations can be offered.
Specific comments: