Surface runoff and erosion after prescribed burning and the effect of different fire regimes in forests and shrublands: a review

This paper examines the state of knowledge about the effects of prescribed burning on surface runoff and erosion at point to catchment scales in forests and shrublands. Fires can increase surface runoff and erosion by removing vegetation, changing soil hydrologic properties and providing a readily erodible layer of sediment and ash. Catchment-scale studies in prescribed-burnt areas usually report minimal impacts from the burn. However, measurements at smaller spatial scales suggest that large changes to hydrologic properties and processes do occur, and a debris-flow example from Australia demonstrates that large catchment-scale impacts are possible. It appears that existing catchment-scale studies in prescribed burns do not capture these large events as the sample size (i.e. number of studies) is too small relative to the infrequency of such events. Furthermore, numerous knowledge gaps across all spatial scales limit understanding of the processes contributing to post-prescribed burn runoff and erosion. Understanding the influence of fire regime characteristics on post-fire runoff and erosion is particularly important in the context of prescribed burning, as fire regimes can be manipulated to reduce erosion and water-quality impacts. Therefore, two directions for future research are recommended: (1) process-based studies to understand the factors controlling surface runoff and erosion, particularly in relation to aspects of the fire regime; and (2) landscape-scale surveys to quantify large erosion events.