Can pore-clogging by ash explain post-fire runoff?

International Journal of Wildland Fire
By: , and 



Ash plays an important role in controlling runoff and erosion processes after wildfire and has frequently been hypothesised to clog soil pores and reduce infiltration. Yet evidence for clogging is incomplete, as research has focussed on identifying the presence of ash in soil; the actual flow processes remain unknown. We conducted laboratory infiltration experiments coupled with microscope observations in pure sands, saturated hydraulic conductivity analysis, and interaction energy calculations, to test whether ash can clog pores (i.e. block pores such that infiltration is hampered and ponding occurs). Although results confirmed previous observations of ash washing into pores, clogging was not observed in the pure sands tested, nor were conditions found for which this does occur. Clogging by means of strong attachment of ash to sand was deemed unlikely given the negative surface charge of the two materials. Ponding due to washing in of ash was also considered improbable given the high saturated conductivity of pure ash and ash–sand mixtures. This first mechanistic step towards analysing ash transport and attachment processes in field soils therefore suggests that pore clogging by ash is unlikely to occur in sands. Discussion is provided on other mechanisms by which ash can affect post-fire hydrology.

Publication type Article
Publication Subtype Journal Article
Title Can pore-clogging by ash explain post-fire runoff?
Series title International Journal of Wildland Fire
DOI 10.1071/WF15037
Volume 25
Issue 3
Year Published 2016
Language English
Publisher Fire Research Institute
Publisher location Roslyn, WA
Contributing office(s) National Research Program - Central Branch
Description 22 p.
First page 294
Last page 305
Online Only (Y/N) N
Additional Online Files (Y/N) N
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