Sediment redistribution following wildfire in the Sydney region, Australia: a mineral magnetic tracing approach

Increased sediment and nutrient fluxes arising after wildfires may affect downstream water quality. We use mineral magnetic tracers to elucidate linkage between different slope units, river channel and a reservoir sediment column in the gorge-dissected landscape of a burnt water supply basin. Comparison of magnetic properties of source areas with downstream (sub-aerially stored) channel deposits Suggests predominantly ridge-top origin with significant storage of sediment within footslopes. Magnetic properties of the sediment column provide insight into the nature of sediment accumulation on the reservoir floor and the role of immediate post-fire rainfall events. Comparison of source signatures with sub-aqueously stored sediment is complicated by the apparent fragility of some fine pyrogenic mineral grains; these may have to be accounted for in sediment column interpretation. Tracing tools provide river basin managers with important process-based evidence of post-fire sediment redistribution, useful for more effective mitigation of these infrequent, but significant, sediment redistribution events.