Evaluating the Effects of Forest Cover Changes on Sediment Connectivity in a Catchment Affected by Multiple Wildfires

Wildfire-related impacts on the hydrogeomorphic properties of river basins is scarcely studied in South American sites. Fire affects river systems by altering the forest cover, decreasing the soil infiltration capacity, modifying the sediment yields and leading to channel instability. To study the effect of the disturbance in the sediment routing, the analysis of changes in sediment connectivity, i.e. the degree of linkage between source and sink areas, has been recently used. The main aim of the present research is to adapt and apply the Index of Connectivity (IC) in a Chilean catchment affected by subsequent wildfires in 2002 and 2015. Specific objectives involve the derivation of fire severity maps of both wildfires, and the development of a weighting factor, which properly represents the impedance to sediment fluxes. We made use of satellite images and sampling plots to carry out the fire severity maps and then the Normalized Difference Vegetation Index (NDVI) for the computation of the weighting factor maps used in the connectivity analysis. The results demonstrated not only the applicability of this approach, which permitted to highlights the changes in IC patterns but even the predominant changes in forest cover as well as the preferential sources of sediment within the basin.