Sediment connectivity changes in an Andean catchment affected by volcanic eruption

Lorenzo Martini; Lorenzo Picco; Andrés Iroumé; Marco Cavalli

doi:10.1016/j.scitotenv.2019.07.303

Sediment connectivity changes in an Andean catchment affected by volcanic eruption

Sci Total Environ. 2019 Nov 20:692:1209-1222. doi: 10.1016/j.scitotenv.2019.07.303. Epub 2019 Jul 21.

Authors

Lorenzo Martini¹, Lorenzo Picco², Andrés Iroumé³, Marco Cavalli⁴

Affiliations

¹ University of Padova, Department of Land, Environment, Agriculture and Forestry, Padova, Italy. Electronic address: lorenzo.martini.2@phd.unipd.it.
² University of Padova, Department of Land, Environment, Agriculture and Forestry, Padova, Italy; Universidad Austral de Chile, Faculty of Engineering, Valdivia, Chile; Universidad Austral de Chile, RINA - Natural and Anthropogenic Risks Research Center, Valdivia, Chile.
³ Universidad Austral de Chile, Faculty of Forest Sciences and Natural Resources, Valdivia, Chile.
⁴ National Research Council, Research Institute for Geo-Hydrological Protection, Padova, Italy.

PMID: 31539952
DOI: 10.1016/j.scitotenv.2019.07.303

Abstract

River systems are continuously affected by multiple natural and anthropogenic phenomena. Among major natural disturbances, volcanic eruptions have the capability to overthrow the forms and to modify dramatically the morphological setting and sediment connectivity of the system. Moreover, the input of sediments in the channel network can lead to active channel widening, bed aggradation and river scouring, which in turn may affect downstream human settlements. In this context, the present research aims to investigate sediment connectivity by means of a geomorphometric index in a catchment affected by an explosive volcanic eruption in order to assess its variation before and after the disturbance. We developed a workflow exploiting the use of open source data (i.e., Global Digital Elevation Models, satellite imagery) to represent the impedance to the sediment fluxes and to apply the Index of Connectivity (IC) in this context characterized by the lack of high-resolution topographic data. The study area is the Blanco River basin, southern Chile, which was heavily affected by the eruption of Chaitén volcano (2008-2009) that caused the partial destruction of the forest and the profound alteration of Blanco River's morphology. The application of the IC on different land cover scenarios, derived by combining field observations and satellite image classification techniques, showed an increase in sediment connectivity after the volcanic eruption. In addition, the results highlighted different patterns of connectivity according to the expansion of the active channel induced by the massive input of pyroclastic material. The approach proposed in this study case offers a methodology to investigate sediment connectivity in a river catchment affected by natural disturbance where high-resolution data are not available. The results of the study help to improve knowledge on the effect of volcanic eruptions in the hydrologic catchment and to improve watershed management strategies in such kind of environment.

Keywords: Chile; Land cover change; Natural disturbance; Open source data; Sediment connectivity.