POTENTIAL EROSION DUE TO PRODUCTIVE RECONVERSION IN LLAY – LLAY BASIN (CUENCA), CHILE. APPLYING RESPONSE UNITS TO EROSION

Abstract

The objective of this study was to determine potential erosion due to agricultural productive reconversion in Llay-Llay basin (sub-basin) located in the Aconcagua valley, at the V Valparaiso Region in Chile, through the adaptation of  Marker´s et al. (2001) erosion response units (ERU’s), which underwent a hierarchical analytic process previous to final spatial modelling. ERU´s validation was carried out on the basis of transport capacity and slopes stability morphometric indexes. ERU´s outstand due to their qualitative nature and to their homogeneous geo-spatial distribution within the study area, related to erosivity and erodability factors. In order to understand productive reconversion evolutionary process in Llay–Llay sub-basin for the last thirty years, the normalized vegetation index (NDVI) was applied through the analysis of Landsat multispectral satellite images ETM, while for modelling such topographic variables as soil slope and slope exposure, as well as for calculating morphometric indexes a terrain digital elevation model (MDE), with an appropriate spatial resolution was used. ERU´s category of very high susceptibility to erosion for Llay- Llay sub-basin corresponds to an area covered by paltos (avocado) plantations in slopes, where slopes stability morphometric index showed high values, while the areas having the least danger of erosion, according to ERU´s, low susceptibility class resulted to be those covered with dense arborecente scrub.