Erosión y desertificación.-Identification of active erosion areas and areas at risk by remote sensing: an example in the Ésera—Isábena watershed, Central Spanish Pyrenees

Abstract

ABSTRACT The identification of eroded areas at basin scale can be very useful for environmental planning and can help to reduce land degradation and sediment yield. In this paper remote sensing techniques are used to discriminate eroded areas and areas at risk in a badlands landscape developed on Eocene marls, in the Ésera—Isábena watershed (Spanish Pyrenees). The spatial distribution, the scarce vegetal cover and the high level of erosion let a good visual and digital discrimination of badlands, as opposed to other land covers and surfaces. A maximum likelihood supervised method was used to discriminate heavily eroded areas (badlands) from scarce or densely vegetated lands. The classification distance was used to obtain thresholds for eroded areas and areas at risk. Two error statistics (sensitivity and specificity) where used to determine the most adequate threshold values. The resulting map shows that most areas at risk are located surrounding the badland areas.