Monitoring soil erosion features using a time series of airborne remote sensing data: a case study Wild Coast, South Africa

Abstract

Soil erosion is a major geohazard that may pose both localized and off-site threats. Erosion by wind and water has caused severe land degradation in the Eastern Cape and if left uncontrolled may have detrimental consequences in critical environments along the Wild Coast. Development of a monitoring protocol to predict the susceptibility of the Wild Coast to erosion is necessary for the mitigation and prevention of further degradation. The development of such a monitoring protocol is based on the premise that erosion in the future is likely to occur under the same conditions that led to historical erosion processes. This paper focuses on the evolution of some large wind and water erosion features within the Xolobeni coastal strip along the northern Wild Coast that have been mapped from historical, multi-temporal airborne remote sensing data using initial results of sequential Maximum Likelihood classifications. Although image analysis suggests erosion is initiated by anthropogenic factors, the wind regime in the region is responsible for the preferential growth of elongated features that trend in same direction as of the dominant winds. Erosion is generally occurring at an accelerated rate. Peripheral vegetation was found to act as a wind barrier, effectively preventing the spread of parabolic dune erosion features. Minimisation of bare soil patches in croplands and along access tracks will curtail the creation of new wind blowouts and gully erosion features. The spread of these features can be prevented by establishing indigenous vegetation barriers on the intact soil along the fringes of the degraded area before establishing cover of plant species capable of stabilising loose sand. Such mitigation measures can be used to ensure that further degradation along the pristine Wild Coast is minimised.