Risk Assessment of Vegetation Degradation Using GIS

Abstract

The entire land in the Southern Iran faces problems arising out of various types of land degradation, of which the vegetation type forms one of the major ones. The Payab basin (522,470 ha), which covers the lower reaches of Mon d River, was chosen for a test risk assessment of this type. The different kinds of dat a for indicators of vegetation degradation were taken from the records and publish ed reports of Iran governmental offices. A new model was developed for assessing th e risk of vegetation degradation. Taking into consideration nine indicators of vegeta tion degradation, the model identifies areas with ‘Potential Risk’ (risky zones) and areas of ‘Actual Risk’ projecting the probability of the worse degradation in future. The preparation of risk maps, based on the GIS analysis of these indicators will be helpfu l for prioritizing the areas to initiate remedial measures. A hazard map for each indicator was first prepared in GIS by fixing the thresholds of severity classes of the indicator s. The risk classes were defined on the basis of risk scores arrived at by assigning the ap propriate attributes to the indicators and the risk map prepared by overlaying some nine hazar d maps in the GIS. Areas under actual risk were found to be widespread (93%) in th e basin and when the risk map classified into subclasses of potential risk with d ifferent probability levels the model would project a statistical picture of the risk of vegetation degradation.