International Symposium on
Drylands Ecology and Human Security
Risk Assessment of Soil Degradation Using GIS in Parts of Mond Basin, Southern Iran
Masoud Masoudi 1& Elham Asrari 2
1 Department of Desert Region Management, Agricultural College, Shiraz University, Iran
2 Headquarters of Environment in Fars Province, Shiraz, Iran
The present paper attempts to evolve a new model by considering various indicators of different types of soil degradation, namely, water erosion, wind erosion and soil salinity for finding areas with higher rate of degradation which are called Potential Risk Areas (risky zones) in this paper and measure probability of occurrence of worse step of degradation in these areas. The identification of areas that are more vulnerable to degradation from those with less risk of degradation in future can be helpful for improving our knowledge about the extent of the areas affected and, ultimately, for developing measures to keep the problem under control. The entire land of Southern Iran, south of the Zagros belt, faces problems arising out of land degradation of which soil degradation types are major forms of land degradation or desertification in these areas. The Mond river basin, located centrally to this zone, has been selected as a test area to assess the risk and kind of soil degradation. For this purpose two sub basins of the Payab and Qareh Aghaj have been chosen for detailed study as these two provide enough variation in climatic conditions like rainfall and topography. The different kinds of data gathered from the records and published reports of the different governmental offices of Iran have been used for this purpose. The thresholds for the severity classes of indicators have been established and then the hazard map for each indicator of types of soil degradation has been prepared in a GIS. The risk maps of water erosion, soil salinization, and current state of wind erosion have been produced for each of the two sub basins. The risk classes of different risk maps are calculated on the basis of classification of risk scores derived by cumulative effect of all the attributes of indicators after overlying them in the GIS. It was possible to distinguish the areas under ‘actual risk’ from areas under ‘potential risk’ of soil degradation types. Also areas under potential risk are classified to subclasses with different probability level to show a statistical picture of risk in future. The final map of risk of soil degradation is produced by overlaying all three maps of degradation types. Between the two basins the overall environmental condition in the Payab sub basin is worse. Results show that potential risk areas are much widespread than areas under actual risk in the upper reaches (Qareh Aghaj sub basin) of Mond basin, indicating further threat of desertification in future. While per cent areas under actual risk are much extensive in the lower reaches (lower reaches), indicating the higher degradation at present. The GIS analysis has also helped to fix priority areas for remedial measures to lower the effects of types of degradation.
Keywords: soil degradation, GIS, Indicator, Actual Risk, Potential Risk