Building Drought-Resistant Soil Map by Using GIS

Abstract

In order to manage the drought caused by changing climatic conditions, the reactions of the soils against the water scarcity must be known. In this research, drought-sensitive soil map was made in Izmir province by using soil properties which are effective in the resistance of soils to drought. These properties were examined in a GIS based model under 4 different headings as soil taxon, geomorphologic units, topography and physicochemical parameters of soils. The water holding capacity of soil taxon varies according to their genetic structure and horizon characteristics. The soil taxon was grouped according to their horizon depth, genetic origin of the parent materials, water holding capacity and they were graded in terms of resistance to drought. The topographic structure of the land was taken into consideration especially in terms of the degree and the shape of the slope such as concave-convex-linear straight etc. Geomorphological units are considered as another important parameter. Soil water budgets can also differ in terms of formation characteristics and location of each geomorphological unit. For example, lands have poor drainage condition, marshes, land around the lagoonary system, old lacustrine flat lands have a location close to surface and subsurface water. In addition, independent of the above mentioned parameters, the physical and chemical properties of soils such as texture, organic material and lime content effect soil water holding capacity. In this study, in order to determine the coexistence of the parameters effecting the soil water budget, a query model which is compatible with Analytic Hierarchy Process method has been formed in GIS. For this purpose, 22 soil great group and 9 soil parameters for each soil great groups were used as sub variable parameters. As a result of the research, a 4-graded drought-resist soil map was created as a base map for drought management projects.