Extended Abstract
Introduction
Certain kinds of land use can change the hydrology of the Watershed, altering the way water and pollutants move through the drainage basin. For example, as an area of land is converted from open space (e.g. woodland) to residential, the amount of runoff for that area of land will increase as the amount of impervious surface increases. Rain, which would have once seeped into the soils beneath the forest floor and been absorbed by tree roots, instead flows off impervious surfaces (roofs, driveways, streets, parking lots, etc.) into the nearest stream, pond, or lowland area. Landuse change due to human activities, is one of the important issues in the regional planning. In many areas of Iran, land use and land management, regardless of land abilitycaused the loss of capital and reduced the capacity of the environment. Land suitability is the fitness of a given type of land for a defined use. The land may be considered in its present condition or after improvements. The process of land suitability classification is the appraisal and grouping of specific areas of land in terms of their suitability for defined uses. Land evaluation is a process for matching the characteristics of land resourcesfor certain uses using a scientifically standardized technique. The results can beused as a guide by land users and planners to identify alternative land uses.
 
Materials & Methods
In this study, using multi-criteria decision- making methods and GIS, modeling suitability of land for urban development, and determining the compatibility between existing applications, in Ziarat watershed of Golestan province, was investigated.Ziarat watershed is important in Golestan Province and yet critical in terms of land use change, erosion and flooding. In this basin, regardless of ecological capability for urban development and the lack of attention, land use change happened in the recent years. In this study, referring to the 10 experts in the relevant fields and using Analytical Hierarchy Process (AHP) is a weight for each criterion. The Analytic Hierarchy Process (AHP) is a structured technique for organizing and analyzing complex decisions based on mathematics and psychology.In this study, combining maps of criterion and suitability of land for urban development of SAW and TOPSIS technique was used. Finally, the study examines the compatibility between existing land use inZiaret watershed ofGolestan province.
 
Results & Discussion
 According to the results, the residential areas using TOPSIS and SAW techniques were 37 and 79.4 hectares of the total area of Ziarat watershed, respectively. But the current situation of the residential areas in the watershed were 141.3 ha. In modeling land suitability for urban development due to the presence of spatial dependency between criterion maps, the best way to combine criteria and calculate the suitability of the user, is using the TOPSIS technique. The results of land uses compatibility showed that, residential land use with compatibility 0.118245 was the lowest compatibility between current land uses in the watershed.
Conclusion
  Given the abilities of GIS and multi-criteria decision-making methods in modeling the suitability of land for urban development,the more accurate the expert opinions and the more updated the data and information, the better results will be achieved using these tools and techniques.Therefore this technique is very effective in the watershed in case of lack of data. Also, when there exist complications due to a number of qualitative and quantitative criteria, MCDM plays an important role.As the results of land suitability modeling using SAW and TOPSIS techniques with the aid of specific software functionality ArcGIS 10.1, it is clear that a small area of the basin have created conditions of urban areas. According to the results of land suitability modeling, the catchment area of residential areas is more than twice the land area.Also, residential areas have been constructed in the basin in inappropriate places such as steep slopes and river boundaries, and do not have residential conditions.