Evaluation of the Effects of Earth Surface Terrain on Land Suitability of Various Landuses (Case Study: Urmia County)

Introduction
In the contemporary era, vital environmental resources such as water and soil have experienced degradation. This is mainly resulted from increasing population, development of environmental harmful activities, inappropriate management and so on. Today, development beyond ecological thresholds and degradation of the main factors of development and human survival has turned into one of the major challenges of human society. If this trend continues, the world society will face with various problems such as food security, environmental conservation and preservation of natural heritage. From the perspective of land use planning, development of economic activities without taking into account the potentials and the degree of production capacity of land resources can lead to various environmental, social and economic problems in a specific region. Therefore, it is essential to understand appropriate management of land resources and its parameters for land sustainability.
Given the physical conditions of land such as topography and landforms in Urmia region, as the limitations for development, it seems that analysis of land characteristics and identifying limitations and potentials of this region can be used as an effective tool for development activities. The present study is aimed at answering this critical question that: how much topographic and landform conditions can affect land suitability for development in Urmia County. The results of this study helps to make a background for further evaluation of the land for determining various land uses in the region.  
Methodology
Multi-Criteria Evaluation (MCE) method was used to identify suitable classes for developing activities. MCE is a method for combining data according to their preferences in making a given decision. At a conceptual level, MCE involves qualitative or quantitative weighting, ranking of criteria to reflect their importance to either a single or a multiple set of objectives (Heywood and et al., 2006). Since the last decade a number of multi-attribute (or multi-criteria) evaluation methods have been implemented in the GIS environment by WLC and consistency analysis in Analytic Hierarchy Process (AHP). Among these procedures, the WLC and Boolean overlay operations are considered as the most straightforward and the most often employed. WLC  is based on the concept of a weighted average. The decision maker directly assigns the weights of ‘relative importance’ to each attribute map layer. A total score is then obtained for each alternative by multiplying the importance assigned for each attribute by the scaled value given to the alternative on that attribute, and summing the products over all attributes. When the overall scores are calculated for all of the alternatives, the alternative with the highest overall score are chosen.
Results and discussion
Operations of overlaying layers are including:
1. Map A
In order to produce map A, at first stage, slope and elevation parameters were compared. The Statistics of this map show that the highly suitable and suitable classes cover 31.66% and 30.31% of the total area, respectively. The results also show that the combination of the slope and elevation layers has covered approximately 40% of the total areas in limited and not suitable classes. 
2. Map B
In order to produce map B, the standardized layer is overlaid with map A. The results of the topographic map indicate that only 21 percent of the total area is highly suitable for developing activities. In the second class, the suitable, covering 22 percent of the total area, the lands are suitable for some special activities. 
3. Map C
By overlaying land type and map B to produce map C, more filtering was applied in structural land layers for developing activities. This phase can be regarded as the milestone of the layers overlaying process. In other words, in this step, by adding land type layer, main characteristics of land are combined with the geomorphology map of the region. By producing geomorphology map, the highly suitable area was decreased, significantly. Therefore, the highly suitable area is decreased to 13.02 percent, which indicate the high effeteness of the land type in filtering of natural parameters for developing activities. 
In final map, the drainage layer as an effective parameter was used in the analysis. The drainage map is generated from river density and line density function. The results of this map show that approximately 11 and 21 percent of the total area is attributed to two classes of highly suitable and suitable, respectively. By adding drainage layer to geomorphology map, the areas of the two mentioned classes were significantly decreased. According to final land suitability map, 33 percent of the total area is related to the classes of highly suitable and suitable, 28 percent to the class of marginally suitable and 38 percent to the class of not suitable.
Conclusion
The results of overlaying the parameters represented that topographic elements have played significant role in filtering of land suitability for developing activities. The results of overlaying the land evaluation maps with proposed land suitability have demonstrated that the classes of marginally, very low and not suitable, with slope of 20.18, 28.69 and 42 percent, respectively, have severe natural limitations. The possibility of developing activities is not practical in approximately 67 percent of the total area. Therefore, topographic and landform characteristics of the region are the main constraints in development of the activities in Urmia County. Based on these results, development in Urmia involves prioritization of environmental issues and sustainable management of natural resources.