The speed of urbanism development causes remarkable changes in the manner of land use. Revelation of these changes and preparation of appropriate maps on the land use and land cover become important. The use of land survey traditional methods is no longer appropriate due to time consumption and high costs and the application of new and effective methods is necessary in this regard.
Capability of measurement and analysis of the status, of the land use/ land cover changes with the aid of numerical data for remote-measurement and geographical information system may play a conspicuous role in the management and control of such changes.
City of Gorgan, center of Golestan Province, is considered one of the economic, social and cultural centers of the province and area. As per the investigations inserted in the national somatic plan report, during the past decades the country's urban network system, like other urban places of the country, has attracted population and has been exposed to anomalous development of the urban space.
Study of the relation between forestry and agricultural lands change as per the size and distance from constructed lands: Occurrence of the agricultural high grade lands and beautiful forestry landscapes in the vicinity of the area of study and non-principled changes in vegetative cover and land use in forestry, urban and agricultural areas during the recent years especially acquisition of the centrality of the province since 1997 deem the study of the relation of the land use/ land covers changes in the area and evaluation of the urban development effects on the mentioned lands necessary.
Fuzzy analysis: For the purpose find out quantity change land use types, ground cover especially built lands we utilized post classification comparison. In order to at first provide image from IRS-1D LISS III in 2007, so that TM image in 1991 from the case study designated although land use map and aerial photo for evaluation accuracy.
Image's of 2007 had been Geo-referenced with utilize 26 points, then from the image to image 1991 and with basis 2007 image. Atmospheric rectify accomplished with ATCOR3 method, and the RMSE record 0.3. As if about these rules are not correct the value of correctness or incorrectness between 0-1.
Results and Discussion
The results show that the frequency of the occurrence of all possible combinations resulted from the two maps in the form of two-dimensional table causing the two maps of the classification of the images belonging to 1991 and 2007 to be overlapped. The intersection table of the categorized images indicate that during this ten year period, of the total forest land of 2064.02 hectares, and 216.54 hectares have changed into agricultural land and 49.82 hectares to urban land use. So of the total agricultural land of 6414.31 hectares 725.34 hectares have been changed into urban between 1991 and 2007.
The comparison images in six classes indicates that for class 1 agriculture land the smallest pixel size was 112.64 and change value 54.35 percent. In sixth classes, for the largest pixel size that is the change value was 7.21 percent. Also forestry land, the smallest pixel size was 62.19 and change value 93.22 percent so largest pixel size in 2842.17 was equivalent to 9.34 percent change, Where most of the changes that have occurred in the southern of Gorgan city.
The results show of the examination of relation between agricultural land change and distance from city for different classes that in the average distance of 424.36 m from the urban, transformation rate agriculture land was 1947 pixel and forestry land 4508 pixel for class 1. So, such rate was 1567, 2761 pixels for class 2, this showing a decreasing trend. The correlation rate between distance evaluation and agricultural and forestry lands change rate with the explanation coefficient of 0.93 and 0.82 shows the meaningful relation between these two variables.
Analysis of land use with neighborhood functions, and distance from the city show us that demolition rate and transformation increase in basis proximity to settlement and built lands, and with far away from settlements and built lands it has decreased. Results show that agricultural and forestry land use change is in basis fragment size. In the first stage southern parts especially around Naharkhoran forest park and next stage south western, north eastern and the west of Gorgan more affected in danger of urban lands change.
Regarding the occurrence of desirable agricultural lands, beautiful forestry landscapes and resources, the agricultural and forestry changes trend in the vicinity of the province center are not consistent with urban constant development indices. Transfer shares between urban, agricultural and forestry land uses for 1991, 2007 and 2020 were calculated to be [18.7, 39, 42.3], [33.7, 34.9, 36.2] and [37.3, 29.4, 28.8] respectively showing the increase in the urban level and decrease in the agricultural and forestry lands.
The use of the change clarifying methods with the aid of satellite images and the analytic functions of distance and land use plot sizes in GIS environment are very desirable for examination and determination of the trends and models of the important and meaningful changes of land use/ land covers such as deforestation and the change of agricultural lands into man-made places.
This study is considered a starting point for the conduction of broad studies in this field. Combination of other factors and variables effective on land use/ land cover changes, such as economic and social variables and other spatial characteristics can develop more precise and efficient models. Anyway information used in this study of high importance in the Gorgan city development management and supervision and plays basic role in strategies adoption and substantial policies determination of land preparation and fundamental use of land capabilities. It is therefore commented that:
- Since the city of Gorgan as center of province, has conspicuous social, tourist, economic and industrial attractions in the area. It is recommended to conduct supervisory actions on urban and habitation development projects as per a precise and coherent schedule.
- In order to present optimum model for urban somatic development and minimize the inappropriate environmental effects resulted from human interference, it is necessary to consider social, economic and environmental parameters in future studies.