Land Use/Land Cover Changes Detection in Cities and the Resulting Environmental Risks (Case Study: District 18 of Tehran Metropolis)

Overloading in Tehran's 18th district has caused widespread unsustainability in the district. This study has revealed changes in land use/land cover and identified possible environmental risks in the district. The research method is based on a descriptive-analytical and causal method. The research process was as follows: first, satellite images for 2002, 2013, and 2024 were prepared from the USGS website, and then an RGB image was prepared and digitized using ENVI software. In the next step, the trend of land use/ land cover changes during the three mentioned periods was examined. Three classes of land use (green cover, built-up land, and barren land) were determined, and the desired layers of land use/ land cover types were processed and extracted. Finally, with the help of the Delphi technique, possible environmental risks resulting from changes in land use/ land cover in the study area were identified. The results indicated the area of built-up land in 2002 was 22.4 hectares, which increased to 27.3 hectares in 2024. Meanwhile, the area of green cover, which was 5.4 hectares in 2002, decreased to 13 hectares in 2024. The area of barren land, which was 9.5 hectares in 2002, decreased to 5 hectares in 2024. The results also illustrate land use/ land cover changes in the study area can bring about numerous environmental risks.
Extended Abstract
1-Introduction        
Due to the existence of barren spaces in it, district 18  is currently being developed with massive growth in residential-industrial construction. This research is important and necessary considering the characteristics of District 18 of Tehran Metropolitan City, which is located in the future growth and development area of Tehran on the one hand and has become the location of various production and industrial units and a center for settling immigrants and poor people of Tehran due to its barren and empty lands. Therefore, the purpose of this research is to reveal the changes in land use/cover in 2002, 2013, and 2024, and to identify the possible environmental risks resulting from these changes. In this regard, the research questions are: (1) What is the status of land use/cover changes in District 18 of Tehran Metropolitan City during the mentioned periods? (2) What are the most important environmental risks resulting from land use/cover changes in the study area?
 
2-Materials and Methods
The study area is the territory of Region 18, which is located in the southwest of Tehran. The present study is of an applied nature, and in terms of its purpose, it was conducted using a descriptive-analytical and causal method. Data collection was based on documentary and survey methods: (A) Documentary method: Includes the examination of Landsat ETM+ satellite images from 2002, L1TP from 2013, and L1TP from 2024 to determine the extent of land use changes in the study area. (B) Survey method: Includes ground control of images using GPS and observation tools. Data analysis was also carried out using the following process and methods: (A) Quantitative method and remote sensing (RS) and GIS processing, including: (1) Identifying more than 37 ground control points (GCP) with the help of UTM reference and recording their position by GPS receiver to correct the geometric images, (2) Further clarifying ETM+ and L1TP images by performing data fusion operations to increase the spatial resolution of the images, (3) Image fusion through the Brovy method, (4) Supervised classification of images using the maximum similarity algorithm, (5) Performing accuracy assessment, and (6) Detecting land use/cover changes using the Normalized Difference Vegetation Index (NDVI). (B) Qualitative method: In this method, the Delphi technique was used with interviews with 17 experts, and questions were raised about the risks arising from land use/cover changes in the region.
3- Results and Discussion
The results of the surveys show that, based on the calculations, green cover has decreased from 14.49 percent in 2002 (5.41 hectares), to 13.30 percent in 2013 (4.96 hectares), and 13.05 percent in 2024 (13 hectares), respectively. The results also showed that the area of ​​built-up land has increased from 59.98 percent in 2002 (22.4 hectares), to 70.40 percent in 2013 (26.3 hectares), and 72.99 percent in 2024 (27.3 hectares). The results also show that the area of ​​wasteland in 2002 was 25.53 percent (9.53 hectares) of the region's area, but it decreased to 16.89 percent (6.1 hectares) in 2013, and to 13.95 percent (5.2 hectares) in 2024. The results of the study also indicated the risks of the human environment, with an average score of 3.89, will be higher than the risks of the natural environment (3.65). Also, the destruction of ecosystems due to the development of construction (with an average score of 4.56), soil loosening and increased land subsidence (with an average score of 4.53), reduction of ecosystem services (with an average score of 4.53), reduction of food security due to the expansion of residential, commercial and industrial construction (with an average score of 4.42), and increase in sudden environmental crises (such as storms, earthquakes, floods, etc.) (with an average score of 4.40) will be the highest risks in this regard. In total, the overall average risk at the level of the study area will be high, with an average score of 3.74.
4- Conclusion
The most important reasons for land use/cover changes in the region include: the existence of vacant and empty spaces, and the availability of a platform for construction growth; extensive densification by the region's municipality; the emphasis of the Tehran City Master Plan on the future growth of Tehran in this area; the existence of industrial and workshop units, and the attraction of labor to operate in the region; the location within various communication arteries between the metropolises of Tehran and Karaj; the weakness and inadequacy of some laws and regulations; the lack of effective monitoring mechanisms; and the lack of integrated urban management. To control land use/cover changes in the study area, it is increasingly necessary to first amend conflicting laws and regulations and develop monitoring mechanisms. Given the excessive expansion of unauthorized construction in the region, it is necessary to review the implementation of some legal provisions, as well as tighten the loading at the regional level, by increasing the number of construction police forces, developing smart cameras to control construction, and restricting the issuance of construction permits (industrial, residential, and service). In addition, prohibiting the issuance of new construction permits for density sales and identifying new financial sources for the regional municipality can prevent the escalation of problems and excessive destruction of the region's ecosystem and reduce the possibility of increasing environmental risks. Another effective solution to control land use/cover changes and environmental risks is to develop green cover in empty and barren spaces in the region to, on the one hand, prevent the growth of excessive construction and, on the other hand, help restore the damaged ecosystem of the region. Finally, developing integrated urban management is essential to prevent organizational inconsistencies and create a unified approach to construction, to prevent environmental destruction and instability.