فصلنامه پژوهش های جغرافیای طبیعی
پیاپی 125 (پاییز 1402)

The expansion and development of cities and the increase of urbanization are some of the current characteristics of human societies, especially in developing countries. Density and population growth in cities have led to the expansion and development of urban areas and changes in urban land use. In this research, a remote sensing technique was used to identify the patterns and examine the spatial changes in the surface temperature in different areas of Isfahan City. Using thermal equations and a similarity centre algorithm, the temperature of the earth's surface has been calculated for the periods of 1365 to 1401. The supervised classification of the most similar method was used to evaluate the changes in the land use of the studied area, which includes built uses, gardens, vegetation, and lands without vegetation. The results of the comparison of land use between 1365 and 1401 within the scope of studies show that during the mentioned period residential use increased by 175.94 square kilometers and garden use by 74.28 km shows a decreasing trend. Also, we see a decrease of 39.03 km in the use of vegetation and a decrease of 217.75 km in the use of areas without vegetation. The results of the earth surface temperature survey show the expansion of the earth surface temperature during the study period in Isfahan city. Based on this, in the studied period, the earth's surface temperature increased in the east and southeast regions. Examining the isothermal lines shows that the temperature of the earth's surface around the city increased significantly in terms of temperature and extent.

Landslides are a critical geohazard, often triggered by seismic activity, intense rainfall, and water table fluctuations. Understanding the complex interplay of these factors is a key task in hazard assessment and mitigation strategies. This comprehensive study investigates the regional potential for water flow dynamics, displacement mechanisms, and landslide genesis. Based on a dual approach of rigorous fieldwork and meticulous laboratory analysis, approximately 5 kg of fine-grained clay and 100 kg of coarse-grained material were collected for in-depth mechanical property testing. These investigations focused primarily on assessing Atterberg limits and shear strength characteristics. The results showed a striking correlation between the water table and the site's structural integrity. In particular, the marl and alluvial layers exhibited a significant decrease in resistance, ranging from 40% to 55% and 60% to 80%, respectively, in different regions of the study area. In addition, the cohesion of the layers decreased with increasing slope steepness, resulting in a reduction in internal friction angles. This empirical evidence highlights the region's susceptibility to increased landslide risk, particularly in precipitation-induced surface water infiltration and potential seismic upheaval, such as the powerful 7.3 magnitude earthquake in Sarpol Zahab in 2017. These combined factors highlight the imminent threat of landslides and call for proactive risk management and disaster preparedness measures.

The present study aims to investigate the temporal-spatial trend of horizontal visibility in the southern coasts of the Caspian Sea. For this purpose, horizontal visibility and climatic parameters (relative humidity, temperature, precipitation, and wind speed) were obtained in 13 selected meteorological stations from 1951-2010. After the data screening, the temporal changes of the perspective were examined. Also, Ridit tests were applied to examine the trend of horizontal visibility, and a correlation coefficient was used to identify the relationship between the climatic parameters effective in reducing horizontal visibility. The results of the research showed that the average annual dispersion of horizontal visibility in the studied stations experienced relatively different periods; the first period from 1951 to 1976 period of horizontal increase, the second period from 1977 to 1985 period of noticeable decline, the third period from 1986 to 2002 fixed period (no fundamental change) and the fourth period from 2003 to 2020 relative increase. Among the stations, the highest negative correlation coefficient was experienced by Astara station, with a value of -0.47, and the lowest was experienced by Sari station, with a value of -0.07. In the correlation between horizontal visibility and precipitation in the studied stations, the maximum significant negative correlation was observed in the Manjil station (with a value of -0.15) and the least in the Maratape station (with a value of -0.012). The correlation between horizontal visibility and temperature is direct and positive in most stations, and the maximum positive correlation is assigned to the Astara station with a value of 0.38. It also showed a negative correlation between wind speed and horizontal visibility. The inverse correlation's maximum and minimum range fluctuates between -0.28 in Sari and -0.08 in Babolsar.

Alluvial fans are ideal places for investigating the effects of geomorphological processes and landforms on soil properties. This study aimed to investigate the effects of geomorphological forms and processes on physical and chemical properties of soil in an alluvial fan located in the southeast of Shah Ghaib salt diaper. The study area alluvial fan is composed of three surfaces including very old, old and young. The phosphorous, potassium, absorbable sodium, calcium carbonate, saturation moisture of soil, water’s holding capacity in soil, soil texture, and organic carbon parameters were measured in 72 soil samples on the alluvial fan surfaces.The results showed that the sodium, potassium, EC, calcium carbonate, phosphorous, and holding capacity of water, silt, and clay parameters were higher in the interfluves than the channels in inactive (very old and old) surfaces. The organic carbon, pH, saturation moisture of soil and percentage of sand is higher in the channels. Also, the sodium, potassium, EC were more in the young compared to the old and very old surfaces. The PH, phosphorous, and saturation moisture of soil were higher in the old surface than in the young and very old ones. The amount of calcium carbonate, water’s holding capacity in soil and percentage of silt were highest in the very old fan surface. The correlation coefficient between the measured parameters of the soil indicated that there are strong positive relationships between the clay and the sodium, electrical conductivity, calcium carbonate, and potassium. In general, the results show that geomorphological processes such as entrenchment in channels and weathering on the surface of the interfluves have controlled on the values of the physicochemical parameters of the soil in the study area alluvial fan.

Evaluating the flood potential of different watersheds is one of the important measures in the field of reducing damages caused by floods. As one of the flood-prone basins of Gilan province, the River catchment has always caused a lot of damage to the residents of the region in recent years. Therefore, due to the lack of studies in this basin, the current research has attempted to zonate the risk of flooding, and for this purpose, the AWBM model and the Fuzzy-ANP method have been used. , 2014, 2017 and the end of 2018 are estimated to increase and equal to the floods of 1990, 1993, 199, and 1997. In the spatial zoning of flood risk, 10 effective factors incluincludingecipitation, temperature, distance from the river, slope, slope direction, height, land use, vegetation, geolo   and soil were used. In the analysis of the results, it is estimated that the highest risk of flooding is in the southern areas and the outlet of the basin to the Caspian Sea, and the settlement in the river, lack of attention to watershed management, destruction of forests and pastures, and land use change are among the most important factors affecting this issue. In total, 90.3% of the area of the basin has the highest risk of flooding from a geographical point of view.

Rivers in their path are always struggling with a phenomenon called erosion, which on the one hand causes many changes in the geometric shape of the river section, morphology and hydraulic characteristics of its flow, and on the other hand, it brings irreparable effects to the lands adjacent to the channel. One of the main sources of sediment production is the erosion of river banks. In this regard, investigating the amount of coastal erosion is one of the management strategies. The area under study is the banks of the Jajroud River, between Letian Dam and Mamlo Dam, with a total of seven sections. In this study, for the erosion of the river bank and estimation of the amount of sediment from the method or model of estimation of the bank and foot of the bank (BSTEM) in this model, the geometrical parameters of the channel (angle of the wall and height of the bank and the distance of the toe of the bank and its angle), the height of the layers And their species, flow information and vegetation cover and other side cover materials have been extracted and used. In this research, the depth of the flow in a spiral discharge mode and the flow duration of 12 hours were used to model the bank erosion. The model models the amount of bank destruction by calculating the shear stress and soil resistance. The results of the research showed that all sections except section 6 have high erosion. The difference in erosion values in different stages was mostly due to the type of bank sediments and bank slope angle. In terms of bank stability and safety factor (FS), the most unstable bank was in section 5 and the most stable bank was in section 6 of the river.

Recognition and evaluation of wetland ecosystem services and ecological coherence can be effective in the supply and sustainability of services at different levels. In this regard, the current research has evaluated the ecosystem services of Zarivar wetland by using the rapid assessment ecosystem services approach and the millennium ecosystem services assessment framework for the sustainability and development of its services. In order to evaluate the services in four categories of provisioning, regulating, cultural, and support services, the rapid evaluation approach of Ramsar Convention services was used. Data collection was based on interview tools and questionnaires from local experts, experts from wetland-related institutions, and members of environmental associations in the region, 55 of whom were purposefully selected. The Ecosystem Service Index (ESI) was used to compare and score the importance of services. The results showed the positive potential of Zarivar wetland in all 4 categories of services, such that cultural services have the highest positive potential (ESI=0.66) and supporting services (ESI=0.57), regulating services (ESI=0.42) and provisioning services (ESI=0.38) were in the next place. The comparison of services provided at different levels showed that most services were reported locally. The correlation test showed a positive and significant relationship between different wetland ecosystem services, which causes synergy between its services. The results of applying the rapid assessment approach can be used in local and national policy frameworks and decision-making processes.