نشریه جغرافیا و مخاطرات محیطی
پیاپی 36 (زمستان 1399)

Floods are one of the biggest global problems, so with the increasing intensity and frequency of floods, global concerns about increased mortality and economic losses due to floods have increased. In this research, using geographic information system (GIS), satellite images, synoptic station data, hierarchical analysis (AHP), and layer integration (WLC) method, flooding potential of Qarah_su catchment modeling Has been. The final flood risk map was prepared based on a combination of climatic and physical factors and elements, i.e., ten factors of vegetation, altitude, flood channel, geology, land use, rainfall, distance from the river, slope, soil, and drainage density. The weight of each criterion was used by the Analytic Hierarchy Process (AHP), and the weighted linear composition (WLC) method was used for spatial modeling and layer integration to prepare the flood potential map. The results of flood risk zoning showed that the 4th class as a high-risk category with 21.7% and the 5th class with a very high flood potential with 8.4%, more in the northern mountainous areas. And are located in the center of the region. In total, about 31% of the catchment area is covered by high to very high-risk flood areas, and because they have the most considerable role in runoff production, they should be given special attention in terms of watershed management. Classes one to three with low to medium flooding potential are located in low-lying areas, slopes, and plains of the center, south, and west of the basin and cover more than 69% of the area.

Land is one of the inputs of the production sector. It plays an important role not only in the agricultural economy and natural resources but also in the economy of the whole country and it is necessary to pay attention to the land and the changes that have taken place in it. The present study was conducted to investigate the trend of land use change in Ojan Chay catchment using remote sensing and GIS. Multi-timer images of 1987 TM, ETM + 2002, and ETM + 2015 were used in this study, and land use maps were prepared based on digital processing of maximum probability and backup vector machine. The type of land use changes in the region was obtained. According to the results, the SVM method is more efficient for estimating land use changes in the study area so that the extracted results have a higher percentage of accuracy and kappa coefficient. From the results of evaluations, it can be deduced that the trend of land use change in some land uses such as agricultural lands and pastures is high. Agricultural lands have fluctuated from 33% to 37% over a period of 28 years and rangelands have decreased from 51% to 49%, with these two uses having the most changes. Finally, due to the fact that most of the changes in rangeland change have been related to agricultural lands and vice versa, therefore, the need to focus land management and improvement activities on this type of land use increases.

Floods are the most common natural hazards, the recurrence of which is increasing and the associated risks in urban and rural areas are of global importance, although their importance is not well understood for developing countries. The aim of this study was to zoning the flood risk of Dinevar River in Kermanshah province. Therefore, the HEC_RAS numerical model was used to simulate the flood and was used through the HEC-GEORAS. Using SMADA software, the peak flow rate was calculated and the flood zone with different return periods of 2 years, 10 years, 25, 50, 100 and 200 years is simulated area and with the help of digital depth model Water and land use layer, the amount of damage was calculated using the equation of depth function and damage in the return period of 25 years, 50 and 100 years. The results of this study show that the area of flood expansion zone in the return period of 25 years is 40.34 square kilometers, in the return period of 50 years is 43.51 and in the return period of 100 years, 44.28 square kilometers is endangered in terms of damage. 25 years is considered a baseline flood that shows significant damage, covering all farms, but floods affect parts of farms at lower returns. But it is controllable, while 25-, 50-, and 100-year-old floods have completely endangered many rural centers and farms. 50 years has been an average of 85% more, which requires flood control for sustainable management.

The process of soil erosion as the central focus of soil and water conservation studies in sustainable ecosystems is influenced by various natural and human disturbances. Besides, the overall structure and composition of an ecosystem are affected by changes in its landscape. Therefore, the present study was planned to investigate the relationship between landscape metrics and soil erosion patterns in the KoozehTopraghi Watershed located in Ardabil Province. In this regard, the 14 landscape metrics including Patch Density (PD), Largest Patch Index (LPI), Total Edge (TE), Edge Density (ED), Landscape Shape Index (LSI), Mean Patch Area (AREA-MN),  Mean Euclidean Nearest Neighbor Distance (END-MN), Landscape Division Index (DIVISION), Mean Patch Shape Index (SHAPE-MN), Splitting Index (SPLIT), Patch Cohesion Index (COHESION ), Effective Mesh Size (MESH), Aggregation Index (AI) and Percentage of Landscape (PLAND) were calculated using Fragstats 4.2.1 Software. Then, the severity of soil erosion in the study area was estimated using the Erosion Potential Method (EPM), which its performance has been confirmed by previous studies around the study area. Then, the results of landscape metrics and soil erosion calculation were interred to IBM SPSS Statistics software platform, and the established regression models were determined. The results indicate an inverse relationship between DIVISION, ED, and LPI landscape metrics with the specific soil erosion and a direct relationship between SHAPE-MN and AREA-MN with specific soil erosion of the KoozehTopraghi Watershed. The results of the present study confirm the different behavioral patterns of land features as a result of land degradation processes. These results can be used in effective and sound planning of land use management at watershed and landscape scales.

Nebkha is a sand dune formed in many arid and semi-arid regions by the accumulation of sediments around vegetation. The appearance and development of the sand dunes can be a sign of the expansion of desertification. The interaction between wind performance and the geomorphic characteristics of sand dune leads to heterogeneity in the distribution of sediment particles within sand dune. The aim of this study was to investigate the effects of hydrological and aeolian processes on the morphology of nebkha. Overall, 9 sand dunes were randomly selected. For each nebkha, sediment sampling was carried out from the different positions, including upwind and leeward slopes, dune top, edge, and the interdune spaces. Data on the parameters of particle size distribution, hydraulic conductivity and moisture were extracted. The measured particles were classified to 5 groups, including clay (> 2 µm), fine silt (2-5µm), medium silt (5-20µm), coarse silt (20-64 µm), and sand (65≤ 2000 µm). The accumulation of aggregates with different sizes along the interdune-dune continuum could exhibit the contribution of hydro-aeolian processes in sediment transport and deposition. The findings showed that average aggregate size reduced from the interdune areas to the dunes, and the finest aggregates were observed on the dune edge, illustrating the functioning of hydrological processes on the evolution of the nebkha structure. By contrast, predominant sediments within the nebkha structure mostly were coarse-grained (sand) fractions, illustrating the functioning of aeolian processes. Based on the findings, the processes involved in the evolution of dune include the saltation and creep of sand-sized sediments, transportation of sediments through runoff in the interdune space, as well as sediment-laden runoff that flows from the top of coppice dune into the edge positions.

In this study we have used the daily mean data from the Modern Era Retrospective Analysis for Research and Applications version 2 (MERRA2) assimilated data. From the MERRA2 data, zonal wind and temperature were obtained at 10hPa from 01 January 1979 to 04 June 2020.The temperature averaged around the polar cap for latitudes north of 60°N. This is a good measure of the overall temperature in the polar vortex.  Investigation of the polar temperature and zonal-mean zonal wind at 10hPa, is detected 19 and 13 major and minor SSWs events, respectively. According to the shows a rapid increase from 201.6K on 12 January to 253.4K on 23 January 2009 (∆T=51.8K). This is the largest increase in the polar temperature per 11-day in the entire MERRA-2 data set starting from January 1979 to June 2020. In this study life cycle of major SSWs is defined by dividing it into five periods. Onset (the first day of maximum zonal-mean zonal wind is reduced), growth (from onset day to zero day), maturation (from zero day to minimum zonal-mean zonal wind), decline (from minimum value to decay day) and decay (the first day of the easterly wind reversal to westerly) of typical SSWs. The result shows the shortest and longest growth periods, with 6 and 37 days, respectively, were recorded in the cases of January 6, 2013 and January 23, 1987. The longest maturation period, with 17 days of continuity, is dedicated to the warming of January 23, 1987. The longest decline period in this statistical period is 26 days, which is related to the warming of January 24, 2009. The shortest and longest life cycle in this statistical period are dedicated to cases on February 1, 2017 and January 23, 1987, respectively.

In current study, we underlined the trends of annual precipitation over Iran in relation with changes in high and low extremes and normal values of precipitation from spatial analysis point of view. To this end, the third version of Asfazzari national database with 10 10 km spatial resolution and daily temporal resolution for 46 years (1970/3/21 to 2016/3/19) is adopted. Trend analysis depicted that in the major parts of the country (approximately 80.9%) the annual precipitation has experienced decreasing trends which tend to reducing about 1.5 billions cubic meters of input water in the hydrologic system of the country. Our finding showed that the decreasing trends of precipitation prompted by large scale and global systems. However, the local factors (longitude, latitude, elevation, slop) are culprits for changing the effects of abovementioned factors. These factors cause the decreasing trends to be statistically significant solely in a part of 33.53% of Iran territory (northeast, parts of eastern of Iran, parts of inner slops of Zagros mountain chain, an area from Kerman to Isfahan, Charmahal-o-Bakhtiari, Kohgiloyeh-oBoyerAhmad, from west of Shiraz, and north of Bushehr to Sanandaj in the west of Iran). Furthermore, the results of our study illustrated that the decreasing trends are due to decreasing in high values of precipitation, particularly decreasing in the 75th percentiles and above of precipitation values. The areas which include increasing trends covered spatially spread areas of about 2.93% of the country. This area has not been able to compensate for the lack of precipitation due to decreasing trends in the area associated with statistically significant decrease in precipitation.

The environment is currently experiencing different changes that are caused by both nature-induced and anthropogenic processes. Land use changes in Gharesoo Watershed noted that there is a necessary need to study ecological quality in this region. In this paper, a remote sensing-based ecological index (RSEI) based on the pressure-state-response (PSR) framework, using the average data of summer images of Landsat satellite in 1989 and 2018 (ETM +/OLI/TIRS sensors), was used to evaluate the changes in ecological quality in Gharasoo watershed of Golestan province. Google Earth Engine (GEE) is used for acquiring and preparing indices, including an indicator of environmental pressure (NDBI), an indicator of environmental state (NDVI) and indicators of local climate changes in response to environmental changes and concerns (LST and LSM). After preparing the indices, the weight of each index was extracted using the principal component analysis (PCA), and then the ecological quality index was created based on the first component of PCA. Analysis of the first component changes using the thresholding method showed a decrease in ecological quality. So that the average RSEI index in 1989 was 0.57 and in 1397 this value reached 0.48, which indicates a decrease in RSEI. Also, the area of very good class in 1989 and 2018 is 32821.83 (16.267%) and 36879.66 (18.27%) hectares, respectively. Spatial variation analysis showed that the poor level of RSEI distributed mostly in the northern areas, and the ecological degradation was  attributed to the fast expansion of the built-up area, characterized by increasing greatly in the value of the normalized differential built up index (NDBI) in such areas.

Heavy rain resulting from atmospheric patterns, depending on the extent of activity and the time period of its occurrence, has adverse events and consequences such as floods. The present study was conducted in order to synoptic analysis of 171.5 mm heavy rainfall (March 19, 2017) leading to flood in Minoodasht city. The view of this study is a circular to environmental and first, the amount of rainfall at Minoodasht station was determined and by receiving upper atmosphere data from the website of the National Center for Environmental Prediction (NCEP / NCAR) and analyzing them, the causes of heavy rainfall was revealed. In order to study the synoptic conditions, using the Gardes software, sea level pressure maps were drawn, and in the upper atmosphere, geopotential height, wind vector, vorticity, omega, thickness, eddy and humidity (500 hPa level) were studied. The results of map analysis showed that during heavy rains, high pressure systems were formed in Mongolia and southern China and were caused a pressure gradient & strong front with prevailing low pressure system in Minoodasht. In the upper atmosphere, the presence of cut-off low-pressure blocking has been placed as a barrier to the west winds and has caused the flow of west winds to the study area. In addition, the high thickness of the atmosphere in the study area and the dominance of the amount of negative eddy, led to air instability and the presence of positive virtuosity cores and negative omega, indicates an unstable atmosphere on the days in the study area. Also, the inflow of moisture from moisture sources such as the Caspian Sea, the Aral Sea, the Black Sea and the Mediterranean Sea has provided special conditions for severe rainfall.

Resilience is an integrated approach to enhance existing capacities and reduce the vulnerability of human societies to a variety of environmental crises and hazards. In this regard, one of the most important crises and hazards that have overshadowed all over the world in recent years is the spread of the corona virus. Considering the negative effects and harms of coronavirus outbreak in different dimensions of human societies, the aim of the present study is the future study of Tabriz resilience against coronavirus pandemic. The research method in this study is a combination of quantitative-qualitative approaches with the nature of futures study, which in order to collect information is used from the Delphi technique of elites and city managers (30 experts in the field of crisis and risk management) and to analyze information is used from the technique of cross-impact analysis in software MICMAC. Findings indicate that the most influential among the studied drivers on other drivers in terms of urban resilience against the corona pandemic are related to economic drivers such as finding a new job if the current job is lost, the vulnerability of sources of income and the existence of institutions, finance supports the most vulnerable and most influential groups related to social impulses such as collective participation in dealing with the crisis and responding appropriately and behaving in critical situations. The results also show that due to the current situation and the lack of key and strategic drivers for effective system resilience, weak in economic and social structures, the city's management system and Iran's precarious position in the international arena, the future of Tabriz resilience based on environmental hazards (corona pandemic) will be unstable.

With the continuous development of urbanization, and the increase of uncertainty and risk, resilience has become an important criterion for urban safety. Urban systems, as dynamic and open space systems, present certain complex manifestations. Therefore, understanding urban resilience from the perspective of complex systems theory is important to achieve a full understanding of the composition and mechanism of operation of urban systems and then improve the scientific nature of urban system cognition and research. Urban areas have the largest population of the country and in addition to the nodes of consumption of resources and centers of innovation, theoretically and practically become the main area of ​​resilience testing against natural hazards, especially earthquakes. The aim of this study was to measure the resilience of Tabriz as the largest population center in northwestern Iran and at the same time one of the most seismic cities in the country against earthquake risk. This research is descriptive-analytical in terms of method and practical in terms of purpose. Based on this, Tabriz urban resilience has been evaluated based on 14 criteria in the form of 4 main components (social, economic, institutional, physical resilience) by Delphi method and by 50 experts. For data analysis, one-sample t-test, Friedman, Kendall and path analysis in the form of SPSS software were used. Findings showed that the resilience status of Tabriz city against the occurrence of a possible earthquake of social dimension, 2.19; in the economic dimension, 2.37; in the institutional dimension, 1.94; and in the physical dimension it is 2.57. In general, the resilience of Tabriz city against earthquakes, with an average of 2.33 is undesirable. Among the four components, the physical component with the sum of direct and indirect effects explains the alpha of 0.560 and is the most effective component in the resilience of Tabriz. The four dimensions of resilience, in total, could explain 0.345 of resilience in Tabriz.

In the decades, with the advent of technology and integrated management municipal solid waste, the methods such as recycling, biological treatment, heat treatment and sanitation have been used. The sanitary landfill method is considered as one of the strategies in the integrated waste management hierarchy and is more common and less costly than other disposal methods. The purpose of this research to identify the environmental problems and environmental risks the place of landfill residue of Tonekabon city is the RASCAL method. This approach is used to assess the risk of landfills that are not so large and it has been used to determine the risk of groundwater contamination and gas accumulation and factors that have a greater impact on the pollution of the two factors. According to RASCAL and AHP, the leachate collection system criterion, has the greatest impact on the risk of groundwater contamination. In the context of the risk of gas accumulation, the criterion of the type of waste and the type of gas produced has the highest weight and therefore has the greatest impact on the increased risk of gas accumulation. The calculated risk for groundwater pollution is modest and the risk of accumulation of gas at the landfill site is low. Since the depth of the groundwater table in this place is more than 22 meters, and its distance from the consumer is more than two kilometers, but because of the source near the landfill, the risk of groundwater pollution in this area is high.