نشریه جغرافیا و مخاطرات محیطی
پیاپی 48 (زمستان 1402)

In recent years, the mutual impact of land use change and soil erosion has become a major environmental concern. Therefore, this study tried to investigate the changes in different land uses and evaluate the impacts of land use changes on soil erosion in Givi city. To achieve the goals of the research, first, a land use map was prepared using the object-oriented method for the two periods of 2000 and 2021. Then, according to the natural and human conditions of the area, other effective factors for erosion in the area were identified and the information layers of each of the criteria were prepared by the geographic information system. Evaluation and standardization of layers were done using the fuzzy membership function and weighting of the criteria was done using the CRITIC method. The final analysis and modeling were done using the MABAC method as one of the Multi-Criteria Decision-Making (MCDM) methods. The results showed that the largest area in 2000 is related to good and medium pastures, recording 313.172 and 283.144 square kilometers, respectively. In 2021, the biggest areas are related to poor pastures and barren lands, with 335.077 and 329.815 square kilometers, respectively. According to the 2000 erosion zoning map, 16.34% and 20.36% of the city and according to the 2021 erosion zoning, 22.92% and 25.58% of the city’s area are in very high and high erosions, respectively. Decreasing good and average pastures and lands with dense vegetation and turning them into agricultural areas, poor pastures, and man-made and barren lands have had the greatest impact on soil erosion.

Protected areas are among the most important and effective areas in the world that have been established to protect biodiversity. The use of international methods in the management of protected areas will make it possible to achieve sustainable development along with maximum protection of biodiversity. Arsbaran protected area is one of the most valuable natural resources of Iran in terms of plant and animal species and one of the nine biosphere regions of Iran. This descriptive analytical study was done to evaluate the vulnerability of Arasbaran protected area using the DPSIR model and to provide management solutions. Using the DPSIR model, driving force, pressure, situation, effect and response, threats and values of the region and the relationship between them were investigated and evaluated. Then, strategies were presented in the form of possible responses to each of the components of the DPSIR model. Eight main driving forces are population growth, tourism development, development of communication routes, animal husbandry activities, development of rural settlements, development of agricultural activities, Songun copper mining factory, and lack of coherent management for the identification area. Considering them, the pressures, situation and effects of the region were identified. The results showed that in Arsbaran protected area, the greatest impacts of regional threats on ecological values, including the loss of shrubs and trees, wildlife habitats, and the reduction of biodiversity and cultural values, are being subjected to the supports of UNESCO Environmental Protection Organization and placed at the disposal of the Human and Biosphere Program. They cause the most intensive damages to the region in terms of vulnerability, destruction and change of land use, deforestation and animal husbandry. At the end, management strategies for facing threatening factors were presented.

This study analyzed the trust network among the forest and pasture users of  Naghareh Koub village in Ghaleh Shahin watershed of Sarpol Zahab Township. Parallel mixed method was used for this study. The statistical population was forest and pasture users of Naghareh Koub village, Ghaleh Shahin watershed, Sarpol Zahab Township (534 people), who were randomly selected according to Karjesi and Morgan’s table (223 people). Then, using the whole network approach and the snowball technique, 39 users were selected. Structured interviews and network analysis questionnaire were used for collecting the data. The indices of density, size, transmission, ambidexterity, centrality and concepts of intersection points and structural holes were studied. The data were analyzed using UCINET and NetDraw, and SPSS software. The results showed that the level of trust among local users was an average level, and among the types of trust, communication trust and procedural trust were more than other types of trust, and the lowest type of trust was dispositional trust. In the trust network with low density, the stability of the network (reciprocity) is average and fewer people are connected through intermediaries (weak transmission); therefore, the balance of the network is weak and information circulation in the network is medium to low. The results confirmed the high percentage of concentration in internal links compared to external links. Therefore, it is necessary to effectively manage conflicts in this area by forming a balanced and stable network of trust and considering key actors.

In recent years, studies on children’s perception and knowledge of risks and strengthening their preparedness against risks have increased. This can be due to the change of disaster management approaches from the passive approaches of the past to efforts for pre-danger management and the increasing influence of the readiness of all groups and strata of a society, including children. This study evaluated and analyzed the level of awareness of children of the danger of earthquakes in the form of variables of recognizing the risk and its causes and effects, and how to face it in the form of the variables of awareness of preventive measures, preparation and optimal methods of response among 169 children of 5 to 12 years old in Zirkouh, South Khorasan province. Questionnaire and interviewes were used for collecting data. The findings showed that the average level of awareness and knowledge of risk management among rural children is very low and needs to be improved. The results of the single-sample t-test in evaluating the average awareness and knowledge of risk management in all four measured dimensions are lower than the average value level. Moreover, the results of the correlation test showed that there is a significant positive relationship between the perception and awareness of the nature of the earthquake with the knowledge of risk management regarding the four dimensions.

The risk of wildfire in Iran has increasingly become a serious risk throughout the year and is no longer limited to a few months of the year. Accordingly, forest monitoring for identifying areas prone to fires is an effective step for the development of early warning systems. This research was conducted to see the relationship between the vegetation indices with the occurrence of fire in the vegetation areas of Iran. The MODIS sensor data of the Terra satellite, including the active fire product (MOD14A2) and vegetation indices NDVI and EVI (MOD13A3) were used from 2001 to 2020. The results showed that the maximum occurrence of wildfire in the vegetation areas of Iran occurs from the end of spring to the beginning of autumn. The increasing trend of wildfire occurrence in the warm period of the year is related to the increase in temperature, decrease in humidity, and early melting of snow in the spring season and the autumn season, simultaneously with the fall of vegetation and the late start of autumn precipitation. The maximum average height of wildfire occurrences in the Arsbaran vegetation area is 1791 meters in October and the maximum height of wildfire occurrences in the Irani-Turani area is 1565 meters in August. Spatial distribution of NDVI and EVI indices showed that the density of vegetation is effective in the intensity and spread of wildfire and provides the conditions for the spread of wildfire in such a way that barren areas with low vegetation cover the center, east, and southeast of Iran. Almost no wildfire occurred and the maximum number of active fires was observed in the north, west, and northwest of Iran.

Among natural hazards, floods are of special importance in terms of financial and human losses. According to available statistics and information, flood damage in most parts of the world, especially in developing countries, is the the most distructive and generally makes socio-economic and environmental damages. So, efforts for reducing the damage are the duties of related agencies. Estimating and determining the maximum amount of flood is one of the first steps for reducing its damage. Therefore, providing a definition of it is a fundamental step. In this regard, the selection of the maximum possible flood plays an important role. By definition, the maximum possible flood is the largest flood that can reasonably be expected to occur in a particular region and time  (World Meteorological Organization, 1986). Frequency analysis is one of the reliable methods in flood estimation if there are sufficient statistics and it is possible to fit a suitable distribution function. This method, which uses a complete statistical series (all available data), often uses normal statistical distributions, normal logs, three-factor normal logs, limit values distribution, Pearson, Pearson logs, and WebStud program (13). The purpose of frequency analysis of events in hydrology is to obtain the maximum probability of occurrence of values. The selected area for studying the geomorphic basin of Shiraz is in the sections of Aliabad, Maroon, Eghbalabad, Chenar Sukhteh and Bagh-e-Safa stations. In this study, long-term precipitation statistics in the rain gauge station of Shiraz geomorphic basin over a period of 50 years and maximum daily discharge statistics in a period of 44 years were used.

Flood is one of the natural disasters that can threaten economic, social and environmental sustainability activities. Therefore, identifying flood-prone areas in the basins is essential. The aim of this research was to prioritize and analyze flooding potential in Ghamsar watershed using multi-criteria decision making models and fuzzy logic. For this purpose, first, 14 effective criteria on basin flooding (including precipitation, elevation, land use, soil texture, lithology, distance to river, slope, drainage density, stream order, Topographic Wetness Index, Stream Power Index, flow accumulation, plan curvature, profile curvature) were identified. Rhen, pairwise comparisons were made between the criteria using the AHP method in Expert choice 11 software and the final weight of each criterion was obtained. Moreover, the criteria were fuzzified using linear and large fuzzy functions, and finally, the final weights obtained for each criterion were applied in the respective layers and the final flood risk map of the basin was prepared. The results of prioritizing quantitative and qualitative criteria based on the opinion of watershed management experts using the AHP method showed that among the 14 proposed criteria, the precipitation criterion with a final weight of 0.229 has the most impact on the flood risk of the basin. Moreover, the criteria of heavy to very heavy soil texture (0.499), Plvav stone unit (0.252), water areas and bare lands with final weights of 0.345 and 0.225, respectively, have a stronger role in the flood risk of the basin. The results of the final flood risk map of the basin showed that about 30.841, 27.056 and 12.406 percent of the total area of the basin are in the medium, high and very high flood risk categories, respectively, and these areas are located mostly in the central part and along the southeast of the basin. Therefore, knowing flood potential of the basin can be effective in formulating crisis management plans when faced with floods.

Asignificant amount of the damages caused by floods is usually due to suspended sediments in the flood and dredging costs due to their subsidence in natural, residential and industrial areas. Therefore, sediment monitoring is very important when the water discharges. On the other hand, the non-linear nature of sediment data have made it difficult to predict this parameter. Wavelet theory is one of the pre-processing methods that can help we lead to a better resolution of the internal relationships of non-linear data by breaking down the main time series into sub-signals. I this research, the sediment data values in two stations of Abnama and Minab from Hormozgan River watershed were broken through wavelet conversion into sub-signals, and then the prediction process was carried out by the artificial neural network. Moreover, in order to investigate the impact of wavelet transform on the performance of the neural network model, the results obtained from this combined model were compared with the results obtained from the single neural network model, and their efficiency was evaluated using multi-part validation method, correlation, and root-mean-square error. The results showed that the artificial neural network in the two studied stations is able to simulate the sediment discharge with a correlation of 0.89 and 0.68 as well as the wavelet neural network with a correlation of 0.9 and 0.8. Moreover, the normalized root-mean-square error statistics were 0.104 and 0.35 in artificial neural networks and 0.124 and 0.18 in combined networks, respectively. The results showed that the impact of the wavelet on identifying sub-signals and thus improving the performance of the model compared to individual neural networks on predicting the amount of sediments in floods is clearly significant.

Changes in precipitation patterns and its intensity due to the global climate change has led to intensifying floods as the most occurent natural disaster. ‏Flooding cannot be fully prevented, but its impacts can be mitigated by accurately identifying flood-prone areas and implmenting appropriate risk-based management measures. The Qarachai Watershed, located in the upstream of the Gorganrood River Basin in Golestan Province, Iran, was chosen as the study area, which has experienced several flood events in recent decades. ‏In this study, flood risk was assessed using the HEC-RAS, a two-dimensional hydraulic model. ‏Flood discharge values occured in the early 2019 were considered as model input, and based on ground truth, the manning roughness coefficient values were measured. To evaluate the results of the HEC-RAS model, some statistical criteria were used reflecting a good performance of the model. ‏The analysis showed that by increasing the return period, the extent, depth, and amount of flood risk increase. Moreover, the analysis showed that the flood zone in 100 year return period, affects parts of Seyedkalate Village. Approximately, half of the flood zone identified in this study was attributed with very low-risk. The results of the study are used to adopt appropriate strategies and plans to adapt to climate change and as an appropriate tool for identifying flood exposed and flood-prone zones.

Nowadays, heavy rains are an important aspect of climate studies because of their dangers and damage. Cut-off lows are influential in the occurrence of heavy rainfall in Iran by creating atmospheric instability. In this regard, first, the climatic variables of temperature, precipitation, and geopotential height of 500 hPa were investigated in connection with the formation of cut-off low during the period 1986-2018. Then, to predict the changes of the cut-off low event in the future and its impact on heavy precipitation, ECMWF database ERA-Interim version and CMIP5 models with CORDEX exponential microscale approach under two scenarios of optimistic release RCP4.5 and pessimistic RCP8. 5 was used until 2099. The results showed that in the RCP4.5 scenario, the increase in precipitation was estimated to be at least 2.41 mm, and in the RCP8.5 scenario, the maximum precipitation decrease was estimated to be 91 mm. The surface pressure anomalies of 500 hPa will increase by 61.5 and 92.5 geopotential meters based on RCP4.5 and RCP8.5. The lowest frequency cut-off low events was in 1995 and 1996 with 10 events, and the highest event was in 1986 with 30 events. With the increase of air temperature and the advance of subtropical high pressure towards high latitudes, the place of formation and the path of movement cut-off low in 33 years have been extended towards northern latitudes, which indicate the effects of change of the climate in Iran. The existence of a significant positive relationship between the frequency cut-off low events and heavy rainfall was confirmed at the 5% error level. Moreover, the impact of cut-off low on the frequency of heavy rainfall in Iranian stations, especially the northern stations, has been more impressive.

Soil deformation can have a major impact on the seismic design inputs of structures. In practice, the soil is always bounded by rocks. In this case, the phenomenon of resonance or beating due to the closeness of the frequency of the structure to the natural frequency of the soil can be very destructive. For this reason, the natural frequency of the soil is considered in the construction regulations in presenting the spectral shape. To determine the natural frequency of soil in Behbahan city, the H/V method based on non-destructive measurement of ambient noise, which is a inexpensive and successful method for evaluating soil properties, was used. After recording microtremor data in 69 stations, H/V analysis was done to estimate the resonance frequency at the points. Then, natural frequency maps of the soil were presented. The results showed that the natural frequency range of soil in Behbahan city is between 0.57 and 5.42 Hz. Therefore, this soil is included in soil types 2 and 3 (standard No. 2800). Moreover, based on the construction information, a resonance-prone areas map was provided. In the central areas, the soil type is mainly type 3. Most of the buildings in this area are low codes, so it requires more precision in future developments. In the northwest and southeast of the city, the period of soil resonance is more than one second; therefore, in the construction of tall buildings in these areas, more strict measures should be taken into account to control the structures.

Mass movements of materials are divided into slip, flow and creep, among of which landslides always cause heavy financial and economic losses worldwide. In this study, based on the analysis of landslides in Shahroud Basin, effective vectors were rated. Using ArcGIS software, the spatial distribution of 183 landslides in Shahroud basin was analyzed and interpreted in fault, waterway, road, lithology, slope, aspect, precipitation amount and height. According to the effect of different vectors, and the spatial distribution of landslides in Shahroud basin, points were scored and entropy matrix was adjusted for them and landslide occurrence in Shahroud basin was zoned. Based on the results of applying Shannon entropy model in Shahroud basin for landslide zoning in terms of landslides, high-risk zones accounted for 41.79% and an average of 52.76% of the basin area. The adaptation of landslide risk zones of Shahroud basin shows the concentration of 74.86% of landslides on slopes of 10-40°, 64.97% in marl, conglomerate, and basalt lithologies, 87.97% at altitudes 2123-823m, 85.79% in semi-arid and temperate rainfall classes (685-315mm) on land surfaces with slope in the western direction, 55.74% at a distance of 0-300m from the river, a distance of 0-500m from the fault and at a distance of 1000-500m from the road. The concentration of danger and landslide zones in the two central parts of Taleghan subspecies and after the joining of Alamut and Taleghan rivers and the formation of Shahroud River is more than other areas. Such changes in landslide distribution due to nonlinear compliance of this geomorphological event are influential factors. The occurrence of landslides is a function of the interaction between factors rather than their abstract effects.

Tectonic factors play an important role in landform changes in the regions. Based on these changes, the tectonic state of the regions can be assessed, so analyzing the tectonic status of landforms for environmental management and various planning is important. Accordingly, in this study, the tectonic status of anticlines in the northern and western regions of Kermanshah province, Iran, and its relationship with seismic centers were investigated. Digital 30-meter SRTM model, 1: 50,000 topographic maps, 1: 100,000 maps of the region, as well as the information on the epicenter of earthquakes that occurred in the region during the years 1900 to 2020, were used as research data. This research was done in three general stages. In the first stage, using 8 geomorphic indices, the tectonic situation of 5 anticlines of Ezgeleh, Daneh Khoshk, Sanjabi, Mahidasht and Vis was analyzed. In the second stage, the location map of the seismic centers that occurred in the region during the years 1990 to 2020 was prepared. In the third stage, the relationship between the tectonic activity of the anticlines in terms of different indicators and focal points of the earthquakes that have occurred, was evaluated. Based on the results, the anticlines of the western regions (anticlines of Ezgeleh, Daneh Khoshk) have a more active tectonic status than the anticlines of the eastern regions. Moreover, considering that the western parts of the region had the highest number of seismic centers, so it can be said that there is a direct relationship between the seismic centers and the tectonic position of the anticlines.

Bidvaz dam drainage basin is located in the northwest of Esfarayen, which is geologically a part of Aladagh-Binaloud structural zone. For managing water resources and optimal use of these resources, a dam has been built on the main branch of this river. By pouring water into this dam, it became clear that water escape from this dam is more than the existing standards. The subsequent measures for reducing water leakage from this dam did nor result in positive consequences. Although the construction of this dam has had many benefits to the region, the increase in water leakage made the people living downstream worry. The high leakage of water from this dam evokes the assumption that the escape of water may be caused by tectonic activities. Because the lives of more than 70,000 people, including the people of Esfarayen city and several populated villages, are closely related to the water of this dam, it was necessary to study the tectonic activities under its basins. In this research, which was conducted using morphotectonic indicators and with the aim of identifying tectonic activities in this dam, it was determined that the region is tectonically in the ranks of active regions. Evidences such as the activity of faults, the study of earthquakes in the region, the results of morphotectonic indicators, and the study of profiles of the sub-basins of this river all indicate that this basin is tectonically active. Therefore, more attention should be paid to the operation, maintenance, and technical aspects of this dam.

Morphometric indices are widely used as a tool for identifying and characterizing the deformed sections by active faults. So far, the relationship between active tectonics and morphotectonics has not been studied in the studied area. By determining active processes in the Klardasht and Abbasabad basin and taking the necessary measures, it is possible to avoid damages caused by natural hazards such as floods and earthquakes in this area. In this study, using morphometric indices, the basins of a part of Central Alborz were investigated in terms of the influence of active tectonics. So, the Klardasht and Abbasabad basin was analyzed using Hierarchical Anomaly Index (∆a), Longitudinal River Gradient index (SL), Form Factor Index (Ff), Drainage Density Index (Dd) and Relative Prominence Index (Bh) in 18 drainage basins of the specific area. Along the North Alborz, Khazar and Azarak faults, the amount of these indicators increased. So, it can be concluded that the tectonics of the studied area is active due to the activity of these faults. Finally, by determining the Relative Active Tectonic index (Iat), the region was zoned into four categories (very high, high, medium and low) in terms of the level of tectonic activity. In about 66.5% of the region, which is dominated by the activity of the main faults in the region. Other sub-faults formed by recent tectonic movements show moderate to high tectonic activity.