نشریه هیدروژیومورفولوژی
پیاپی 36 (پاییز 1402)

Landslide, as an important natural hazards, causes damage to infrastructure and leads to economic, social and human losses. In this regard, determining the critical zones of landslides occurrence can be used in planning for damage reduction. The aim of the current research is analyzing and identifying landslide hot spots using Getis-Ord algorithm in Gharnaveh watershed, Golestan province. Therefore, the frequency and characteristics of landslides has been analyzed in different classes of slope, aspect, soil and land uses. The area, length, width, depth and height of the precipice of landslide features have been considered as the basis in hot spot analysis. The results showed that the landslide hot spots are located in the eastern part of the study area, which includes high altitude classes, rangelands and moderate slopes. Results showed that the rangeland and forest land uses, loess soils and 50-75% slope class and the northern aspect had the highest number of landslides. Also, the non-significant landslide points using the Getis-Ord method and considering landslide area criterion located in the middle and downstream of Gharnaveh watershed. Determining the landslide hotspots and affecting factors through the spatial analysis in GIS provides the defining thresholds in the landslide’s occurrence. The analysis of the landslide hotspots can be a basis for spatial planning, and risk reduction. The implemented approach can be used in the evaluation of the spatial autocorrelation of natural hazards, and in combination with the areas prone to multiple environmental hazards can predict the risk and severity of damages in the future.

Glacier cirques show the characteristics of past glaciers and climates. In this research, the analysis of 39 glacial cirques in the catchment area of Jajrud River was done. For this purpose, Arc GIS software and Google Earth images were used. The parameters of length, width, height of the top of the circus, height of the floor of the cirques , area, perimeter, ratio of length to width, ratio of length to height of floor and ratio of width to height of floor were used to check the morphometry of cirques. For each of the morphometric parameters, statistical factors of coefficient of variation, standard deviation, average, maximum and minimum were calculated and estimated in Excel. Then R2 values or coefficient of determination were estimated for each of the parameters and a scatter diagram was drawn. Finally, the correlation matrix was estimated using the Pearson correlation coefficient for all factors. The highest abundance of cirques is located in the southwest direction. The maximum height of the cirques is 3800 meters and belongs to the geographical direction of the south.The highest correlations between length and width parameters were observed at the rate of 0.9936. The results show that the cirques in the north-facing slopes have a lower height. This indicates the high nutrition of these cirques and their significant volume in the Pleistocene period. Investigations showed that more developed cirques have more area, less height and less length to width ratio than less developed cirques .

In the current research, to investigate the future climate of the Urmia Lake catchment, the maximum and minimum temperature, rainfall and drought in the basin were projected for the period of 2015-2099 using NorESM2-MM climate model under the scenarios of SSP. The downscaling output of the model was done using the quantile mapping method and their accuracy was evaluated in the simulation of the base period (1990-2014) using the monthly diagram and RMSE and NRMSE indicators. The evaluation of the results showed that: the minimum and maximum temperature of the basin under the pessimistic scenario (SSP5-8.5) until the end of the century and under the optimistic scenario (SSP1-2.6) until 2075 have an ascending trend and then a descending trend. Average maximum and minimum temperature of the basin in the near future (1.0 to 1.8) and (1.1 to 1.8) ℃ and in the far future (1.5 to 4.8) and (1.3 to 4.3) ℃ will increase. The annual rainfall in the future period does not have a significant trend, but the average rainfall of the basin in the optimistic scenario will increase by 16.5% in the near future and 8.9% in the far future and in the pessimistic scenario will increase by 1.8% in the near future and 7.2% in the far future. According to the SPEI index, in the future period, under the optimistic scenario, moderate drought will have an ascending trend, severe drought will have a descending trend, and under the pessimistic scenario, the drought will have a descending trend.

Alluvial fans are among the areas prone to geomorphological hazards. One of these hazards is liquefaction, which the main purpose of this research was to investigate this phenomenon in the surface of the alluvial fan. The FUZZY-VIKOR combined model and GIS technique were used to prepare the liquefaction risk potential map. The used parameters in this research were: slope, depth of underground water, type of soil and seismicity. The information layers of each of these parameters were prepared in the ArcGIS software environment. Next, the fuzzy model was used to standardize the layers. At the end, the weighting of the parameters was done by Vikor method. . The results of weighting the parameters by Vikor method showed soil and depth of underground water have obtained the highest importance coefficient with the weight of 0.442 and 0.236 respectively. The final map was prepared by overlapping the layers and multiplying the final weight of the criteria in each layer in 5 classes from very low to very high potential. The final map was prepared by overlapping the layers and multiplying the final weight of the criteria in each layer in 5 classes from very low to very high potential. The results of examining the area of each risk class showed that 0.28% of the area is in the very high class and 70% is in the high class in terms of the risk of liquefaction. Mainly, the areas with high risk potential are located in the downstream parts of the region.

AbstractSoil erosion is one of the most important problems in the watersheds of Iran, which causes the loss of thousands of tons of arable soil every year. The aim of the present study is to zoning the risk of soil erosion in Givi Chay watershed (northwestern Iran). In this study, first, the effective factors for erosion in the region were identified and then the information layers of each criterion were prepared in Geographic Information System (GIS). Valuation and standardization of layers was done using fuzzy membership function and criteria weighting, using critic method. Final analysis and modeling was performed using the Multi-Attributive Border Approximation Area Comparison (MABAC) method as one of the Multi-Criteria Decision Making (MCDM) methods. According to the results of the study, slope, land use, soil and lithology had the highest weight coefficient, respectively. Also, the results of the study showed; 283.89 and 414.93 km-square of the area, respectively, has a very high and high risk potential, and very high-risk and high-risk areas in unstable and erodible formations, agricultural uses and gardens and slopes of 25-40 % are located. It can be said that the results of this study indicate the high potential of the study basin in terms of erosion occurrence and it is necessary to control erosion and conservation measures on the agenda of experts and land managers. In addition, the results of validation of the results showed that the use of MABAC method has a high relative accuracy for studying the risk of erosion.

Therefore, the purpose of this research is to investigate and analyze the most important factors involved in creating the risk of subsidence in the Ardabil plain and to identify the susceptible surfaces that are likely to be involved in subsidence in the near future. The purpose of this research in the first stage is to evaluate the subsidence using radar interferometry technique in the Sarscape software environment, using the capabilities of A1 Sentinel images in the time frame of 2016 and 2021, and also in the following, in relation to the zoning of susceptible areas with the algorithm Aras multi-criteria was implemented in Edrisi software environment. The results of the present study showed that between 0 and 22 mm of subsidence has occurred in the studied area, and the highest amount of subsidence is concentrated in the central part and then in the eastern and north-eastern parts. According to the results of subsidence risk zoning; The criteria of water level drop, distance from the river, geology, and land use are the most important factors involved in creating the risk of subsidence in the study area, respectively, with a weighting factor of 0.221, 0.166, 0.152, and 0.147, respectively, and 267/41 and 403/21 square kilometers of the range have a very high probability of danger. Finally, it can be said that the most important factor involved in increasing the amount and potential of subsidence in the Ardabil plain is the excessive use of underground water and the drop in the water level.

Neglecting coastal erosion can lead to environmental hazards that are among the main factors affecting human communities and facilities. Paleontology researches demonstrate tens of meters fluctuation in water level of the Caspian Sea. The shores of the Caspian Sea have variable topography and land use including lowlands (estuaries of rivers, gulfs and progradation) and sandy uplands. In this study, spatiotemporal analysis was used to analyze the changes in sandy coasts in relation to land use changes and the adaptation of the coastal line in the study area within the framework of coastal cells. Land use data for the years 1975 and 2020 were extracted using SAGA and ENVI software, and land use changes were analyzed using IDRISI software. The results showed that 68 kilometers of the coast have been unstable, with the majority of these areas experiencing erosion due to human activities (land use changes), including cells 10 and 3. Also, the erosion of unstable cells 5, 6, and 1 is of natural erosion type (sea level changes), and the erosion of unstable cells 9 and 2 is of natural-human erosion type. The remaining 24 kilometers of the studied coastline have been stable coasts, with the majority of coastal areas experiencing natural erosion (sea level changes), including cells 7 and 8. Cell 4 has had sustainable coasts with erosion of a natural-human type.

Floods are one of the most destructive natural disasters that cause huge and frequent human losses ,financial and resource losses all over the world(Mishra & Sinha, 2020,1). Flash floods are caused by heavy rains and due to the sudden accumulation and release of runoff from upstream to downstream. This natural phenomenon is the result of the activity of two groups of different parameters. The first group is the meteorological features that change according to space and time. The second group of fixed parameters includes geomorphological and geological characteristics(Youssef et al, 2011,755).Therefore, identification and zoning of areas prone to flood risk is necessary for sustainable development planning and protection of human societies(Farhan & Ayed, 2017, 719). The Ojan Chai basin, which has been flooded in recent years, especially due to human intervention in basin system. One of the most unprecedented floods occurred in this basin in 2016. Therefore, according to the history of flooding in this basin, it is necessary to assess and zoning the risk of sudden flood. The aim of the current research is to evaluate and zoning flash flood-prone areas in the basin based on physiographic characteristics, which is the basis of the modified flash flood potential index (MFFPI).