نشریه هیدروژیومورفولوژی
پیاپی 23 (تابستان 1399)

Today, geomorphic studies are considered as the base of studies on natural resources. Recognizing the processes and active mechanisms on these landforms and their characteristics, as well as understanding the type of use of these units in using the natural environment and sustainable development is important. Many of Iranian towns and villages are on plains and alluvialfans and as a result, exploitation of the plains has become diverse and growing; but there are problems and limitations in the use of these areas. For a successful farming, consideration of climatic and environmental conditions is of tremendous importance. Therefore, the designation of geomorphic units is a suitable method for detailed studies of natural resources planning and management and environmental hazards. According to some experts, the assessment of environmental power is an instrument for identifying a land for activities such as agriculture and forestry (Quang minh et al, 2003). The agricultural sector of Sanandaj Province is especially important among the economic sectors of the province since in terms of production and employment, it is ranked second after the services sector. The geographical and climatic conditions and abundant water resources provide the potential benefits of agricultural production in the city. In  recent years, with the adoption of new software and hardware methods, many efforts have been made to determine the capability and management of land leading to fruitful results.

The purpose of this study is to assess land suitability for agricultural activities in Sanandaj based on hydrogeomorphological parameters. To this end, the research method is based on descriptive-analytic methods. Research data includes statistical information (information on the status of groundwater and climate parameters), information layers, information extracted from satellite imagery (land use), as well as library information. Software used in the research includes ARCGIS (providing information layers, fuzzy, final output), IDRISI (implementation of the OWA model), Google Earth (validation of results), and SuperDecisione (weighting to criteria). The data layers of this research are soil, land type, geology, slope, altitude, precipitation, river, temperature, groundwater status, and groundwater chemical quality. Since the value and importance of the parameters are not the same for the desired purposes, the parameters were evaluated using expert opinion (5 geomorphic experts) by the ANP method and fuzzy by using the fuzzy function in ArcGIS software. Afterwards, standardized layers are entered into the IDRISI software and then combined with the ANP model using the OWA model based on the obtained values. Finally, the final map is made. After drawing up the final map to verify the results, 50 random samples were used to validate the result.

In this research, ten parameters have been used for the development of agricultural lands in Sanandaj. The parameters are assigned in three clusters: Geomorphologic parameters (elevation, slope and geomorphology units), hydroclamite (river, underground water, chemical water quality, temperature and precipitation), and land cover (soil and lithology). In this research, after providing information layers, these layers are standardized using ARCGIS software. The  geomorphological parameters are standardized in such a way that the altitude, the lower height means that the pixel is worth more And also in terms of slope, areas with a lower slope are worth more. In terms of geomorphology units, the lake and mountain units are of the lowest value. In terms of hydro-climatic parameters, regions with higher rainfall and temperatures near the river have lower groundwater depths and areas with lower EC values ​​are of higher value. In addition, the areas with inspetisol are of higher value and lithologically, the areas with alluvial lithology are more valuable. The value of the criteria was then calculated using the ANP model. Finally, the obtained value was applied to the layers and in the end, using the OWA model, the final map is obtained.

Since agriculture makes a major contribution to the economy of Sanandaj, and given the great potential of the city in terms of water resources, it is necessary to make proper planning and location in this area. In the present study, according to studies conducted and hydrogeomorphological survey related to the study area regarding zoning the area for the development of agricultural lands, it has been attempted to identify suitable areas for the desired purposes. The results of zoning using integrated network analysis and sequential weighted averaging model have been verified using integrated network analysis model and random sampling method is verified. The confirmed results indicate that the final map has 86 percent accuracy. The results of the present study indicate that the major part of Sanandaj does not have the proper level of agricultural activities so 1587 km2 of the city area is in the inappropriate class and the relatively suitable and suitable class area is 801 and 579 square kilometers, respectively. According to the results, about 53% of Sanandaj area is not suitable for agricultural activities, especially for water crops.

Instability of natural slopes is one of the geological and morphological phenomena that has a significant role in changing the form of surface of the earth, and when it affects human activities, it can become a dangerous phenomenon (Esfandiari, 2006: 113). Landslides as geological events related to the transportation of soil / heavy rock materials and assessment of its sensitivity, is an important task for local authorities to plan and reduce the land (Xialong Deng, 2017: 2). Therefore, many attempts have been made to assess the dangers of mass movements, and it is suggested to have its reduction methods based on the key characteristics of the slip, including scope and extent, volume, startup mechanism and recurrence, and subsequently, make decisions (Kuo Jeong Chank et al., 2018: 700). (Hemati and Hejazi 2017: 24-7) evaluated the landslide hazard zonation of Lavasanat watershed using logistic regression statistical methods and the result was stated in this way that in the studied area, areas with high risk of zoning, had a large share of the area amount of ​​the region.  Aliabad basin with the southwest - northeast trend in the geographical coordinates of -   located in the east and - located in the north latitudes of the northeast of East Azarbaijan Province and southeastern part of Horand County.(Figure1) Figure (1): Geographic location of Aliabad watershed

 Topographic map (1: 50000) and geological map of Kaleybar region (1: 100000). 2- Landsat satellite images of 8 OLI sensors 3- GPS devices 4- Maps of the faults, slopes, isohyet, isotherm, evaporation, land use, elevation and hydrology 5- Envi 5.3 software 6- Statistical software of SPSS, version 16. For zoning the risk of rock falls, nine layers of information including slope, hypsometry of the region, isohyet, isotherm, evaporation, distance from the fault, distance from the river, land use and lithology were used as independent variables and to prepare the layers in Arc GIS, 1,500,000 topographies and 1.100000 geology maps were utilized, and Landsat 8 satellite imageries were used with the OLI sensor to produce the land use layer. So, after preparing the considered data, the layers were classified as raster, and in their descriptive table, a column called the standard weight was added and the classes related to each layer were calculated using a sum ranking method. In this research, the rock fall layer was considered as the dependent variable and the 9 presented layers were considered as independent variables and all layers had been evaluated in the normalization of the weight between zero and one per pixel; based on the proportion table method, each layer, having 500 weighted pixels that overall included 5000 pixels, was entered into the SPSS environment and regression analysis was performed thereof. Independent variables, including 9 variables, consisting of three PhDs in geomorphology and two Phd in geology were selected based on exports opinions considering their importance in creating and strengthening the dependent variable were weighted between zero and one numbers.

The Chi square test for each of the independent variables, separately, showed that there was a significant relationship between the independent variables and the dependent variable, and the effects of these variables on the dependent variable was acceptable. The numerical value of R was 0.953, and if the R value was closer to one, it would indicate the high validity of the test. The numerical value of the coefficient of determination of the independent variables relative to the dependent variable was 0.909, which indicated the high validity of the significance of the test, because it was closer to number one. Of course, it is clear that the value of the determination coefficient in Pseudo R Square was determined to be good, so the adjusted coefficient of determination was considered whose numerical value was 0.907. These findings indicated that roughly 90 percent of rock falls occurred in the Aliabad basin have been affected by these 9 estimated independent variables. Given that the statistical analyzes confirmed the validity of the effects of independent variables on the dependent variable according to the weightings of the experts in terms of zero and one for each variable as well as the importance of the variables in relation to each other as a binary comparison, the zoning of the risk of rock fall for the Aliabad watershed of the Horand basin was done using Arc Gis software, and in this zonation, five falling risk classes were used including very high, high, medium, low and very low .

lithology and the distance from the fault and river and foot slopes were the most important factors in the formation of rock falls since the drainage system of the basin exactly followed the fault zone. The reason for this issue can be analyzed in the way that the longitudinal distance of the highest parts of this region, from the basin to the Aliabad River was lower, which has caused the slope of the basin to perform deep slices to achieve a balance in the slopes and hydrology. The southern parts of the basin are considered as one of the most susceptible basins in the geomorphologic phenomenon of rock falls and destructive cones due to the existence of alluvial formations and the lack of proper slopes and the relative reduction of the fault to the northern and eastern parts despite having significant heights and very low and low status of zonation in the risk of rock falls, and in the southwestern part of the basin, a presence of rocky outcrops in the presence of permeable cones has been also observed. This issue should be addressed to the authorities in order to avoid serious damages to the lives of the inhabitants of the basin, so that the potential risks of this phenomenon could be controlled as much as possible including: threatening communication routes and threatening rural villages and damaging electrical and telecommunication facilities, therefore, infrastructure solutions should be applied in this regard.

Due to the dry weather in Iran, water supply has been plagued by complex systems and requires comprehensive management, the sustainability of these biological systems. Iranians have used a variety of water transfer and extraction systems that were unique in their time and this regard, they have been thinking about the optimal use of groundwater harvesting techniques and promoting further education. Some of these methods are completely native and the same is not seen in other parts. Many of the current procedures and methods of human life are out of ecological ability and cannot be sustained. Therefore, methods and techniques are considered that are consistent with the ecological laws (Boozjmehri and Khatami, 2018: 123). A review of historical records shows that rulers and people were paying attention, drilling aqueducts as one of the main water supply methods in arid areas (Omidi et al., 2016: 34). Other methods are Rainwater and runoff collection that have been considered for the proper utilization of water in arid regions (Eshghizadeh, 2009). Other methods of water supply in arid areas include the transfer of water from rivers and inaccessible water sources (Halabian and Shabankari, 2010). The purpose of this study is to investigate and introduce an interesting traditional and native method of conveying water to a corner of Iranian land that interestingly drives water on the fan to be used for agriculture. In this research, while introducing this method, the benefits, disadvantages, and costs of ecosystems are investigated and introduced to keep indigenous methods in place, if necessary, to Resuscitate and promote them. The study area is located in the northern slopes of Jaghatai mountains, Nodeh Enghelab village of Khoshab county and 57 degrees 37 degrees and 54 seconds to 57 degrees, 37 minutes and 6 seconds east and latitude 36 degrees 29 minutes 45 seconds to 36 degrees And 27 minutes and 52 seconds north.

The present study seeks to investigate the Abravaneh in terms of method of construction, properties, advantages, and disadvantages by using descriptive - case and comparative study and using various documents and maps as well as various geographic software such as GIS. Information about the subject is gathered from library resources and various documents such as books, collections of articles, geological maps (1: 100,000), and topography (1: 50000) and internet resources such as Google Earth and valid websites. The materials were collected through observation of the area and interviews with the owners and owners of irrigated plots by Abravaneh and those who knew it.

The results of this study indicate that unlike the aqueducts, they have begun to dig deliciously from the upper reaches of the basin (entrance valley), therefore, the entrance valley and the main river, which is to be transported from it, is considered as the mother of the well. The differences between Abravaneh and aqueducts are given in the table below.

Several factors have contributed to the occurrence of the landslide that could increase the risk of landslide in any area. Identifying these factors and their value can help to appropriate landslide zonation. The aim of the study is to find ways to reduce the damages caused by them, which makes it necessary to zoning the susceptible areas that play an undeniable role in watershed management. Therefore, by using statistical models and assessing them, the sensitive areas to the occurrence of landslide are identified. In this research, the landslide hazard zonation was performed based on the data-driven method. Based on this method, the zoning was done based on the use of slope data, aspect, elevation, precipitation, vegetation, geology, land use, distance to fault, distance to river, and distance to road. To validate the model, the ROC curve has been used which is a new and efficient method for verification. The purpose of this research is to investigate various influencing factors that affect the landslide occurrence in the Nazlochai basin.

In the methodology section, the satellite imagery processing (to identify and extract landslides, vegetation extraction, and land use) and logistic regression model have been discussed for landslide hazard zonation. In this study, by reviewing the previous sources (Mir Nazari, et al., 1393, Abedini, et al., 1393, Ayalew, et al., 2004, Ebadinejad, et al., 2007) and by investigating various factors (morphometric, climatic, and human) in Nazlochai basin, ten effective factors (elevation, slope, aspect, distance to river, distance to road, distance to fault, lithology, landuse, precipitation, and vegetation) on the landslide occurrence in the area were considered. The ArcGIS software was used to digitize and provide information layers for landslide hazard zonation, and the ENVI software was used for image processing, vegetation extracting, and land use mapping. Existing landslides were identified and characterized using various tools including aerial photos, satellite imagery (Google Earth), existing information, Global Position System (GPS), and field surveys.

The obtained coefficients indicated that the occurrence of landslide in the studied area had a direct relation with lithology, slope, and aspect factors, and weak relation with landuse, distance to fault, precipitation and distance to river. Lithology investigation of the region indicated that the more landslides have occurred on calcareous and conglomerate stones, which could be due to the development of the slopes and the accumulation of destructive materials on them. Slope is one of the slippery factors due to gravity and decreasing shear strength of soil in slopes of more than 10% to 45% leads to instability which in most researches is considered as an effective factor, too. Also, north slopes are more susceptible to landslide than the southern slopes due to the reduction of normal pressure and shear strength of the soil. By considering the Pseudo R-square index (equal to 0.34), which is greater than the threshold (0.2), this model shows acceptable fit. The area under the ROC curve was equal to 0.958, which shows a strong correlation with predicted landslides by the logistic regression model. Finally, the study area was classified into 5 landslide hazard classes include very low, low, medium, high, and very high.

In this research, landslide hazard zonation has been done using the logistic regression model in the Nazlochai basin. The coefficients of variables indicated that the occurrence of landslide in the study area had a direct relationship with the lithology, slope, and aspect factors; and weak relationship with landuse and distance to fault. Thus this indicates the probability of landslide occurrence increases by changing in lithology, slope, and aspect

Floods have historically been the most common, deadliest and most expensive hazards among natural hazards. The risk of flooding has increased over time, especially since countries have allowed changes in the land uses and land coves in floodplains and plains. In Iran, like the other flood-prone areas of the world, the severity of floods and the extent of their damages have increased dramatically in recent decades. Land use and vegetation play an important role in the production of runoff due to its effect on infiltration, erosion, evapotranspiration and transpiration.

Khorrambid watershed having an area of ​​88.7 km is a part of the Sivand Dam watershed. The average rainfall of this basin is 228 mm and it has a semi-arid climate in the view of Domarten. Khorrambid metropolitan basin consists of 12 smaller sub-basins in the study area with three main waterways named A, B and C that cross the city upstream of Khorrambid and pass through the city. In this study, the design, purpose, and efficiency amount of the flood and runoff output amount have been evaluated and finalized from the hydrographic network. The set of Management, Biological and Structural works carried out in the Khorrambid urban basin of the Sivand Dam Branches include: management excavation, piling, seeding, Dry working forage, Dry Stone Structures, rock and PVC mesh, rock and earth dams. Detailed studies and implementation of Khorrambid urban watershed was carried out in 1999 and the implementation of watershed management projects started in 2002 and by the end of 2010 about 33% of the projects were implemented in the study phase. At the same time, the evaluation process regarding the effect of these projects on flood and runoff control took place. This study aimed to evaluate the performance of projects (management, biological and structural) on the runoff and water resources in Khorrambid watershed in Fars province. In this study, first, the height of the dams, the length of the reservoir and the slope of the canals were measured under the basins where structural projects were carried out to determine the route of the new water movement. Then the new concentration time was calculated using the Branse-Williams method. In the next step, soil cover layer data such as the percentage of canopy cover, hydrological groups and vegetation status were obtained to determine the number of curves and maximum holding and infiltration potential in the soil. Then using SCS method and Hyfa software, modeling the flood volume and outflow runoff for sub-basin were estimated.

By analyzing the results of statistical analysis of changes it can be said that there were many changes in all land use and land cover as well as the implementation of structural and biomechanical projects in the studied area. To investigate the effect of land use and structural changes on the hydrological regime of the studied basin, SCS method was utilized. This model was formulated using GIS techniques. The results showed that due to the increase in rangeland land use (from poor to good condition) and the construction of watershed structures, flooding in the area has decreased in case there were 24-hour rainfall. This amount of runoff reduction in the basin A and C was 41% and 72%, respectively.

It is suggested that by evaluating the projects, if the performance of these projects could be evaluated in appropriate ways and from various technical and engineering aspects, the results would lead to finding the causes of the proposed operation failure and presenting appropriate solutions to address them. On the one hand, this could improve the quality of implementation of watershed management activities, on the other hand, it would increase operational efficiency, and the learnt lessons would enhance future plans. On the other hand, it is recommended that since watersheds are in fact considered as a natural-human system as well as a planning and work unit, comprehensive management of these watersheds is essential for achieving sustainable development goals. Watershed management is a complex process whose practical goals should be in line with the promotion of stakeholders` interests and stakeholders` engagement at all levels of planning and decision making. Integrated Watershed Management requires a flexible process that taking into account the challenges and constraints of the Watershed System, makes good use of its opportunities and potential conditions to ensure the social and economic well-being of its stakeholders while maintaining the security of water, food and environment in order to meet its goals of sustainable development.

Rivers are dynamic forms of natural landscapes with different changes at different times and places. The effects of river adjustment caused by the natural factors require much longer span to reveal. However, sometimes the natural factors such as river floods, landslide, or earthquake can lead to canal adjustments in a very short time (Chaiwongsaen et al, 2019:153(. In contrast, human activities can have a significant and rapid impact on natural processes and trends, resulting in a short time scale for river adjustments (Rinaldi & Simon, 1998:57).  River canal instability plays a major role in erosion, destruction of beaches and riverbanks. This role becomes more significant when the canal and bed of the river is alluvial (Rezaei Moghadam, 2012:33). One of the key issues in studying the erosion and stability of rivers is the initiation of sedimentary particle movement. The motion of sediments occurs if the bed shear stress (available shear stress) induced by the flow exceeds a certain critical value. An alluvial canal, either artificial or natural, persists to deform its boundary by itself while transporting water and sediments. Therefore, erosion and riverbank instability have created major concerns worldwide over the past few decades and significant amount of money have been spent to sustain the riverbanks. Givi-Chay River which is almost 54 kilometers long, is one of the permanent rivers of Ardabil province, Iran; problems of bed and bank erosion are evident in different areas of this river and they damage agricultural lands and adjacent river installations. In addition, a review of the research shows that sufficient studies have not been carried out so far to reveal the stability, erosion and sedimentation process in Givi Chay River.Therefore, this study aimed to analyze and evaluate the erosion stability of Givi Chay River channel.

In this research, the topography map with a scale of 1: 50000, geology map with a scale of 1: 100000, and google earth and Landsat Eight images, including OLI sensor (2019), bedrock maps and the Givi-Chay River area at a scale of 1:2000 hydrological data from two Abegharm stations (upstream of the dam) and Firoozabad (downstream of the dam) and field data are used. In addition, to control the results obtained by quantitative methods, field studies are applied for confirmation and verification. ENVI 5.3, Arc GIS 10.5, Excel, and HECRAS software were also used for image processing and data analysis. The geomorphological parameters of the river and their variations including bending coefficient and central angle were measured. The curvature coefficient is one of the few criteria used in river shape segmentation using s=1/(y.2), i.e., by dividing the valley length by wavelength for each arc, it is calculated. The central angle of the arcs on each of the intervals was calculated using the relation A=180L / Rπ, where A is the central angle, R, of the fitted circle radius.The increased shear stress in the riverbed increases the load of the floor and the scour of the bed, which can affect the riverbanks as erosion, destruction, and rupture of the walls. Direct measurement of shear stress is a difficult task and therefore researchers have developed methods for indirect calculation of shear stress. Existing shear stress (boundary), lateral shear stress, and critical shear stress were calculated by means of equation 1, 2, and 3, respectively:  (1)  (2)  (3) Relative Stability Index Calculation (RBS):Judet has introduced this index as the ratio of critical bed velocity to actual bed velocity. Olsen et al (1997) defined this index as the ratio between the critical shear stress and the shear stress of the sides. Relative stability index (RBS) was obtained using the following equations:(4) (5) (6)

Investigation of the morphology of the intervals shows that in the first, second and fourth intervals the conduit is sinusoidal and in the fourth interval, the pattern is meandering. In addition, according to the results of the study, the first, second and third intervals are developed in a very meandering manner and the fourth interval is just a meandering one. shear stresses in sections 4, 3 (second interval) are more than other sections, and given the direct relationship between shear stress and depth and width of sections, even under current conditions there will be phenomena such as scouring and damaging river bank and rivers. In addition, in terms of critical shear stress, the highest shear stress is in sections 3 and 7. Due to the relative stability values, sections 5 and 7 are stable and other sections are unstable. In the first period, the river flows into a valley bed, and in parts formed by erodible formations and at sections close to the dam, the river width is approximately increased. Therefore, sections 1 and 2, which pass through alluvial terrace sediments, are in unstable condition. In the second interval and immediately after the Givi Dam, the river passes through the valleys overlooking the Givi town, where the width of the bed due to the types of the banks decreases and the riverbed contains coarse sediments  covered by broken rocks. In other parts of the city of Givi, erosion conditions prevail and large volumes of flanking material (especially during floods) are eroded and loose flanks lead to the widening of canals and intra-canal ridges, and these sediments are clearly visible in bends, middle islands and marginal lands and steep banks. At sections where the river width is excessive and the slope decreases, the stability factor is almost high (sections 5 and 7). At the beginning of the third period, Firouzabad area is located on path of the flood of the previous interval and by joining Sanghor Chay, the river enters the mountainous part and the coastal areas have deep valleys with steep slopes. Along the river, due to collision with high mountains and rocky outcrops, the alternate route has a meander and river changes are subject to valley changes, and the meandering state is seen throughout the valley. In the fourth period, the river width is reduced and the riverbed is covered with coarse sediments, which extends to Ghezelozan.

According to the study results, in the plain interval, the main factor affecting the river meandering is the alluvial formation; here, the slope is low and the meanders are inscribed and plain, whereas in the mountainous part, the river changes are subject to valley changes and the meandering state is seen throughout the valley. According to the values of shear stress, the lowest boundary and bank shear stress is in sections 5, 6 and 7 and the highest is in sections 4, 3, 11 and 12. The highest critical shear stress is in sections 3 and 7 and the lowest is in sections 4, 2 and 12. The study of the relative stability of the river shows that the river is more unstable in sections crossing the old and new alluvial terraces, and in sections where the river width is high and the bed slope and flow rate have a decreasing trend, the coefficient of stability is relatively high. The third and fourth intervals are mountainous and semi-mountainous, respectively. In these intervals the river width is small and there is no agricultural land use .Lithologically, most of the third and whole of the fourth period consist of Eocene igneous and pyroclastic formations and they are resistant to erosion and the existing alluviums are the result of transport of water from sediments of other intervals.Therefore, the morphology of the river is affected by lithology and according to field evidence, the interval is stable .But the results of using mathematical and experimental methods have introduced the third and fourth intervals as unstable . Therefore, it can be acknowledged that the methods used in this study apply to the study of stability in rivers and alluvial intervals

The effects and evidence of tectonic activity can be seen in most parts of the planet; particularly if these activities have occurred during the Quaternary period and thereafter, the evidence would be readily recognizable (Guarnieri and Pirrotta, 2008:264). Iran is tectonically an active region. Many indices have been developed, tested and validated for quantitative geomorphic analyses to identify topographic fingerprints of surface and sub-surface processes. Morphometric analyses of river networks, drainage basins and relief using geomorphic indices, as well as geostatistical analyses of topographical data have become useful tools for investigating landform evolution. GIS platforms and high-resolution digital elevation models (DEM) facilitate the computation and charting of this type of information (Hayakawa & Oguchi, 2009:31). The stream length gradient index (SL), describes the morphology of the drainage network using a topographic gradient along a river. This index is sensitive to tectonic and lithology activities and is used as an indicator for tectonic areas. In this study, the morphometry of the catchment in north of Damghan was estimated and their stream – length gradient (SL) indexes have been mapped using GIS.

The studied area is located in northern mountain range of Damghan (East Alborz). In order to study the morphometry and tectonic indexes of the area, geological maps (1:100000), topographic maps (1:25000), and DEM 12.5m were used. The computation of SL was based on the interpolation of a discrete value. For a segment of a given river, the SL has been defined as: SL= (ΔH/ ΔL) Ltc. where ΔH is the variation of elevation, ΔL is the length of the segment, and Ltc is the total channel length from the midpoint of the segment where the index is calculated from upstream to the divide; actually, (ΔH/ΔL) is the slope of the considered segment. The drainage network was automatically delineated from the DEM, and SL was computed using ArcGIS 10.6®with the Spatial Analyst® extension, supported by several freeware packages including Arc Hydro Tools and ET Geowizard. The obtained point dataset of SL was interpolated using the ordinary kriging (OK) algorithm to estimate the spatial distribution of SL for the whole river basin.

Geologically, the studied area is located on the southern slopes of Eastern Alborz. The southern parts of the area are located between the two structural units of Alborz and Central Iran. This has caused the complexity of this part, lithologically and tectonically. A large part of the studied area consists of the Mesozoic formations, especially Jurassic. These formations consist mainly of sandstone, coal shale and gray to dark-colored limestone. Tectonically, the area is active and there have been several earthquakes in and around this area. The main systems of the faults of the region are thrusts and then strike-slip faults. In sub basins, the hypsometric integral values range from 0.18 to 0.66. Unlike the average height of the sub-basins, which has a natural trend, the hypsometric integral in the region is heterogeneous and has been distributed depressively. The average slope of the sub-basin is 18 degrees and its maximum slope is 33 degrees. The values of SL index range from 72 to 985 m. High values of SL are observed in the center, east and southwest of the region. The core of the high values is located in the center of the region, where major and minor faults are observed.

The purpose of this study was to provide a map of SL index in northern mountain of Damghan. The indicators used in this research, such as slope, hypsometric integral, longitudinal elevation and river gradient, were automatically calculated using GIS and digital elevation models. The results showed that the presence of faults and their uplift were related to the high values ​​of the SL, indicating a different uplift in hole parts of the region. The maximum values ​​of the SL index were observed around the faults, especially in the central part of the studied area. The results also showed that sub-basins with high slopes also had high hypsometric integral values. This can also indicate the high degree of erosion processes. Considering that in this study DEM, topographic maps and interpolation methods were used to calculate the longitudinal gradient of the river, it seems to be more comprehensive than the longitudinal profile of the river, and provides a broad view of the geomorphological processes of basins and sub-basins

On a national scale, soil erosion in Iran, has an important effect on agricultural production, sedimentation in dam reservoirs, soil degradation and so on. Severe soil erosions and the subsequent high deposition of sediments in dam reservoirs and reduced soil fertility are serious environmental problems with dangerous economic consequences for the country. The situation of sedimentation in Iranian dams indicate that their design have often focused on civil engineering and structural aspects and no attention has been paid to the issue of erosion and sediment yield in the basin of dams, which makes a large amount of sediment be deposited in many of these dams for many years; this causes a lot of sediment after many years to be deposited in many of these dams` reservoir, as a result of which, the useful life of the dam is greatly reduced. The present study aimed at estimating soil erosion in the Tang-e-Sorkh dam watershed with a total area of 39,000 hectares in the east and south-east of Boyer Ahmad County in Kohgiluyeh and Boyerahmad province using the RUSLE model and the remote sensing (RS) and Geographic Information System (GIS) capabilities in order to plan protective measures in the dam watershed.

Digital altitude, precipitation, physico-chemical properties of soil and satellite imagery data were used to estimate soil losses using RUSLE model in the Tang-e-Sorkh basin. First, the boundary of Tang-e-Sorkh watershed was drawn on a topographic map with a scale of 1: 50,000 in the geographic information system environment. The meteorological stations in and around the watershed were then identified and marked on the map. RUSLE has calculated the average annual soil erosion expected on a sloping land using Equation (1).A=R.K.L.S.C.P (1)   Where A is calculated as the average spatial loss of soil and the average time of soil loss per unit area is expressed in terms of units selected for K and the time period selected for R. In practice, these units are usually selected so that A is expressed in tons, per hectare, per year (t ha-1 year-1). R Runoff-rain erosivity factor is expressed in MJ mm ha-1 h-1 year-1, K Soil erodibility factor which is the amount of soil loss per unit area of erosion index for a given soil- is obtained by measuring in a standard plot with a length of 22.1 meters, a slope of 9% and a permanent fallow and is expressed in t ha h ha−1 MJ−1 mm−1. L is the slope length, S is the slope, C is the plant cover management factor and P is the protective measures factor. The parameters L, S, C and P are without units. The layer of parameters of the RUSLE model includes rainfall erosivity (R), soil erodibility (K), slope and length of the hill (LS), vegetation management (C), and soil conservation operations (P) have been prepared in geographic information system environment and after overlayering, the amount of erosion was estimated locally.

The amount of rainfall erosivity was from 179.62 to 327.77 MJ mm ha-1 h-1 year-1. Erodibility factor was from 0.08 to 46.0 t ha h ha−1 MJ−1 mm−1. The minimum and maximum values of slope and hill length were 0.08 and 12.42, respectively. The minimum and maximum values of vegetation management were 0.33 and 0.54, respectively. The minimum and maximum values of soil conservation operations were 0.5 and 1, respectively. The amount of soil erosion in the studied area varied between 0.0033 and more than 100 tons per hectare per year at the pixel level. About 80% of the studied area had an erosion rate of 35 tons per hectare per year, with the highest amount in the western and northeastern parts of the country, which was due to high rainfall erosivity and soil erodibility in the area.

It can be said that in the current situation of Tang-e-Sorkh watershed, due to the lack of real sediment statistics, the best model for estimating erosion and sediment yield with the aim of introducing soil protection measures at the basin level was RUSLE model. The proposed method and the results of this research can be used as a dam maintenance planning system. The RUSLE model could predict the potential of soil erosion as a cell-by-cell, which was very useful when trying to identify the spatial pattern of current soil losses within a large area. Spatial information systems can be used to separate and inquiry these locations to assess the role of effective variables in the amount of soil erosion potential observed. Regarding the results, decision makers need to manage the risk of soil erosion in the most effective way; and management scenarios can adopt the best ways to improve and rehabilitate the basin based on the priority of different areas of the basin.

Natural hazards cause enormous damages every year. Among the natural hazards, floods, earthquakes, and droughts have special importance in financial and human losses. Meanwhile, according to the available statistics and information, floods in some parts of the world, especially in Asia and Oceania, have the highest damage. Iran is one of the arid and semi-arid regions of the world with particular climatic conditions. Inappropriate spatiotemporal distribution of rainfall in such regions has caused devastating floods. In this study, flood vulnerable areas are identified by determining the effective parameters of flood using Shannon entropy model. The results of this study can be used in flood zoning and forecasting and planning and management of water resources in the region.

In multi-criteria decision-making problems having and knowing the relative weights of the existing indicators is a significant step in the problem-solving process. (Relations 1 to 6). (1) Aij= (2) (3) (4) Ej=  i=1,2…,m   (5) wj=dj/∑dj  (6) wj= Entropy method is one of the multi-criteria decision-making methods for calculating the weight of criteria. This method requires a criterion-option matrix. The steps of Shannon entropy method consist of five steps of the decision matrix, normalization of the decision matrix, calculation of the entropy of each index, the calculation of deviation, and calculation of weight value Wj. In the Shannon method using the experience and knowledge of experts appropriate factors are determined and weighed. After collecting the questionnaire data and considering the geography of the study area, the scores of each factor are adjusted.

Natural parameters of flood occurrence in Hamadan province include: climate, snowmelt, slope, soil type, Gravilius coefficient, and vegetation. Due to the climatic characteristics of the province, most of the province's rainfall is due to the Mediterranean systems. In winter, the rains are in the form of snow, and in the early spring the melting of snows is accompanied by spring rains which most of the time causes the rivers to overflow. Due to the severe destruction of vegetation in the province, the potential of the region in flooding has been increased. In general, it can be said that the occurrence of floods in any region is due to the confrontation and alignment of human and natural factors. This study only examines the natural causes of flood. The study of the effect of each parameter in the occurrence of floods based on the data-expert method showed that the six factors studied in these studies do not have the same effect on reducing or increasing floods in the basins.

Based on scoring the natural factors that cause floods, according to the intensity of their impact, the flood-prone areas of the province have been identified. Based on the combined data model and Shannon entropy, the highest weighting was given to the maximum 24-hour precipitation. Vegetation factors, snow melting time, basin slope, soil type and Gravilius coefficient were identified as the most effective natural factors in causing floods in Hamadan province, respectively. Based on the final weights, a hazard map was drawn using the GIS. According to the hazard map, the very high risk regions are located in the central and southern parts of the province. Also, the northern areas including the cities of Razan, Kaboudar Ahang and Dargazin are located in high risk area.
 Using the results of this study, it is possible to identify the approximate time of flood occurrence and flood-prone areas in Hamedan province.

Soil erosion has significant environmental impacts and economic losses on crops and reservoir capacity, and affects water quality both directly and indirectly (Issaka and Ashraf, 2017: 3). Therefore, identifying factors affecting soil erosion and ranking the prevention methods in rural areas provide valuable information for managers and planners for soil conservation (Asadi et al., 2016: 99). Soil erosion, on the one hand, is affected by natural features and, on the other hand, by human activities. The type of precipitation regime and water erosion, erosion-sensitive formations, low natural vegetation cover, topographic conditions of natural factors, incorrect use or overuse of lands, poor pasture grazing, plowing of low-yield rainfed fields, and implementation of construction projects, such as road construction, building construction, and mining, without considering the principles of soil protection are the factors caused by human intervention in the country (Darabi et al., 2018: 201). The most appropriate scientific methods can be selected to prevent soil erosion in accordance with the opinion of relevant experts and scientists. Another important issue is the use of appropriate criteria and sub-criteria   to obtain final responses. In fact, if the study method is selected properly, but the criteria and sub-criteria used are not of the desired quality, the results are not reliable and the final output will cause deviations in the final decision. Therefore, it is necessary to extract all required criteria and sub-criteria from the research literature and validate them by experts. Among the methods used to control soil erosion are contour plowing, mulching, mixed cultivation, adding organic fertilizers and manure, grass cultivation, terracing, and cultivation on contour lines (Begum Nasir Ahmad et al., 2020: 104). Darmian County is one of the important agricultural centers of South Khorasan province. As reported previously, 93.3% of the total area is in the severe desertification class (Parvaneh, 2009: 150). According to most studies on multi-criteria decision making techniques (MCDM), the VIKOR technique results in a lower percentage and intensity of changes and yields more valid results (Nazmfar and Padarvandy, 2015: 36; Kim and Ahn, 2019: 126). Therefore, this technique was used in the present study. Keshtkar et al. (2017: 133) conducted a study with the aim of prioritizing the biological management options of Delichay watershed using MCDM. They identified four biological management activities and developed 16 management scenarios in the region. Also, the social, ecological, economic, and physical criteria were assigned the first to fourth priorities, respectively, and scenario number 10 (grazing management and pit-seeding) was determined as the top scenario in the first priority. Vulević et al. (2015: 317) prioritized soil erosion vulnerable areas in the Topčiderska River Watershed, northern Serbia, using multi-criteria analysis methods, and identified the most vulnerable sub-basins due to a significant presence of arable and very steep arable lands, which, therefore, had priority for protection. Also, Zhang et al. (2020: 1331) identified priority areas for soil and water conservation planning using multi-criteria decision analysis in the Xinshui River watershed, China. They selected six assessment indicators, including slope gradient, precipitation, NDVI, land use, soil texture, and slope aspect. They concluded that more attention should be paid to the slope of farmland   and grassland during the planning and management of soil and water conservation projects. Darmian County is an important region in terms of agricultural and horticultural products and severe erosion that threatens the products and natural resources in rural areas. In this research, therefore, an integrated approach based on the multi-criteria decision making methods, including Best-Worst (BWM) and the VIKOR methods, is presented according to expert’s opinions to analyze the factors affecting soil erosion and ranking the prevention methods in the rural region of Darmian, South Khorasan Province.

In this study, the weights of the identified criteria and sub-criteria from the research literature and experts’ opinion were first determined using the BWM and then the VIKOR method was used for ranking the erosion prevention methods. According to the review of the literature, many methods have been proposed to rank the methods of preventing soil erosion. However, these methods usually have a relative level of uncertainty due to a high level of decision maker involvement in the production of final answers. However, the best-worst method has a very strong approach in determining the weight of criteria compared to other decision-making methods (Rezaei, 2016: 126).

This is one of the powerful methods in solving the multi-criteria decision making problems used to obtain the weights of options and criteria (Rezaei, 2016:126). This method compensates for the weaknesses of methods based on pairwise comparisons (e.g., AHP and ANP) such as incompatibility. In addition, it reduces the number of pairwise comparisons significantly by only performing reference comparisons. In recent years, the best-worst method has been used by many researchers to determine the weights and rankings of options in various fields.  

This method is an adaptive ranking technique that is often used in situations with different conflicting criteria (Opricovic, 1998: 5). This method creates a compromise solution based on "proximity to the ideal solution and mutual agreement through concessions". This method has been widely used by many researchers to rank options (Arab Ameri et al., 2018: 1400; Gupta, 2018: 47; Opricovic and Tzeng, 2004: 445). It uses linear normalization that specifies a summation function indicating the distance from the ideal solution. 3- Results and Discussion The criteria and sub-criteria used in this research (based on a review of the research literature) are presented in Table 1. Table (1): The criteria and sub-criteria affecting soil erosion Sub-criteria Criteria Sub-criteria Criteria Aggregate stability Technical Destruction of vegetation Environmental Water penetration capacity Surface water flows Depth of soil Runoff volume Clay particles Chemical Destruction of ecosystems Soil organic carbon content Drought Climatic Non-use of livestock manures Social Fire Rainfall Overgrazing Land slope A consensus method was used to achieve valid results, as for gathering information, a committee of experts was asked to evaluate the performance of the options against the criteria (Table 1) using the scales listed in Table 2.  Table (2): Verbal scale for pairwise comparisons of best-worst methods and Victor techniques Scale for the best- worst approach EquallyImp. Equal to moderately Imp. Moderately Imp. Moderately to strongly Imp. Strongly Imp. Strongly to very strongly Imp. Very strongly Imp. Very strongly to extremely Imp. Extremely Imp. 1 2 3 4 5 6 7 8 9 Scale for Victor technique Verbal expressions  Degree of Imp. for  negative effect criterion Degree of Imp. for positive effect criterion Least Imp. 5 1 Moderately Imp.  4 2 Strongly Imp.   3 3 Very Strongly Imp.  2 4 Extremely Imp. 1 5 P.S. Imp. = Important Calculating the weights of the criteria using the best-worst method Out of all the criteria, the best and worst criteria were selected by experts through mutual agreement. The priority of other criteria was also determined by the worst criteria. After collecting the best-worst method questionnaires, the weights related to the criteria and sub-criteria were obtained using the GAMS optimization software version 24.3 by the BARON solver. The degrees of priority for all the criteria were achieved to calculate the optimized local weights. The results showed that the "technical" and the "chemical" criteria had the highest (0.293) and the lowest (0.085) local weights, respectively, among all the examined criteria. Prioritization of erosion prevention methods using the VIKOR method After achieving the weights of the criteria, the methods of erosion prevention were prioritized in the next step based on the weights of these factors using the VIKOR method. According to the computational results, the technical and the chemical criteria (with scores of 0.293 and 0.085) had the highest and the lowest ranks, respectively. In the final prioritization of the erosion prevention methods, Biochar and injection of organic maters were in the first and second ranks, respectively, and artificial rain was at the lowest rank.

In this research, a new combined approach is presented based on the best-worst method and VIKOR technique to identify the factors affecting soil erosion and to rank the prevention methods based on the opinions of experts and scientists in the field of agricultural development. According to the obtained results, "technical", "climatic", and "environmental" sub-criteria are the three important factors in evaluating erosion prevention methods. In the next step, the options were finally ranked using the VIKOR method, indicating that the top three options are "Biochar", "Arch planting", and "injection of fertilizers and organic matter", respectively. Considering that the development of infrastructure to select scientific methods to prevent soil erosion in rural areas is one of the effective factors in the development of agricultural science in the country, studies in this area should be given more attention. It is expected that the results of this research can provide a suitable tool for managers to make correct decisions.