فصلنامه پژوهش های فرسایش محیطی
سال نهم شماره 1 (پیاپی 33، بهار 1398)

Watershed describes an area of land that contains a common set of streams and rivers, which all drain into a single large body of water. For sustainable management of watersheds, soil erosion is a major factor, which accelerates the rate of land degradation and hence influences agricultural productivity, run off movement and sometimes leads flood in the lower basin. Soil is one of the most important elements of natural resources in each country. In areas where erosion is not controlled, soil gradually erodes and loses fertility. There are two methods to maintain soil and prevent erosion: direct method and indirect method. One of the direct methods to prevent erosion is the construction of checking dam. These structures are constructed in floodplains and perpendicular to the flow of reducing water velocity and run off erosion by reducing the bed slope. Check dams are constructed using materials such as wood, stone, rock, and mortar and gravel (gabion). The aim of the present research is to determine the suitable location of mortar and gabion check dam in Ghorchay Ramiyan watershed based on multi-criteria decision-making methods.

Gorkhay basin (one of the sub basins of Gorgan Rood basin) is located in the southern Gorgan Rood basin and in south of the city of Ramiyan, Golestan province. The hydrometric stations of Ramiyan and Nodeh were used for data analysis that located inside and  in the neighbor of study area respectively. Criteria and indicators are chosen for evaluation of topic. The research criteria were also considered as factors influencing the location of check dam construction site in separate clusters for the second layer. The classes or options are classified in the third layer based on the risk classes in a separate cluster. In a hierarchy analysis, the normalization is performed using Saati method on the comparison matrix. In this research, the vector of the weight of the options is calculated using the geometric mean method. Prioritization was done using the AHP model and GIS based on effective criteria such as physiography, hydrology, geology , soil science and socioeconomic factors.

The weight of socioeconomic, hydrological, physiographic, soil and geological criteria is equal to 0.409, 0.124, 0.0558 and 0.409 respectively, which indicates the impact of criteria on site selecting of gabion and stone-mortar check dam. Based on weights prioritization, priorities 1 to 5 is selected for construction stone-mortar check dam belongs to 14, 10, 13, 6 and 9 sub-basin. Sub-basin No. 14 with a weight of 0.304 is  the first priority and sub-basin No. 1 with weight of 0.129 is the last priority. Among the sub-criteria, the sub- criteria of sensitivity to erosion of geology formation with 0.36 weight has the greatest effect and the sub- criteria of flooding coefficient and slop percent with weight 0.05 have the least effect on the selection of the first priority, that is, sub-basin No. 14. On the basis of prioritization of 62 sub-basins final weights with 2nd grade channel for construction of gobbins, the priorities 1 to 5 belong to the sub-basins 35-35-34-32-57, respectively. Sub-basin No. 36 with a weight of 0.453 as the first priority and sub-basin No. 1 with a weight of 0.113 was proposed as the last priority for construction of gabion.

The rapid growth of technology and economic has transformed human’s life in recent decades and has challenged modern societies with sophisticated decision making. The basic characteristic of such issues is the existence of non-homogeneous and inappropriate criteria or objectives, such as cost, reliability, performance, safety and productivity. Sub-basin No. 14 with weight 0.304 as the first priority (at the end of the basin, which has a slope and high erosion due to formations such as limestone and marn) and sub basin No. 1 is the last priority with weight 0.129 (Shale Formation, Sandstone and coal with high sensitivity to erosion and distance from residential areas and away from resources). Among the sub-criteria, formation erosion sensitivity sub-criteria with weight 0.36 has the greatest effect and the sub-criterion of distance from the road with a weight of 0.01 has the least effect on the selection of the first priority, the sub-basin No. 14. The purpose of this research is to assist managers and decision makers in the Watershed Management Department to select the most appropriate options and to rank the location of structures based on choosing the best decision options and emphasizing on effective decision making by introducing and applying scientific decision-making methods.

A dust storm is one of the biggest serious environmental problems in the arid and semi-arid regions of the world, causing irreparable damages to farms, facilities, roads, traffic and transportation every year and respitory problems by contaminating the air. Due to the geographic location of Iran which is  in the arid and semi-arid belt of the world, the country is frequently exposed to local and synoptic dust systems. Considering the increasing occurrence of dust in the coming years, drought and climate changes and the emergence of desert zones, the study of this phenomenon is considered important and should be studied by using scientific researches to identify the factors affecting the occurrence of this phenomenon and dust source areas. The main purpose of this research is to identify the sources and also track the dust route entering the east of Iran using the HYSPLIT model, satellite images and synoptic analysis.

In this study, At first, warm season dust storms were studied by using weather data, phenomenal code and horizontal visibility. Then, the storm from August 12 to 14, 2018, was recorded using weather data for East stations and horizontal visibility. For more accuracy, MODIS images of the storm wave on this day were identified and the surface dust concentration was confirmed using the AOD Index. Then, using the European Center for Average Meteorological Data (ECMWF) with a spatial resolution of 0.25 * 0.25, sea level pressure (SLP), temperature, direction and wind speed, and geopotential height At 850, 500 and 250 levels, jet streams were investigated and The synoptic factor of the dust storm was determined. In the next step, using the HYSPLIT model, the path of motion of particles and their source were determined at three levels of 500, 1000 and 1500 meters for 24 hours before the storm. The meteorological data of the model was obtained from a 0.5 degreess GDAS.

The intensity and extent of the dust storm from August 12 to 14, 2018 showed that its horizontal visibility had been decreased to less than 200 meters across stations in eastern half areas of Iran. On this day, the dry bed of Hamoun, Pozak, Saberi and Hirmand, Afghanistan's plains have been contributed to nourish the storm. The results of synoptic studies showed that when there is a high pressure independent cell in the north-east of Afghanistan and north-east of Iran as well as a low-pressure cell in the southwestern part of Afghanistan, a severe gradient is made between these regions that causes the wind speed at ground level to be more than 14 meters per second. The severe pressure and temperature differences in the region, the lack of humidity and the high radiation angle have drove the dust of deserts outside the northern and eastern borders toward the region, and this area has been under the Azores subtropical high pressure, which its blockage at high levels leads the persistence of dust for three days in eastern Iran. The results of the model also showed that more than 90% of the dust entry routes to the east enters the eastern part of Iran from the deserts of Turkmenistan, Khazakhistan and Afghanistan.

Due to 120-day winds, low humidity, poor vegetation and dry regional substrates, the eastern part of Iran is prone to the frequent occurrence of dusty phenomena. Based on satellite images and AOD index, the storm has formed in the desert region of Turkmenistan and has been expanding to eastern Iran. According to the synoptic study of the warm period of the dust storm in the east, the upper levels of the Iranian plateau are under the control of the Azores high pressure and on the ground surface, the thermal low is also increasing in the eastern half. When two strong low-pressure nuclei with a 990 hp center in southeastern Afghanistan and southeastern Pakistan were deployed so that its tabs penetrated into the studied region and progressed to the Mediterranean, it created the appropriate conditions for climbing a huge amount of dust into the air that in the case of dryness of the area and north-northwestern and northeastern flow of the upper levels, this phenomenon intensified and moved to the eastern part of Iran. At high atmospheric levels, due to air stability and blocking events, as well as air stagnation, the dust is more durable temporally and the process of bringing it down to the ground surface will last longer days. The results of the HYSPLITE modeling output also showed that the source of dust of the eastern half of Iran in the storm studied enter the studied area from the deserts of Turkmenistan and northwest of Afghanistan and Khazakhistan with the north, northwest and northeastern directions up to 90 percent. In all cases, the results of the model are compared with and confirmed by satellite and synoptic studies.

Aghajari Formation as the last unit of Fars Group cropps out in Hormuzgan Province with a considerable thickness. This Formtion is composed of red sandstones and green to reddish grey silty marls. According to Kalantari (1992), this formation has the age range of Middle Miocene to Pliocene. The thickness of this formation reaches to 3000m in northern Bandar Abbas (Gholamalian, 2012). The great thickness, broad expansion, slothness (with attention to the calcareaus matrix) and presence of some amounts of Iron rich minerals as grains are charactristics of this formation mineralogical composition. Also, these rocks contain polycrystalline quartz, wavy extinction quartz, fossil fragments and some minor minerals such as moscuvite, chlorite, albite, orthoclase in addition to oligiste. In order to identify the origin of the mentioned minerals; several samples are studied by microscope and Some are processed
by chemical analysis. In addition, the origin of oligiste particles in was considered; so, some samples containing this mineral were collected from Hormuz Series of Siahoo, Anguran, Zendan and Hormuz salt diapirs.

The studied area is located in 74 km North of Bandar Abbas, near the Siahoo and Aghasin villages. We should Go 64 km northward from Bandar Abbas and then 10 km eastward in order to access the studied section. The studied section is approximately 4 km before the Aghasin village. Fifty samples were collected from Aghajari Formation and Hormuz Series for
 the sake of this study; 22 of them were for chemical analysis and 20 for microscopic thin and polished sections. Three oligiste samples are collected from salt domes for comparison to the Iron rich mineral grains of Aghajari Formation. Oxidic and elemental XRF analysis of samples performed on 22 samples. In addition, point analysis of microprobe exercises are done on the rock forming grains of Aghajari Formation and Hormuz salt plug oligisites with XRF method. Thin and polished sections are studied by polarizan and reflective micoscopes.

Microscopic investigations on the thin sections of Aghajari Formation Showed the mineralogical content of rocks. Average mineralogical component of grains in this sandstones includs %45 to %50 quartz (%20 wavy extinction quartz and %25 to %30 polycrystalline quartz), less than %10 albite and orthoclase, %3 to %5 black oligiste and %30 to %35 calcareous matrix.
Quartz is the main mineral in the grains. Polycrystalline and wavy extinction quartzes can generally form in metamorphic phases. On the other hand, angular to semi-rounded quartz Grains show short distance transportation. It seems these quartz grains are originated from the Sanandaj – Sirjan metamorphic belt rocks. Weak mineralogy and grain size sorting and high thickness of Aghajari Formation show fast sedimentation and short distance transportation of grains. On the other hand, comparison of microprobe spot XRF analysis of oligiste grains shows the chemical composition similarity of this mineral in Hormuz series and Aghajari Fomation sandstones. So, these mineral grains are transported from Hormuz series salt plugs to the sedimentary environment during deposition of Aghajari Fomation in the Late Miocene to the Pliocene.

Results of XRF analysis, microprobe and microscopic investigations prove the presence of Fe2O3 as oligiste grains in the Aghajari Formation sandstones. Results of point analysis of these particles are similar to those of Hormuz series; showing the probable origin of oligiste particles in the sandstones. A large amount of quartz is present in the Aghajari Formaion sandstones that cannot be transported from salt plugs, because there are a few amounts of this mineral in the Hormuz Series.
Wavy extinction quartz grains are abundant in the Aghajari Formation sandstones and have been originated from Sanandaj - Sirjan metamorphic belt.
Presence of some mineral particles such as: albite, moscuvite, and chlorite in the Aghajari sandstones prove short distance transportation, probably from the Sanandaj - Sirjan metamorphic belt.
In fact, Aghajari sandstone particles are synchronously transported from two main sources; Sanandaj - Sirjan metamorphic rocks are the origin of quartz grains and oligiste fragments are originated from the Zagros Range salt domes.

Different natural phenomena have many variables that make it difficult to find relations among them using common mathematical methods. This problem, along with the impossibility of measuring all elements of nature, has led to a major evolution in the procedure of scrutinizing and explaining. In this way, we can use the fractal geometry with the theory that the order of many natural phenomena is chaotic. Fractal geometry is a quantitative tool for studying the geomorphology of drainage networks and modeling many complex natural phenomena. In fact, geophysical phenomena such as basins are fractal phenomena with fractal behavior. An understanding of geomorphologic characteristics and their performance over basins is very important in the watershed management. This paper focuses on the relationship between fractal dimensions of basin shape and drainage network with the geomorphologic characteristics of basin. Therefore, through an analysis of fractal dimensions and its comparison with geomorphologic characteristics, the fractal behavior of this basin is investigated.

The present study consists of four main sections. The first section is the collection of maps and data. In this section, topographic maps at scale of 1:50000 and geological map at scale of 1:100000 from area were provided. Then, the required layers were extracted from them such as drainage networks and geological units. Sensitivity to erosion of formations was studied in this basin using PSIAC method. In order to investigate more precisely, the Aqda was divided into nine hydrological sub-basins (independent), five non-hydrological sub-basins (dependent) and four hybrid sub-basins. The second section, 18 geomorphologic characteristics were calculated for each sub-basin. In the third section of this study, fractal dimension of drainage networks and basin shape was calculated by box counting method using Fractalyse software in each sub-basin. The focus of the final section is on the relationship between fractal dimensions of basin shape and drainage network with the geomorphologic characteristics of basin.

The results showed that the T8 and To3 sub-basins, respectively, with values of 1.47 and 1.60 have the highest fractal dimensions of the drainage network. Also, the highest fractal dimensions of the basin shape were obtained with values of 1.05 and 1.08, respectively, in the same sub-basins (T8 and To3). The results also indicated that there were significant relations among the fractal dimensions of the basin shape and the drainage network with geomorphologic characteristics. The highest correlation belongs to the regression relations between the total length of stream, basin area and erodible area with the fractal dimension of the drainage network (0.98, 0.97 and 0.95 respectively). Fractal dimension of the basin shape showed the highest correlation of 0.82 and 0.8 respectively with the number of networks and the total length of stream (significant at 99 percent level). Then, the erodible status in Aqda Basin was determined by studying the geomorphologic characteristics and comparing it with the fractal dimensions of the basin shape and the drainage network. The highest erodible status is in T8, T1, T6 and TO3 sub-basins which should be considered in strategies to manage Aqda basin. In fact, this study showed that fractal dimensions allow a quick and accurate analysis of the geomorphologic characteristics of the basin and the drainage network.

Identification, evaluation and prioritization of different areas can produce valuable information for the watershed comprehensive plans, soil conservation and mitigation of the erosion types based on amount of erosion and sedimentation. For this purpose, the geomorphologic characteristics should be investigated in basins. But extraction of these characteristics and estimation of the erodible status in basins are time-consuming and costly. Therefore, it is very necessary to use an index that has an appropriate estimation of the erodible status in basins. Fractal dimension, with time and cost management, can determine sensitive and high priority basins. With knowledge about the relationship between geomorphologic characteristics basins with fractal dimension, we can predict the other characteristics of basin. The results of this study indicated that there were significant relation between the geomorphic characteristics of sub-basins study and fractal dimension of the basin shape and the drainage network. Other researches on fractal dimension analysis have shown that there is a significant relation between fractal dimension and characteristics such as basin shape, area, branching ratio, drainage density and length ratio of drainage network. But in this study, two characteristics of branching ratio and length ratio of drainage network were not significantly correlated with any of the characteristics and fractal dimensions, and the drainage density was correlated only with frequency rank. Therefore, basins with high erosion will not always have high drainage density. For example, quaternary alluvial deposits have high erosion, but their drainage density is not very high (T4 sub-basin). For this reason, in the future studies, it is better to separate the tectonic streams from the erosion streams. Finally, the results of this study can confirm the findings of other researchers that fractal dimension of drainage network reflects the complexity of the basin shape and can be used as a quantitative index for basin analysis and evolution of the basin.

     The purpose of this research was evaluating the effect of the 120 -day's winds on flood flow entering deposit to Sistan region. At first, it became clear that flood flow path to Sistan area after the floods and droughts, according to the file work is randomly sampled from the flood deposits accumulated for a period of 3 years. Also, high deposit was measured with filed work in two periods before and after the begining of 120-days winds. In order to study the graded sediment samples and granulometry, the parameters were determined middle (D50), Mid-average, Kurtosis, Skewness and sorting. For analyzing the winds of the region WRplot view 8 and the harvest sand rose Software were used. In statistics study parameters of graded flood flow deposit entering to Sistan shows that the average particle size of sediment is 88 microns and mainly were fine-grained sediment. By determining the threshold of peak flow deposits, the frequency of prevailing winds and also draw sand rose of stations points of study, data shows that the high cumulative flow of sediment erosion affected by winds of 120 days of Sistan region. As the frequency of winds over speed ​​threshold is 100 percentages to study station. In study of sediments height, the results showed significant differences at 0.01 levels (p < 0.01) between the heights average of sediment before and after the beginning of 120 days winds in Sistan region. Therefore, according to analyzing Granulometry of Sediments transported by floods, determined threshold and the capability of carrying particles by local winds as well as field measurements, these deposits are the main resources harvested with starting 120- days winds along with flood flows intering Sistan region each year, eroding and causing a lot of problems in that region.
 

In this research we have provided data about the direction of rivers in Afghanistan country watershed. We used accessible images of Google Earth for determining peak flow path in the Sistan area and according to the luck ontinuity of flow in the region, areas that have been affected by flood flow was determined. In the following, it was found rods of Sistan region.  After the floods and droughts, during field operations, accumulated flood sediments samples were collected randomly. Also, the sediment level in scale (Sediments transported by floods and depth of drilled by wind sediments carried by wind) of the 14 points were measured. The above steps have been done during each incoming flow to the Sistan region during 3 years (2016-2018). To evaluate the constituent particles of sediment in granulometry, 60 samples were selected and analyzed in Sistan Agricultural, Natural Resources Research and Education Center lab. In the study of granulometry of sediments taken with respect to deposits collected by 20 sieves. The estimation depth of accumulated flood sediments for two stages before and after the 120-day winds flood in summer. Selected by accumulated flood sediments and high measured sediments. In order to study the graded sediment samples and granulometry, parameters were determined middle (D50), Mid-average, Kurtosis, Skewness and sorting. For winds of region analysis, we used WRplot view 8 and the harvest sand rose Software. In statistics study parameters of graded flood flow deposit entering to Sistan shows that the average particle size of sediment is 88 microns and mainly were fine-grained sediment.

By determining the sediment in granulometry, frequency curve of particle was drowning for each of the study samples. Drawing on sediment size distribution for each sample, the results of the study analysis parameters, were estimated the peak flow of sediment into the Sistan region. Based on the results, the median and mean values ​​of accumulated sediment on the bed river (Sistan River) and Hamon wetland were phi 6.2 and 6.4, respectively. Changes in these parameters are almost identical, but in some areas, the median value is greater than the average value which is due to finer grain particles. The general trend changes two parameters; the mean and median separable in study terms. In the first year, medians index was more than the average value of the samples taken which indicates that the presence of fine particles is more than coarse particles percent (the average size of silt). Whereas in the second year, the average of sediment samples taken increased the size of the fine silt particles coarser grain and reduced the fine silt particles in much finer grain. In the third year, the mean and median values ​​are almost identical and fine silt was deposited as sediment size. The result shows that the tilting parameter values of sediment samples of peak flow was from very good tilting (0.22) until very weak tilting (2.86). Study of parameter values ​​tilting this parameter indicates the rate of change between 0.14-0.76.

In this study, for the first time has survey graded sediment input peak flow in Sistan. Then determine particle size and analyze the wind of the region, was estimated attrition of the sediments. In examining sediment samples in granulometry, during study period and the overall changes under the influence of mean and median and existence fine and coarse particles was perceptible in the overall trend analysis of these two parameters. Fluctuations in hydrological and hydraulic conditions prevailing in the bed of peak flow to Sistan area includes Sistan and Frahe rivers are determining particle transport in flood deposits. In support of this important Morphometry properties including sorting that reflects that the energy levels in sedimentary environments and energy situation is stable over time shows that the natural sediment sorting peak flow is not formed under the influence of hydraulic and dynamic conditions governing the flow of the river. In the other hand, because the rivers are seasonal and alluvial transmitter rivers transfer flood flows in the Sistan region, decrease the sediments have been sorted turbulent flow conditions along the river and rapid changes in river flow and erosion phenomenon over time. The results showed that sediment in granulometry of sediments transported during peak flow is always fine which has a low threshold velocity and due to the frequency and intensity of wind in the region, this has eroded sediments which effects of like phenomena dust and endangering the health of residents. Therefore, according to the analysis in granulometry of sediments transported by the floods and determined threshold, capability of carrying particles by local winds and field measurement, these deposits are the main sources of harvest starting with 120 days winds.

There was about 15 percent of the world's soil erosion at the beginning of the twenty-first century that nearly 11 million square kilometers was affected by water erosion. Soil erosion after population growth is a serious threat to the environment, health and well-being of humans, and it has been introduced as the second most important environmental challenge in the world. The annual level of soil erosion in the world is 75 billion tons and Iran's share is more than 2 billion tons and about 3 times more than the total soil erosion which has been reported in Asia. On the other hand, the amount of soil erosion in north of Iran is 15 to 25 million tons per year, While the amount of forest per capita is 2.0 hectares in Iran and 8.0 hectares in the world. Soil erosion in the region of Asia, Africa and South America is 30-40 tons per hectare annually, in the United States and Europe is 13-17 tons per hectare and in Iran is 30-35 tons per hectare. The mean erosion in Iran is about 3.4 times the average erosion in the world. In the present study, we used Fournier and Douglas models to predict the amount of sediment in the watershed of Karaj.

Karaj river Basin (to the Amir-Kabir dam) with an area of 764 square kilometers, is located in north latitudes between 36 degrees and 10 minutes and 35 degrees and 57 minutes and East longitude between 51 degrees and 3 minutes and 51 degrees and 35 minutes east. The highest elevation in the basin which was studied is 4343 meters and the lowest elevation in the Karaj dam is 1680 meters. The length of the studied basin is 38/31 km. In the present study in order to estimate the amount of sediment erosion in basin, initially basin has been limited using topographic maps and Google earth. Then the required data was extracted from meteorological and precipitation stations, geological maps and field observations in the study area. Finally, it was analyzed in four models; Fournier, Fargas, Ciccacci and CSY. The first model of sedimentation that put in much effort to extend and improve its results is Fournier model that was presented by him in 1960. Fournier used his model to factor in seasonal precipitation index, which has a high correlation with the yields of deposits. In 1968, Douglas worked on ten factors involved in erosion. And by distinction of top four factors, he presented a formula that is perhaps the most used. Modeling processes of erosion and sediment production, transport and deposition, have been studied before. Sediment transport formula of Bijker (1976 and 1971), one of the first formulas extended to combine current and the wave. Van Rijn in 1984, proposed a comprehensive theory for sediment transportation rates in rivers in basic physic theories and practical observations. Watanabe in 1992, proposed a formula for final deposition based on the capacity of force model. This formula has been widely used for prediction in Japan. In Iran it is also published in the final report of calibration of models by the Soil and Water Research Institute, Watershed management and thesis of graduate students. Behzadfar et al. (2009) studied the erosion index in North Khorasan Province. Pour-Abdullah (1385) used two models 2000SWAT and RUSLE for modeling and comparing the results with the actual values in the watershed Emameh. Salajegheh et al. (1388), Asadi et al. (1389) and Ahmadi et al. (1393) are other domestic papers which have been done about soil erosion and sedimentation. The purpose of this study was to estimate the sediment yield of Karaj basin using morphometric and experimental methods and erosion risk analysis at large catchment areas such as Karaj basin. Which has a strategic and vital importance for supplying drinking water to the capital and metropolitan Tehran-Karaj.

Calculation of Ciccacci et al. 1986 method, which is based on the morphometry of the catchment area, shows that the annual precipitation rate of Karaj basin is 706241.2 tons per year from the basin. According to the calculations, the annual sedimentation rate of Karaj Basin, based on the csy method, is 317648.2 tons from the basin. According to the Fournier model, eroding and sedimentation rates in the whole Karaj basin are 387630.8 tons from the basin. The Sediment-rating Curve Data showed that the annual sediment rate was calculated to be 565605.4 tons per year. In order to evaluate and estimate the risk of erosion in the basin, Fargas method was used. According to the calculations, 29.6% of the area of Karaj basin is in severe erosion. The expansion of the kahar Formation, Ziarat, Asara and Quaternary Formations, and the intense activity of Masha faults and Karaj fault have caused erosion in the Karaj basin. As a result of this increase, this process has reduced the reservoir capacity of Karaj during many years. The moisture and glacial regime in Karaj watershed has always caused the activity of erosion processes such as cerioclasti, thermoclasty and mass movements in different shapes, The erosion rate has increased tremendously.

The results showed that the annual precipitation rate of Karaj basin is 6.91 tons in morphometric method and 4.73 and 3.87 tons per hectare in experimental, forenier and hydrophysical methods respectively. Meanwhile, based on real data of Sediment-rating Curve Data of the regional water organization, the annual sedimentation rate is 6.89 tons per hectare. Therefore, the morphometric method has the closest estimate to actual data and is a suitable method for estimating erosion of sediment in large catchment areas. The difference of quantitate value between the original value and two equations, represents the disqualification of two methods in this study for basins like Karaj River Basin. It seems that other experimental models such as Hydrophisic and artificial neural network models with having alittle difference compared to the real value have the more richness to estimate the sediment load. However, this amount of power of erosion represents a high rate of attrition in upstream river- top of Amir Kabir Dam- and accumulation of eroded sediment mass in the dam.