فصلنامه پژوهش های فرسایش محیطی
سال دوازدهم شماره 4 (پیاپی 48، زمستان 1401)

      Flood is defined as an unconventional increase in river discharge. Complete protection from flood hazards is rather impossible. For those living next to floods, implementing new policies is necessary regarding land use management and development of residential areas along rivers to reduce the effects of destruction. One of the basic steps to reduce the harmful effects of floods is to identify flood-prone areas and grade these at risk. For this purpose, one of the solutions against floods is to prepare for a zone. By using zoning maps in watersheds, flood preparedness can be created. The purpose of this study is to perform the zoning of flood-prone areas in Talar drainage watershed and to calculate the damage in areas eroded and destroyed by floods in 20 meters of river, which due to the geographical location and weather conditions in recent years, this region has been faced with various floods and in this regard, the importance of risk zoning and management and planning of the region intensifies.

In order to conduct this research, input data including digital geological file, digital vegetation file, digital soil file, digital elevation model (DEM) with a spatial resolution of 10 meters, satellite image, and flood event statistics and information were used on 19 July 2015. HEC-1 model in WMS  was used to estimate the hydrograph of SCS unit in Talar basin and Kasilian sub-basin.To determine the flow and boundary conditions, the peak flow number for the flood of 19 July 2015 is 163 cubic meters per second. In order to zone the flood, software WMS and HEC-RAS models have been used.  Since the upstream and downstream slope of the river have a significant impact on the flooding process, the upstream slope is 0.02, and the downstream slope is 0.01. Water elevation points were imported from HEC-RAS program in WMS, and cross section profile plots were prepared at the location of sections located in rural and urban areas, and finally, water depth maps were prepared and compared for the event on 19 July 2015. The Kruger Method was used to determine the maximum instantaneous discharge for 50-year and 100-year return periods. In order to calculate the damage in flooded and eroded areas, a 20-meter area of the river has been considered. Then, the monetary values in each square meter of the covered uses have been estimated according to experts, and finally, the flood damage has been calculated. Duncan-Tukey and ANOVA tests were used to assess the hazard.

    In the SCS unit hydrograph, the peak time is 390 minutes for the Kasilian basin and 555 minutes for the Talar basin. The height of the current water level and the height of the water level at the critical level in some cross-sectional profile plots have coincided, which indicates the dangerous situation in these areas. The largest area of ​​flood zones in the flood of 19 July 2015  in Shirgah, Zirab, and Pol Sefid cities at a depth of  0.6  meters, Do Ab villages at a depth of  0.3  meters, Lerd and Rudbar villages at a depth of  1.2 meters, Darzikola, Vazmela and Sangdeh villages at a depth of  0.6  meters. The highest area of ​​flood zones in the 50-year return period is in Pol Sefid and Shirgah cities at a depth of  0.3  meters with an area of ​​181 hectares, and the 100-year return period in Shirgah with an area of ​​292 hectares at a depth of  0.3  meters. Also, the largest area of flood zones in the 50-year and 100-year return period in rural areas is located in the villages of Valik Ben Sang Deh, Darzikola, and Vazmela, with an area of 276.9 and 188.6, respectively, at a depth of  0.3  meters. The results of statistical tests in the risk assessment section showed that in total, two uses of rangelands with an average water depth of   0.57 meters have the lowest average water depth and urban residential areas with an average water depth of  0.84 meters have the highest average water depth.

According to the flood zoning on 19 July 2015, it was determined that the highest areas of water depth zones of  0.3 meters,  0.6 meters,  0.9 meters,  1.2 meters, and  1.5  meters are located in Pol Sefid city. The zoning of the 50-year and 100-year flood return period also indicates an increase in the area of ​​water depths of 0.3 meters,  0.6 meters, 0.9  meters, 1.2 meters, and  1.5 meters compared to the flood of 19 July 2015. Considering the area of ​​flood depth zones in the flood of 19 July 2015 and the area of ​​land uses covered by flood risk, it was determined that the most damage is related to the Zirab city in residential use with a damage of  266,482,744,183 Rials. Then the city of Pol Sefid with agricultural use with damage of 96,979,434,983 Rials and the city of Shirgah with garden land use with damage of 78,544,366,182 Rials. Finally, flood risk assessment with Duncan, Tukey, and ANOVA tests showed that residential land use has the highest average depth of  0.84 m, and Lerd rural area with an average depth of  1 m has the highest flood potential.

 The water flow that is higher than the river level and penetrates the surrounding lowlands is called flood. In urban environments, due to high human density and its economic importance, the occurrence of floods is important and can lead to a lot of human and financial losses. In the metropolis of Karaj, in the floods that occurred in 2018, in addition to the damage to urban infrastructure, 8 individuals were dead, 10 injured and 12 missing and this phenomenon damaged 40 vehicles as well. Karaj metropolis from a geomorphological point of view, according to the physical characteristics and form of waterways, is characterized by hydrological coefficients of sub-basins, high rock outcrop, and high intensity of storms. Due to the importance of preserving lands and gardens along rivers, and its agricultural status and existence of gardens within its basins, and most importantly, the establishment of Karaj metropolis at the river outlet from the mountains, conducting flood estimation and management and water storage in this basin is necessary.
Therefore, due to the importance of floods in urban issues, a lot of research has been done based on data from 1: 50000 topographic maps and 1: 100000 geological maps, lithology, digital land model, land use, aerial photographs, satellite images and Google Earth in order to obtain flood-prone areas. Therefore, in this study, the hydro-geomorphological features of Karaj metropolitan basins with emphasis on flooding are investigated by estimating and studying the physiographic characteristics of watersheds leading to Karaj metropolis and calculating the probability of floods in different time periods and spatial analysis. In order to manage possible floods, appropriate scenarios and locations should be identified according to the landform characteristics of the basin for storing and maintaining excessive water and floods.

In this research, the research steps are as follows:Required data collection:
Preparation of remote sensing data including: Digital terrestrial model data (altitude, slope and waterway data),
Landsat 8 OLI sensors (land cover data, vegetation density index and FCD index),
Ground data preparation including: Karaj Municipality data (absorption wells, drainage canals and urban lands),
Geological Survey (fault and lithology) data,
Regional water organization data (hydrometry and groundwater),
Meteorological organization data (climate data),
Data from ground observations

 The upstream basins of Karaj metropolis consist of 5 sub-basins named Klak and Hesar (in the east of Karaj metropolis), Azimiyeh, Taleghani, Siah Kalan and Delmbar (in the north of Karaj metropolis). The flow of surface water in the Klak and Hesar basins, which is directed to the Karaj River, and due to the construction of the Karaj Dam upstream of this river, practically possible floods in this basin are directed out of the urban environment by using the mentioned river. Therefore, there are no flood hazards in this basin. However, the northern basins of the city, due to the diversion of all surface water into the urban environment of Karaj metropolis, and the location of this city in its waterway bed, such as Taleghani Street, has faced high flood risks. Therefore, the northern basins of the city have been studied in detail. In Azimiyeh, Delmbar and Taleghani basins, protection measures including diversion canals and water storage ponds have been constructed to control floods, but due to lack of protection and proper management, they have lost their function.
Drainage networks located in the city of Karaj are transferred using two canals and a metro collector, which are located in the bed of the old streams of Kamalabad (Beheshti canal) and Hosseinabad (metro collector). These two old streams have irrigated the lands of Kamalabad and Hosseinabad using the water of Karaj River, so the slope of these canals is from east to west, which collects surface water from the city and through Haftjoye leads to the Shore River.
 The results of flood simulation in different return periods using HecRAS model show that in a 20-year return period, 0.27 cubic meters per second flood is produced in the largest waterway located in Azima, which affects 14 hectares of surrounding land. Also in Taleghani, Siah Kalan and Delmbar waterways, 0.3, 0.58 and 1.91 cubic meters per second of floods are produced, respectively, which affect the area equivalent to 15.82, 22.65, 85.51 hectares of the surrounding lands, respectively. In addition, by using the TOPSIS model and hierarchical weighting systems, the areas with flooding potential were identified. For this purpose, 9 criteria were used and normalized using fuzzy logic model and straight and inverse linear functions, and then using the AHP model, the effective weight of each of them was obtained. The results of zoning show that 56.8% of the area of ​​Karaj metropolis and its upstream basins are exposed to flooding and the potential for flood production, to the extent that north of Karaj and the slopes overlooking the city of Karaj due to he highest slope, height, rainfall and poor in terms of vegetation, are categorized with high and very high flood potential. On the other hand, the southern part of the city, due to the slight slope and rainfall compared to the northern part and the slopes overlooking the city of Karaj, and the density of gardens and vegetation and agricultural lands, has the lowest risk of flooding potential.
With the aim of flood management and by using 14 criteria and a combination of weight assessment (WASPAS) locations to store flood water were identified:  4 locations (end of North Taleghani Boulevard with water storage volume of 4620 meters3, northern part of Azimiyeh slope with 8400 meters3 of water storage, northern part of the Atomic energy street with a storage volume of 8400 cubic meters of water and the northern part of the Epsino Valley with a storage volume of 3000 meters3 of water. Assuming a depth of 2 meters in each of the proposed zones, a total of 20 thousand cubic meters of flood water is self-sufficient through which flood water can be managed. Location of deep and semi-deep well drilling site is another way of managing surface runoff and flood that was located using 10 criteria and MCE model and the result is the identification of 16 sites for construction and drilling of absorption wells. Another measure for surface runoff and flood management is to increase vegetation density. The result of examining the relationship between surface runoff and vegetation density percentage obtained from the FCD distance sensing algorithm, shows that zones with maximum runoff have lower vegetation density. 25% of the area has the most runoff, So, according to the cooficit correlation (%98) between runoff and vegetation density, increasing the area of ​​green space and vegetation density from 25% to 75% reduces the runoff to less than 25 mm which prevents the area from causing floods.

The results show that despite the construction of transmission canals and absorption wells in the city of Karaj, in some northern streets such as Tarbiat Moallem Boulevard, Bouali Gharbi and Nawab Safavi Street located in District 8 of the municipality, as well as Goodarzi and Nedaye Shomali streets in the south, no measures have been taken to control the flood, and due to the impermeability level, heavy rainfall compared to the southern part of Karaj and a steep slope (more than 15%), there are conditions to increase runoff on the street. Also, despite the construction of Taleghani, Moazen and Delmbar canals, which direct the surface water from the Taleghani, Siah Kalan and Delmbar sub-basins to the Beheshti collector, due to the lack of transmission capacity of the artificial canals implanted in at the metropolitan area, excessive surface water enters urban streets and generates floods. In order to manage floods and surface runoff in the city of Karaj, the identification of suitable locations for digging absorption wells and water storage pools has been considred, according to which 16 suitable locations for drilling wells and 4 suitable locations for constructing artificial pools had been identified for storing a total of 36,800 cubic meters of water. Also, increasing the surface infrastructure and vegetation from 25% of its density to 75% will reduce the amount of surface runoff by 75%, which leads to flood management.

The history of life on Earth suggests that humans have always been exposed to a variety of natural disasters (Mayahi, 2021). Some of these disasters are related to climatic factors and fluctuations such as droughts and some are related to human factors (Obiahu, 2020). Land use change and land cover are among the most important environmental issues that have caused global concern (Ota, 2018). Such changes are usually caused by human activities such as deforestation, urbanization, agricultural intensification, overgrazing, and subsequent land degradation. In addition  to, natural factors can also lead to these changes. Factors such as intensive agriculture and overgrazing are major causes of land degradation in arid areas. Changes due to human intervention can lead to the destruction of natural resources. Currently, land use changes from natural lands such as forests and savannas to other uses such as agricultural lands, pastures and settlements have intensified (Chen, 2014.(

2.1 Data used The satellite data used in the present study include two satellite images of Landsat 5TM sensors dated 06/17/2010 and Landsat 8, OLI sensors dated 10/06/2019 with row and transit numbers 159 and 41-42. The digital elevation model (DEM) of ASTER sensor with a resolution of 30 square meters was also used. Satellite imagery and digital elevation models were obtained from the archives of the USGS Web site. 1: 25000 topographic maps from Iran Mapping Organization were used as well. Furthermore, layer construction and composition were performed using ERDAS IMAGINE 2014, ENVI and ArcGIS software.
2-2 Preprocessing of satellite images
In order to control the satellite image in terms of accurate ground recording, geometric correction was performed on the image. To achieve this, images from TM sensors and the OLI sensors were referenced. Because changes in lighting conditions affect the actual radiation reaching to a pixel, atmospheric correction must be made on the images. In the present study, in order to perform atmospheric correction, ATCORE plugin in ERDAS IMAGINE 2014 software and metadata file along with satellite images were used (Iranmehr, 2014).
2-3 Processing satellite images and preparing land cover maps
In order to select educational samples in order to perform supervised classification, aerial photographs, Google Earth images and GPS captured points were used in field operations. The distribution of educational samples in the study area was homogeneous and with proper distribution to the extent possible. The number of pixels selected in each training sample should be at least ten times the number of spectral bands used in the image (Sharma, 2011), which was observed in the present study. The appropriate band composition for classification was determined from the Evaluate command in the Signature Editor based on the Best Average Separability. Based on this, a band composition was used to classify the TM sensor image and a band composition of 2357 for the OLI sensor image.
2-4 Assessing the accuracy of land cover maps
In the present study, after classifying the satellite images, the accuracy of the classified image was evaluated using educational samples that were not involved in the classification process. For this purpose, the classification accuracy was evaluated by using the error matrix and calculating the overall accuracy coefficients and Kappa coefficient.
In order to determine the effect of land use change on soil erosion, the amount of erosion per year in each land use was obtained and compared with each other.

3.1 Classification accuracy assessment
In the present study, the accuracy of image classification was performed by using educational samples and the error matrix and calculating the statistical indicators of overall accuracy and kappa coefficient (Table 4). Using the obtained results, the overall accuracy and kappa coefficient in 2010 are 0.92 and 0.90, respectively, and for 2019 are 0.93 and 0.91, respectively.
3-2 Land use assessment
Examination of the results of land use changes in Figures 3 and 4 as well as Table 5 shows that the land use of the region has changed significantly to the extent that in this 9-year period agricultural land has increased by 54.5 percent from 4.24 percent. The percentage in 2010 has reached 9.78 percent in 2019. Bare and saline lands and residential areas also increased by 3.27 and 0.23 percent, respectively, while forests, pastures and aquifers decreased by 0.01, 7.34 and 1.61 percent, respectively.

Soil erosion is one of the environmental problems that is a threat to natural resources, agriculture and the environment and it is considered one of the main land degradation processes in different parts of the world, including Iran (Patil, 2013 & Brath, 2002). According to the results of  Miahi et al. (2021), basins that have heavy rainfall and showers with a direct impact on rain erosion index will increase the potential for soil erosion (Mohammadi, 2018 & Mayahi, 2021). The results showed that, the erosion class showed a very high increase of nearly 5%. Also, these changes in erosion in the use of pastures and bare and saline lands have been more evident because, in this period, rangelands have decreased and bare and saline lands have increased. According to the findings, the decrease in vegetation due to vegetation degradation, especially in arid and semi-arid areas, will
increase soil loss because vegetation as a protective factor of soil against direct rainfall reduces the erosive force of rain and loss (Obiahu, 2020). Therefore, with the loss of vegetation and land use changes, the possibility of direct rainfall colliding with the soil surface provides the soil to be harvested by water and transported in the direction of the slope. Consequently, soil losses become significant (Descheemaeker, 2008). A similar study by Ota et al. (2018) showed that changes in slope cause differences in chemical and physical properties of soil that lead to changes in soil nutrients and, thus, increase soil loss (Ota, 2018).

Interaction between tectonic and surface processes to create and dissect topography is the main area of emphasis in tectonic geomorphology (Burbank & Anderson, 2001: 2). Growing usage of GIS and DEMs have improved techniques of landscape analysis in Tectonic geomorphology. One of the widely used approaches in tectonic geomorphology to recognize general elements on landscape related to tectonic is analyzing topographic patterns by swath profiles (Perez Pena et al, 2017: 136). To avoid arbitrariness of selecting a single profile line, earth scientists use topographic swath profiles (Telbisz et all, 2013: 485). Examining elevation values associated with corresponding coordinates is one of the most common variables to study by swath profiles (Telbisz et all, 2013: 487، Yousefi Bavil & Yousefi Bavil, 2019: 281). In these projected profiles, contours and equally spaced profile lines intersections are determined inside a band (Grohman, 2004: 1059). In the present study, in order to evaluate the long-term equilibrium of northwestern Zagros landscapes in response to internal and external forces that uplift or tear down its topography, Perez-Pena et al (2017) method of extracting swath profiles has been used. We have also used their new transverse hypsometry index for analyzing hypsometry along the swath. Since different parts of the Zagros are subjected to different tectonic force vectors, thereby, the rate of tectonic processes and the resultant forms are not the same. On the other hand, surface processes make these landscapes’ evolution more complex. To simplify the topographic pattern of these complex processes, 10 swath profiles parallel and perpendicular to the Lorestan arc and its adjacent crushed zone trend have been plotted and interpreted.

Topographic swath profiles are created by projecting topographic profiles with equal space inside a strip or swath (Perez-Pena et all, 2017; Fielding et al., 1994). This method is applied for sampling and analyzing a value and its changes for representing three-dimensional datasets on a two-dimensional diagram that is more systematic than ordinary profiles with arbitrary cross-profiles (Yousefi Bavil & Yousefi Bavil , 2019; Telbisz, et all. 2013; Hergarten, et al, 2014).In the swath profile, statistical parameters of elevation values (maximum, minimum, mean, quartile 1 and 3 as well as local relief) can be calculated and plotted against the distance (Telbisz et all, 2013: 485). Different methods of constructing swath profiles have been explained by Telbisz et al, 2013; Hergarten et al, 2014, Perez Pena et al, 2017, Yousefi Bavil and Yousefi Bavil, 2019. In this article, Perez Pena et al (2017) approach has been used to extract swath profiles which allows constructing swath profiles for curved features. This kind of swath profile is made up of calculating parallel lines to the baseline and sampling their length with defined step sizes. In addition, considering the deviations of mean elevation to the maximum or minimum elevations, by re-scaling hypsometric integral values in a defined range (between 0.2 and 0.8), an enhanced transverse hypsometry index (or THi*) can provide better comparison of hypsometry along swath profile. All these commands can be implemented in GIS software by swath profiler add-in programmed by Perez-Pena et al (2017). Here digital elevation model is the elevation source and a line or curved feature is the baseline. The step size and total width of profiles also can be changed in the input box of the add-in. In this study, swath profiles with 40 meters step size inside a strip with a width of 20 km (10 meters from each side of baseline or main profile line) for five transects perpendicular to Zagros trend (NE-SW) named P1 to P5 and five transects parallel to its trend (NW-SE) named H1 to H5 (fig. 8) along with their main fault have been extracted (fig. 9 & 10). The NW-SE baselines follow the main Zagros faults (Berberian, 1995) in area (Zagros main reverse fault and Zagros recent fault, high Zagros fault, Zagros mountain front fault, and Zagros foredeep fault). Five NW-SE curve lines cross morphotectonic units of Zagros (Berberian, 1995) which are adjacent (High  Zagros thrust belt, Zagros simply folded belt, and Zagros foredeep contains Dezful and Kirkuk embayments).

In plotted swath profiles, mean elevation represents general topographic trend of landscape within swath; minimum and maximum elevation show landscape variation perpendicular to the swath, local relief, and quartile describe topographic variation along the swath. Upward deflection of mean elevation to maximum elevation reveals a transite state of landscape adjustment to high uplift rates. Stable state landscapes including basins and plateaus with low incision rates have smoother local relief curve where the swath curves are merged (Perez-Pena et al, 2017: 137). Based on the exported diagrams, higher values of enhanced transverse hypsometry index (Thi*) occurs when the third quartile and in some points mean elevation is closer to the maximum. When swath curves meet the flat areas of Zagros foredeep (Dezful embayment) merging together, Thi* values keep a constant value of about 0.5.

Results show that in swath profiles with the direction perpendicular to the Zagros trend, comparing areas with different uplift and incision is better possible. In both perpendicular and parallel swath profiles, high values of the enhanced transverse hypsometry integral (THi*) introduce a young relief that is being incised by a drainage network with steep valleys. These high values of THi* can be observed in the location of anticlines of Zagros simply folded belt unit and as well as in intersections of main faults with swath profiles in most swath diagrams. High local relief and wider variation of curves in most swath profiles, except the end parts of the southwest of the region, can characterize a dissected landscape exposed to high incision or uplift.

Instead of focusing on how development affects ecosystems, the ecosystem service approach focuses on how ecosystems affect development. By quantifying the water production service in a basin, it is possible to determine the amount of water production in different uses of the land and use this information to apply better management decisions in line with the potential of the region. The provision of this service depends on the characteristics of the watershed such as topography, vegetation and land use, climate and other parameters governing the provision of services. Various tools and models have been developed to study these services to help authorities make appropriate decisions for ecosystem management. These tools are divided into two general categories, traditional hydrological tools and ecosystem service tools, which are service-specific tools. InVEST tools focus on the final services of the ecosystem and map the services and in this research has been used to serve the water production of the study area.

The study area of the coastal strip of Bandar Abbas from Bustano (west) to Bandar Abbas airport (east) is 69 km along the coastline. Therefore, to make the research comprehensive, the smallest hydrology unit in the area or catchment area where this area of Bandar Abbas city is located was selected. In this research, the water production model from the model set, InVEST 3.8.9 was used with the aim of plotting the possible future of the study area. This process consists of two general steps, first processing and preparation of satellite images, then modeling water production with InVEST model. Landsat satellite images (5 and 8) were used to prepare mapping images of the study area and after performing radiometric, atmospheric and ground reference corrections (by Ye and Grimm method, 2013) And the classification of the images was achieved with the maximum likelihood similarity algorithm (by Shrestha et al method. 2018).

The watershed area that has been selected as the study area includes three sub-basins with a total area of 272,806 hectares. In this section, the land use of the study area was divided into 5 categories: water, urban, agricultural, arid and grassland. And modeling was done first in the year 2000 as the base year of comparison for subsequent years and then in 2020. In the year 2000, the area of human-made floor is 10721 hectares, water is 671 hectares, agriculture is 11285 hectares, arid lands are 150123 hectares and grassland cover is 100003 hectares. The percentages of each land use are 3.9, 0.24, 4.1, 55 and 36.6, respectively. These figures for 2020 are: human-made land uses with 6.2% and water, agriculture, arid and grassland land uses with 0.62, 8.7, 50 and 34%, respectively. It can be seen that human-made, water and agricultural uses have increased and pasture and wasteland uses have decreased. Examination of the water production map shows that it increased from a maximum of 81 mm in 2000 to 70 mm in 2020. Also, by comparing the maps, the amount of water production in the study area had decreased from 7.143.433 cubic meters to 5.463.450 cubic meters in 2020, which indicates a decrease of 23%. The results are also visible at the sub-basin level. In 2020, the reduction of water production in sub-basins 12, 11 and 13 demonstrated a decrease of 24, 21 and 27%, respectively.

Comparing the land use cover of the base conditions in 2000 and 2020 revealed that man-made, water and agricultural land uses have increased and grassland and arid land uses have decreased. Comparing the rainfall maps indicated that the rainfall situation in the study area is increasing from south to north and the lowest rainfall in the southwestern part and the highest rainfall in the northern and eastern parts of the study area and for both periods of rainfall status are almost the similar.The InVEST water production model estimated the ecosystem water production volume in the whole basin to be more than 7 million cubic meters in 2000 and more than 5 million cubic meters in 2020, which represents a decrease of 23%. The map of water production by sub-basin shows a decrease in all sub-basins in 2020 compared to 2000, and among sub-basins, sub-basin has the highest and one lowest production, and this is the same in both periods.
According to the obtained results, the study area has severe water stress based on water production and basin area. In adiiton, by considering the importance of water and taking into account other factors such as climate change, rainfall reduction, change in rainfall type, global warming, increase in evaporation, and population increase, we need to decide and invest in supply, transmission, and increase of water efficiency. This is an important endeavor considering the factors changing the type of rainfall, which means the intensity and aggressive nature of local rainfall in the study area and its role to start the separation and transfer of soil particles by runoff. The results of the present study also shows lower overall rainfall in 2020 compared to the year 2000, which affects the inherent sensitivity of the soil and makes it more susceptible to erosion, which, in turn, doubles the importance of addressing this issue.
Due to the fact that water production in the whole basin has severe water stress, and the overall decrease in rainfall in 2020 compared to 2000, this situation will have a greater impact on the inherent sensitivity of the soil and predisposes it to erosion.This is an important issue considering the intensity factor and the aggressive nature of local rainfall in the study area and its role in initiating the separation and transfer of soil particles by runoff which exposes the study area to more severe water erosion. Also, considering the spatial pattern of precipitation changes in the northern parts of the watershed, this area will be more erodible, and due to the impact of wind erosion on water erosion, the results of investigations for this section are useful to help study wind erosion and increase fine dust.

Landslides are one of the most alarming disasters that can cause severe damages to human lives and properties each year. This natural phenomenon can destroy or damage a variety of engineering and human structures, including residential areas, roads, gas pipelines, water and power lines, forests and pastures, agricultural lands and mines. In addition, the social and environmental impacts of this phenomenon such as adverse social effects and increase in the sediment load of rivers should not be overlooked. Due to its mainly mountainous topography, high tectonic activity and seismicity, diverse climatic, and geological conditions, Iran has mainly natural conditions to create a wide range of landslides. So, along with the many natural benefits that exist, the risks involved should not be ignored. The existence of large Zagros faults, alternation of calcareous hard layers and loose marl shale layers in the large anticlines have created favorable conditions for instability of natural slopes throughout Lorestan province. Therefore, this study aimed to prioritize the factors affecting landslide and its risk zonation by using the entropy method in the Ahmadabad basin, Lorestan province.

In this study, 8 factors including slope, lithology, precipitation, land use, elevation, and distance from springs, roads and streams were prepared and quantified as factors affecting landslides. According to the characteristics of the landslides of Ahmadabad basin and expert opinion, each layer was given a score of 1 to 9 based on its importance in occurrence or intensification of landslides. After the classification of layers, the entropy matrix was created. Calculating the entropy matrix and the total weight of the factors (wj) gives the coefficient of occurrence of landslide risk (Hi). The entropy model is expressed as follows.
Ej=-Ki=1npi, jInpi,j                                                                                                                            (1)
pi,j=ri,ji=1mri,j                                                                                                                                           (2)
where, Ej is the entropy value, pij is the decision matrix, and rji is the weight value of each layer, M is the number of landslides, and K is a constant coefficient.
After providing the decision matrix and obtaining the value of Ej, the value of Vj is obtained from Eq. 4.
k=(In m)-1                                                                                                                                         (3)
Vj=1-Ej                                                                                                                                            (4)
Vj is the degree of uncertainty deviation. The Eq. 5 is used to calculate the final weight of all factors (wj).
Wj=Vjj=1mVj                                                                                                                                           (5)
After that, the landslide hazard zonation in the studied basin is evaluated using Eq. 6.
Hi=i=0nWj*ri,j                                                                                                                                (6)

In this research, a bipolar scale is used to convert quantitative and qualitative values. After providing the entropy matrix and converting these criteria to an integer, by calculating the relationships and converting the quantitative values to quantitative ones, the information content in the matrix was first obtained as (pi, j) and, then, the value of Ej is calculated for each factor. The values of Vj and Wj were also calculated using Eqs 4 and 5, and, finally, the regional model of the landslide hazard rate was obtained based on Eq. 6.
Based on the relationship of the landslide risk coefficient, a landslide hazard zonation map has been prepared for the studied basin. Based on the results and in respect with 14.6%, 28.8%, 28.8%, 20.0% and 7.8% of the area were classified as very low, low, medium, high and very high, respectively. Then, the landslide area in each hazard class was determined and the accuracy of the entropy method was estimated using the additive utility method (AUM). The results showed that the accuracy of the method used in predicting landslide hazard zones is about 86%.

In this study, 8 factors have been investigated for zoning landslide risk. Prioritizing the factors affecting landslide using the entropy method shows that three factors including lithology, land use and slope with 24.1, 16.8 and 13.5% of impact have the most important role in landslide occurrence.
Based on the results, more than 56% of the study area is located in medium to high-risk zones, indicating a significant potential for landslide hazards. These zones are mainly located to the north and west of the region, which can be attributed to the sensitive lithology and slope susceptibility of these areas to landslide events. Also, according to the results, 10 villages are located in high to medium risk zones and most of the roads are located in these risk zones.
Therefore, it is necessary to avoid any constructions and increase safety of the existing structures in these areas. The results of the present study showed that the entropy method is suitable for identifying hazardous areas, so it is recommended to use the obtained results in land use decision making and management and regional planning.

Remote sensing and Geographic information system have the capability of detecting and/or monitoring the features of the earth’s surface using satellite images and have different radiometric, spectral, spatial, and temporal resolutions. These technologies resolutions have several advantages in order to minimize the time and cost  of extracting Land cover and Land use (LULC). In addition, the remote sensing provides important and different kinds of remote data sources to extract LULC information. Remote sensing data are widely used and applied to perform classification of LULC in the world. Remote sensing data has the ability of updating information about all of the features located on the earth’s surface. The classification of remote sensing imagery is an important method in order to determine the LULC information. Classification approaches are divided into two categories:  pixel base and objected oriented base classifiers. The present study's aims are conducting land use classification by making a comparison between different algorithms in Taham watershed in Zanjan province.

In this research, Landsat8 satellite images (25 July) were used to perform preprocessing and processing steps. Geometric, radiometric and atmospheric corrections were used to eliminate the image noise. In the next step, for the existing uses in the region, first, field samples (160 educational points) were collected separately for each use in the region by using field visits and the Global Positioning System (GPS). Educational samples were divided into two categories, 70% of them were used for classification and 30% were used to accuracy of classification methods. After applying the image corrections according to the studied algorithms for each algorithm using EVVI 5.3 software and educational samples, the land use role for the study area was prepared. According to the sampling, five classes in the study area include agricultural land, rangeland, barren land, residential areas and waterbody areas. To evaluate the accuracy of the classified maps, the error matrix was calculated by using ENVI software. For this purpose, in the present study, the coefficients of Overall Accuracy, Kappa Coefficient, Producer Accuracy, User Accuracy, Commission and Omission had been used.

The aim of this research was to classify and map land-use/land-cover of the study area using remote sensing and Geospatial Information System (GIS) techniques and includes two sections, namely Land use/Landover (LULC) classification and accuracy assessment. In this study, the supervised classification and four algorithms (including SVM, MLC, MDC and MC) were used and then five classes for the study area including agricultural land (3.26), rangeland land (89.85), residential land (0.15), waterbody (1.19) and barren lands (5.55) were extracted. Also, the results showed the SVM algorithm with overall accuracy (98.24), kappa coefficient (0.969) as the most accurate, MDC algorithm with overall accuracy (94.36) and kappa coefficient (0.9) as the last priority in this study. According to the results of Tables 2 and 3, it can be seen that the percentages related to the five land use classes (residential areas, irrigated areas, agricultural lands, rangelands and baire lands) are mostly above 90%. This indicates that a high percentage of the pixels associated with these uses are properly classified. This study also presents essential source of information whereby planners and decision makers can use to plan sustainably measures for the environment.  

Today, the use of LULC mapping is a vital issue for collecting data in urban planning, comprehensive watershed management, identification of effective factors, and environmental monitoring. The use of remote sensing technology with different satellite images is recommended as the best strategy for preparing LULC maps. By using different systems the limitations and capabilities of these images can be identified. The purpose of this study was to generate LULC thematic maps by comparing different algorithms, using maximum likelihood, minimum distance from mean, Mahalanobis and Support vector machine in Tham watershed in Zanjan province by applying Landsat 8 images. After performing all of the necessary corrections with the steps of preprocessing, processing and analysis of satellite images, four different algorithms were used to classify the satellite images. Support vector machine algorithm with an accuracy equal to 98.24% and kappa coefficient with an accuracy equal to 0.969 has the highes accuracy among other algorithms.  Of course, the maximum likelihood algorithm with 97.45% overall accuracy and kappa coefficient equal to 0.961 have the highest accuracy in extracting land use maps and the slightest difference with the support vector machine algorithm, respectively.  In other words, it can be said that the two support vector machine algorithms and the maximum likelihood have a high level of accuracy in extracting the land user maps. The two algorithms of Mahalanobis distance and minimum distance from the mean were ranked next.

Today, the increasing population and, consequently, the demand for agricultural products have caused the natural cover of land, especially forests and pastures to be destroyed by humans at an alarming rate to become agricultural land; even in many areas due to lack of water and nutrients, vegetation growth is limited. Declining vegetation worldwide due to human activities such as overgrazing and deforestation reduces permeability and consequently increases runoff and can reduce soil particle adhesion and predisposes fertile soil particles to erosion. Soil erosion in managed ecosystems such as crops, pastures, or forests, as well as in natural ecosystems leads to extensive damage. It also reduces the infiltration capacity due to runoff and reduces soil organic matter and thus valuable soil nutrients. At the same time, it significantly reduces the diversity of plant and animal species. To this end, controlling soil erosion is one of the most important goals in water conservation and management programs. Vegetation can be a very important tool to control water erosion and regenerate the ecosystem. Vegetation reduces the shear stress by increasing the roughness and decreasing the water flow velocity, and the hydraulic resistance created by the vegetation causes the absorption and deposition of suspended sediments. Vegetation and its associated factors on a long-term scale also play an important role in modifying the hydrological properties and soil erodibility and sediment load. The role of vegetation in reducing runoff and soil erosion in different studies has been proven. However, the effects of different vegetation compositions have not been studied extensively in runoff and soil erosion control. Accordingly, the present study was planned to investigate the effect of different compositions of graminea and bushes with different coverage percentages on runoff and sediment components.  

The study area is part of the natural rangelands located in the surroundings of the University of Mohaghegh Ardabili, Ardabil, NW of Iran. A total of nine treatments from different vegetation compositions including low-height graminea predominance (T1), the composition of dense bushes with graminea (T2), bushes with low-height and medium-distribution (T3), sparse bushes mostly with low and medium height (T4), the composition of sparse bushes with graminea (T5), dense bushes in upper parts (T6), low-height bushes with very low distribution (T7), dense bushes with almost uniform distribution (T8), and no vegetation cover (control) (T9) were selected. In addition, the effect of different percentages (zero, <40, and 40-60) of vegetation on changes in runoff and sediment components was investigated. It should be noted that the vegetation in the control plots was removed at the soil surface in the desired plots as much as possible. Considering that, 27 field plots surrounded by galvanized sheets with an area of 2 m2 with a slope of 12-15% were installed. Study treatments with three replications were designed in a completely randomized block with help of field plots with dimensions of 2*1 m and an approximate slope of 12-15%. This study was performed using a rainfall simulator with an intensity of 32 mm h-1 and a duration of 18 min. The plots were placed in a rectangular in the direction of the slope, using 15 cm high metal sheets, five cm of which were sunk into the soil so that the generated runoff did not seep out of the plots. Totally, five components including time to runoff, runoff volume, runoff coefficient, soil loss, and sediment concentration were measured for each plot.

The results showed that the effect of different vegetation compositions on runoff and sediment components was significant (p-value <0.0001). The maximum time to runoff (1388.33 seconds) in treatment T4 and the minimum runoff (0.41 L) and runoff coefficient (2.14%) in treatment T2, respectively with +98, -82, and -82 % change compared to the control treatment has been obtained. In addition, the minimum soil loss was equal to 1.30 g in treatment T2 and the minimum sediment concentration was equal to 6 g l-1 in treatment T8 with -86 and -69% change compared to the control treatment, respectively. Statistical analysis of the effect of different vegetation percent also showed that there was a significant difference between the mean time to runoff and sediment concentration (p-value<0.001) and a non-significant difference between the mean runoff amount and coefficient (p- value<0.73), and soil loss (p-value<0.15). In general, treatments with less than 40% vegetation were more effective in controlling runoff components and treatments with vegetation between 40 to 60% were more effective in controlling sediment components.

The runoff threshold in different compositions and percentages of vegetation has a significant difference compared to the control treatment. Vegetation in both groups of <40 and 40-60% by delaying the formation of runoff has increased water permeability in the soil. Low-height graminea predominance (T1) treatment, the composition of dense bushes with graminea (T2), bushes with low-height and medium-distribution (T3), and sparse bushes mostly with low and medium height (T4) had the maximum effects (more than 80%) in increasing time to runoff. Although the treatment of the composition of sparse bushes with graminea (T5) was not effective in increasing the runoff threshold and reducing the amount and coefficient of runoff, it reduced the soil loss and sediment concentration by 21 and 57%, respectively, compared to the control treatment. Therefore, it can be concluded that if this type of erosion management strategy is adopted, this type of composition can also be considered. While it is not a suitable management option for runoff and flood control, treatments T4, T3, T2, and T1 should be used effectively. In addition, treatments with <40% vegetation cover had better performance compared to treatments with 40-60% vegetation in improving runoff components; nevertheless, 40-60% of vegetation with a slight difference has played a better role in improving erosion and sediment components. Previous research has confirmed that soil loss processes due to water erosion are closely related to the runoff process. Compared to runoff reduction, vegetation treatments have provided better benefits in reducing erosion and sedimentation. For future studies, the morphological effects of vegetation types on the hydrological and hydraulic properties of degraded soils could be investigated.

Changes in the river duct, erosion and marginal deposition are natural processes of alluvial rivers; on the other hand, the development of human activities, such as sand making, construction along the river, and the protection of coastal lines and land use changes have led to a change in the dynamics and rivers' morphology (Grigory, 2006). Human activities cause more pressure on the river and the destruction of the riperin area (the area covered by the plant along the river) and, consequently, lead to the change of the river ecosystem (Lee, 2005). Therefore, lateral erosion and river channel changes are among the environmental, economic and social problem that often cause irreparable damage to residents and riverside facilities (Jav, 2008). Lateral erosion is one of the major causes of uncontaminated water resources and increasing sediment load in many rivers. Increased erosion not only increases the sediment load but also causes the river's instability and changes the flow type and channel pattern (Hossein Zadeh et al., 2017).

The total area of Kahoo Basin is 193.40 km2 and the length of its river is 41.41 km. Based on the geological maps, Kahoo Basin is divided into two parts of the mountain and alluvial fan. For the study of river morphology data and physiography of the basin, topography maps of 1/100000 (Ministry of Transportation) and 1/500000 (Golmakan, Geographical Organization of the Army, 1894) have been used. By using Landsat satellite images base maps are created and other indices and plans derived from field observations are obtained. Also, graphs and maps are mapped using Arc GIS software. The main objective of this research was to investigate the role of lateral erosion in the main channel bed of Kahoo alluvial fan. For this purpose, in the main channel, eighty profiles were sampled from proximal to distal of the alluvial fan.

The morphology of the main channel indicates a braided-type in most sectors at the beginning, which only in three intervals around the Devin and Shahniyaz villages changes to anastomosing-type. The estimated length is 1.56 Km. Also, the width of the main channel shows that the river's width is decreasing downward. To study the river bed width variations, using the ARC GIS software, the main channel of Kahoo alluvial fan was divided into 4 groups of less than 10 meters, 10-25, 50- 25, and 50-100 meters. Studies show that the maximum river route is 12.8 km in a transverse class less than 10 meters. The transversal classes are 10-25, 41.4 km, 25-50, 7-10, and 50-100 km long, 0.5 km long. The widest part of the river bed is 19/79 meters wide near the Hashem Abad village and the narrowest part of the bed is about one-meter-wide near the village of Devine at the end of the study period. In general, the average width of the river studied is less than 10 meters.

Sedimentation and erosion are the two main processes in the evolution of Quaternary massive alluvial fans, the function of which can be a function of technical controlling factors, climate, base surface and bedrock composition, and index of flood volume and amount of sediment entering the alluvial fan (Naipal et al., 2020). Kahoo alluvial fan is located in the northwest of Khorasan Razavi province in the Mashhad plain and in the Kashfarud catchment area, which is one of the large basins of Qaraqoom. This study studied the plain section. From the geomorphological point of view, the canal of this river, except for the short distance, which is anastomosing, is more than the cut type, so erosive factors will play a much greater role in controlling the canal (Yang et al. 2007). The results of canal erosion were examined in two parts of the side and the bed.
The study of lateral erosion shows that the average depth of terraces is between two to five meters and the intensity of erosion is furrow and moat type, so the river class is H2T3. It should be noted that it is more visible on the left bank of the H3T1 class and on the right bank of the H3T4 class, which indicates more erosion at the left bank arches, and the river will probably lean to the left. Accordingly, this river can be considered asymmetric in terms of lateral erosion (Gopmbrtva et al., 2020).
The results of bed erosion study indicate that in most sections, the cross-sectional dimensions have not reached the final equilibrium and the depth and slope of the river have less changes than the river width, which shows that bed erosion is less than wall erosion. Therefore, the riverbed can be considered close to equilibrium in most places (Lacey 1959).
Field observations also confirm that lateral erosion, especially in the outer part of the river arch, is more. Also, based on the satellite image of Kahoo alluvial fan and the changes of the main channel, especially in its middle and ending sections, the migration of the channel to the left can be seen. Therefore, further erosion of the left wall can be considered as the most important factor in the morphology of the main channel of this alluvial fan today, which has caused changes in slope, width, etc.

   Due to the fact that soil erosion in the sloping lands of Chehelchai watershed in Golestan province is severe and has a negative impact on soil fertility and productivity for food production, it is necessary to use more soil conservation measures than other areas. In this regard, several measures have been conducted for soil conservation by the related government agencies, such as the Agricultural Jihad Organization and the Department of Natural Resources and Watershed Management. The Agricultural Jihad Organization has extensively explained the consequences of continuous plowing on land slopes, and has provided guidelines for promoting practices such as terracing, tree planting, and minimal tillaging. In addition, there have been little successes in adoption of terrace methods, plowing in the opposite direction of slope, minimal tillage, as well as a combination of these methods. Therefore, the present study intends to use Theory of Planned Behavior (TPB) and recognition of influential factors on the adoption of soil conservation methods in sloping lands to provide basic information that is consistent with the reality and conditions of the region in order to prevent the waste of natural resources, especially farm soil.

The present study adopts a cross-sectional survey research. The tool for data collection and measurement of variables was a questionnaire that was developed according to the framework of TPB. Thus, the questionnaire is divided into four main parts, including: 1) personal characteristics; 2) characteristics of the production system; 3) soil erosion status and 4) items related to measuring soil conservation behavior that has been developed based on TPB framework. The target population consisted of 1700 landholders from 26 villages in the area, of which 313 were selected based on Krejcie Morgan table as a sample and were randomly stratified. Validity of the questionnaire was obtained through a group of experts and its reliability was confirmed by calculating Cronbach's alpha coefficient (mean coefficient = 0.78). The gathered data were analyzed by SPSS Version 23 software.

The results showed that a considerable proportion of land owned by farmers is sloping and under continuous cultivation of various crops. Based on the results of the research, farmers assessed the high level of erosion of their fields and expressed great concern about the consequences of erosion on the field and its fertility loss. The presence of heavy rains, followed by the occurrence of destructive floods and the accumulation of sediments in the lowlands, which has challenged the conditions for agriculture, have played a major role in creating this concern. Despite these concerns, most of the respondents were not familiar with erosion control methods and more than half of the farmers did not believe in the effectiveness of soil conservation methods in controlling erosion of agricultural lands. The results of Mann-Whitney test showed that the soil conservation behavior was connected to land type, type of cultivation, concern of erosion as a problem in the field, familiarity with soil erosion control methods at 95% confidence level. In addition, people who participated in extension classes related to soil conservation had better performance in adoption of soil conservation measures. Based on the findings of Kruskal-Wallis test, there was significant relationship between soil conservation behavior and erosion status and belief in the effectiveness of soil conservation methods. It was also found that he lower the erosion status on land and the greater the belief in the effectiveness of soil conservation methods in controlling erosion, the better the behavior of adoption soil conservation measures. The correlation results indicated that there is a positive and significant correlation between the adoption behavior and the variables of total land area, sloping land area and cultivation area. Also, the results of path analysis showed that the variables of attitude (0.148), subjective norm (0.262) and behavior control (0.412) have a direct and significant effect on the dependent variable of adoption behavior. These variables implied that 51.6% of the changes in the variance of dependent variable was explained by two variables of intention and behavior control.
 

Due to heavy rainfall and subsequent destructive floods upstream, there is extensive concern about the consequences of erosion among farmers in the sloping lands of Chehel-Chay watershed in Golestan province. There is also a favorable attitude towards soil conservation. However, due to little familiarity with methods of soil erosion control, it is necessary to take many extension and educational measures. Therefore, offering training material and skill promotion workshops about soil conservation should be considered. Moreover, facilitating meeting and contact with local extension agents is necessary for promoting their knowledge and skill about soil conservation. Furthermore, providing financial incentives and low-interest and long-term loan for farmers are effective ways to encourage formers to adopt and use more soil conservation measures.

Dust storm is a great challenge worldwide, especially in Iran. West and southwest regions of Iran are more exposed to dust storms due to their geographical position and neighboring countries such as Iraq, Syria, Jordan, Yemen, and Saudi Arabia. Today, scientists have proposed different ways to control wind erosion and dust storm; for instance, construction of live and non-living windbreaks to decrease wind velocity near the ground or covering soil surface through natural or chemical materials to prevent soil particles removal by winds in different intensities. Chemical polymers are one of the most effective methods to reduce soil erosion and dust. In recent decades, using synthetic polymers such as polyvinyl acetate has been considered in order to increase aggregate stability and soil stabilization. These polymers bind the soil particles to make larger aggregates and consequently increase aggregate stability. Moreover, the investigation of different mulches efficiency is essential in dust storm control and sand dune fixation. Therefore, the aim of this project was evaluating the efficiency of biocompatible polymer to decrease dust storms in laboratory conditions.

This project was conducted near Mehran city (Mohsen Abad plain) in Ilam province in 2019. In order to perform soil physical and chemical analyses, soil sampling was randomly carried out from soil surface (0-30 cm) in different places in the study area. These analyses consist of soil texture, soil saturation moisture, soil pH, EC, lime, soil organic matter, and aggregate stability. Moreover, to evaluate polyvinyl acetate, soil loss by wind tunnel, compressive strength, penetration and impact resistance are tested on samples. In this regard, soil samples collected in the study area were poured in trays with 35× 35× 3 cm dimensions. By considering four levels of polymer (C1=1, C2=1.5, C3=2, and C4=2.5 percent) with control (C0) in three replicates, 30 treatments were prepared. In order to evaluate polyvinyl acetate mulch, all tests consist of a wind tunnel simulator test, aggregate stability, permeability and impact resistance were performed after 28 days, and the results were studied. The data were analyzed by conducting one-way analysis of variance (ANOVA) and means comparisons were calculated by using Duncan test at significance levels of P ≤ 0.01 and P ≤ 0.05.

According to the results, the most and the least aggregate stability were observed significantly (P<0.05) in C4 treatment with 85 % and control with 18 %, respectively. The wind tunnel test showed that the highest soil loss belongs to control treatment (C0 =without mulch) with significant differences from other treatments. In terms of compressive strength, C4 treatment with 2.4 kg/cm2 had the highest compressive strength against the penetrometer device compared to other treatments. In addition, the result showed that by increasing the polymer concentration, the penetration rate of polyvinyl acetate polymer significantly decreased into the soil. Furthermore, increasing the polymer concentration, increased impact resistance compared to the control. In addition, based on the results, hit resistance rose by increasing polyvinyl acetate concentration so that the least and the highest hit resistance were observed for control treatment (C0: 3 cm penetration in the soil surface) and C4 (1.35 cm penetration in the soil surface) treatment, respectively.

One of the important soil physical properties is aggregate stability which can protect soil against erosion and erosive forces such as wind and rain. Based on the results of aggregate stability test, by increasing polyvinyl acetate concentration on soil surface, this factor improved significantly. Polymers bind primary soil particles together to form secondary particles or larger aggregates, which in turn increase aggregate stability. In soil conservation studies, wind tunnel simulation is used to monitor different mulch effects on wind erosion. In this study, the least soil loss is found when polymer is used, the reason can be explained by the fact that polyvinyl acetate cover soil surface and avoid wind contact with soil surface directly. Soil compressive strength depends on cementing agents directly and PVA in this study acted as a connection agent for soil particles. Based on the results, by increasing PVA amount, the compressive strength of the soil increased. Based on the given results of this research, polyvinyl acetate mulch from 2 to 2.5 concentration percent increases compressive strength and aggregate stability in laboratory conditions. Furthermore, this polymer attaches soil particles together and penetrates in the soil to increase compressive strength and influence dust storm control.  In general, polyvinyl acetate polymer can be used as a suitable mulch by creating a good physical and mechanical conditions in the soil. Nevertheless, it should be considered that these results have been obtained in the laboratory conditions. So, for application of PVA in the natural ecosystem such as arid land conducting further is research required.