فصلنامه پژوهش های فرسایش محیطی
سال چهاردهم شماره 1 (پیاپی 53، بهار 1403)

Floods pose significant risks as natural disasters on a global scale. In addition to climate change, anthropogenic activities have exacerbated the damaging effects of flooding over the past decade. Findings indicate that over 91 billion hectares of land in Iran are susceptible to flooding. Extensive hydrologic records reveal a total of 467 flooding events in the country up until 2002, contributing to a loss of 630 lives between 1982 and 1992. These alarming statistics underscore the necessity of studying and analyzing floods, as well as mapping inundation areas, in order to mitigate potential damage associated with future flooding events. One particular region in western Iran that has been heavily affected by recurring floods is the Kashkan River. This river traverses numerous urban and rural areas that are prone to annual flooding. Although various methodologies exist to investigate floods and identify areas susceptible to inundation, many of these approaches require data that may not be readily accessible. Consequently, this study employs the Height Above the Nearest Drainage (HAND) model to examine the flood-prone sections along the Kashkan River. Unlike other methods, the HAND model solely relies on a Digital Elevation Model (DEM), making it a promising and accurate technique for mapping inundation areas. By utilizing the HAND model, this research aims to identify specific sections of the Kashkan River that are prone to flooding. The findings of this study will contribute to a better understanding of flood dynamics in the region, enabling the development of effective strategies to minimize potential damage.

In order to examine the areas that are prone to flooding, we employed the Height Above Nearest Drainage (HAND) model. This model was originally introduced by Rennó et al. (2008) and operates by utilizing a Digital Elevation Model (DEM) to compute the distance between a grid-cell within the topography data and the nearest cell along the stream it drains into. By considering cells with HAND values below a specific threshold as inundated, we can identify areas that are susceptible to flooding. Notably, the HAND model offers the advantage of being raster-based, eliminating the need for the construction of cross-sections, which is a requirement for alternative techniques like HEC-RAS. For our investigation, we employed the Shuttle Radar Topography Mission (SRTM) DEM, which possesses a resolution of 30 meters. To validate the findings obtained from the HAND model, we employed flood maps generated from Sentinel-1 Synthetic Aperture Radar (SAR) data from March 2019. These flood maps were created using the Sentinel Application Platform (SNAP) software and the OTSU thresholding method. This method allows us to distinguish flooded areas within the study region and validate the results obtained from the HAND model.

The findings from this study indicate that a significant portion of the study area, encompassing 54.49 square km, is classified as highly flood prone. Additionally, an area measuring 31.78 square km is categorized as flood prone. Based on the HAND maps, it is evident that more than 30 percent of the study area is susceptible to flooding with varying intensities. The outcomes further reveal that the majority of both rural and urban regions situated alongside the Kashkan River are located within highly flood prone sections. Moreover, a comparison between the flood maps derived from Synthetic Aperture Radar (SAR) and the HAND results demonstrates that the HAND model successfully identified and classified the flood area in March 2019 as highly flood prone and flood prone. By examining the cross-section along the river, it becomes apparent that the inner banks of meanders are more susceptible to flooding when compared to the outer banks. Cross-section 1 analysis revealed that the sections with a high susceptibility to flooding are situated at higher elevations when compared to the maximum flood level observed in March 2019. This implies that in the event of more sever floods in the future, a larger portion of the areas along cross-section 1 will likely to be inundated. Additionally, the analysis demonstrated that during elevated flood flows, the outer bank of the meander is more prone to flooding compared to the inner bank. Similarly, in cross-section 2, the outer bank of the meander exhibits a greater extent of highly flood-prone areas compared to the inner bank. Furthermore, cross-section 2 findings indicate that the flood flow during March 2019 did not reach the upper limit of the highly flood-prone category. In contrast to the previous cross-sections, cross-sections 3 and 4 primarily experienced flooding along the inner bank of the meanders, and the HAND model also classified them as highly flood prone. These results suggest that the distribution of inundation in the Kashkan river is predominantly influenced by the underlying topography.

The findings indicated that both rural and urban regions situated along the Kashkan river exhibit a high vulnerability to flooding, with a propensity for inundation during flooding events. The results revealed the efficacy of the HAND model in accurately identifying the flood-prone segments of the Kashkan River. Analysis of cross-sections along the river revealed that the inundation patterns in mountainous meandering rivers are predominantly influenced by the underlying topography. Overall, the HAND model represents a swift and precise approach for delineating areas at risk of flooding, thereby assisting authorities in enhancing planning strategies and implementing effective measures for mitigating damages.

Urban rivers originated or flew in urban area, Man-made canals which have characteristics of natural rivers, are types of urban rivers as well. The urban river landscape is an important physical element and a kind of ecological corridor in urban landscapes. River corridors play important roles such as providing habitats, acting as filters and barriers, being water sources and water sink and etc (Forman and Godron, 1986). They also increase supply water resources and transportation ways, urban landscape diversity. Moreoverurban rivers enrich the life of urban citizens and contribute to stability, comfort, and sustainability in urban development (Cook, 1991; Baschak LA, Brown, 1995). Due to heavy disturbances throughout the urbanization process, urban rivers have become one of the most intensively influenced areas in the interaction between humans and natural processes. Human activities have drastically changed the structure and function of urban river landscape (Yue, 2012). Many methods have been presented to evaluate and monitor the morphology of rivers, which have variations in terms of concepts and goals. One of the most recent of these methods is the Morphological Quality Index (MOI) presented by Rinaldi et al. in 2013. MQI method was assessment the morphologycal quality of many rivers such as Ahr river in Italy (Campana et al., 2014), Cecina River in Central of Italy (Rinaldi et al., 2017), 122 rivers in Greec (Stefanidis et al., 2022), Lawej river (Esmaeeli and Valikhani, 2014), Taleghan River (Nosrati et al., 2019 and Rezaei et al., 2023) all in Iran.

In this research, an attempt will be made to investigate the geomorphological condition of the Qarasu River in Kermanshah by using the Morphological Quality Index (MQI) and evaluate the ability of this index to analyze the geomorphological conditions of the urban river. Finally, according to MQI method the difference between the goals of geomorphologists and municipal planners and experts  are going to compare and analyze.According to Rinaldi et al. (2013) we assessed three different hydromorphological features, i.e.,Geomorphic functionality, which is based on the observations of fluvial landforms and processes.Artificiality, which expresses presence, frequency, and spatial continuity of anthropogenic structures and/or activities, which could affect the considered river morphological parameters;River channel changes.We then calculated the Morphological Alteration Index (MAI) as follows (Rinaldi et al., 2016) MAL=S totS max Where Stot is the sum of the scores and Smax is the maximum possible deviation for the given stream typology. The MAI is equal to 1 in a completely unaltered river, while it is equal to 0 in a completely altered river. The final step was the assessment of the Qarasu River morphological quality by means of the calculation, for each RR, of the Morphological Quality Index (MQI), as follows:MQI=1-MAL
Based on the MQI values for each RR, we defined the Morphological Quality Classes according to Rinaldi et al. 2016.

Firstly, we divide Qarasu river into 5 segments with variable reaches. In the next step, according to the evaluation parameters of each index in the MQI model, and using field visits, satellite images, and analysis of historical aerial photos, each of the study areas was classified into A, B, and C classes. Then the selected segments of Qarasu River in Kermanshah city were scored. Finally, by using the algebraic sum of the points obtained in each interval as well as the total scores of class C (the condition of the river is in a very bad state) and using relations 1 and 2, MAL and MQI indices were calculated for each interval. The results of examining the selected intervals according to the indicators measured in the Morphological Quality Index method are presented in Table 4. According to table 4, only the first segments of Qarasu River in Kermanshah is in poor condition and other segments of the study area are in good condition. It is noteworthy that fourth and fifth Segments are almost in the same conditions and their scores are equal to 0.76. The second segment has the highest score (0.79). Moreover, the field surveys showed that human activities such as construction waste were observed in the Qarasu River in the first and second segments. The goals and priorities of experts and planners of municipalities in urban areas are issues such as citizens' health and safety, protecting the city against floods, communication between the sides of the river, preserving the visual beauty of rivers and finally paying attention to the aspect of tourism. While in the purely geomorphological view of rivers, any interference and possession in the course of rivers is considered to disturb the balance and is not allowed (table 5).

Due to the supply of agricultural water in the region, the favorable weather and passing through the city of Kermanshah, changes have been made in the bed and channel of the Qarasu River. On the other hand, the bed of this river has changed with the passage of time due to the discharge of construction waste on the side of Qarasu River in Kermanshah city. Therefore, it is necessary to evaluate the Morphological Quality Index of Qarasu River in Kermanshah city. In this regard, Qarasu River in Kermanshah city was divided into 5 segments. The scores of ranges using the Morphological Quality Index method showed that the first segment is in poor condition and others are in good morphological conditions. Also, the field survey showed that in the second segment of Qarasu River, the dam of this river has been destroyed, construction waste in the river and there are grooves along the river. As a result, the Morphological Quality Index is not successful in identifying the condition of the second segment of the Qarasu River. It seems that this model should be used more accurately and sensitively in the evaluation of rivers in urban areas. It is suggested that during the planning regarding the restoration and protection of rivers in urban areas, in addition to the attention and use of structural methods, special attention should be paid to the natural conditions of the river channel in the upstream, the city environment and the downstream flow.

Water erosion is the result of interactions between various environmental factors such as topography, soil characteristics, climate characteristics, runoff and land use and management. Sediment production is highly dependent on runoff, so doubling the speed of runoff increases its leaching capacity and transportability up to five and six times. Knowing the effective factors in sediment production plays an important role in determining the amount of sedimentation of a watershed and understanding the phenomenon of erosion and its consequences, and it can be used in prioritizing the sub-basins of a watershed. The purpose of this research is to investigate the relationship between morphological characteristics and the amount of sediment production in the catchment area of the Gharasu River in Ardabil using principal component analysis and multivariate regression, in this regard, using 16 independent variables and 1 dependent variable in 13 sub-basins of the Gharasu River.

As one of the sub-basins of the Aras catchment basin, Gharasu catchment is located in the geographical coordinates of 47°31' to 48°47' east longitude and 37°47' to 38°52' north latitude. In this study, 1:100,000 scale geological maps, 1:25,000 scale topographic maps, and discharge and suspended sediment statistics and information of 13 hydrometric stations of Gharasu River sub-basin were used in the 50-year period from 1350 to 1399. In order to check the correlation between independent and dependent variables and to test the normality and normal distribution of data, Shapiro-Wilk and Kolmogorov-Smirnov tests were used in SPSS software. Also, in this research, the OLI Landsat 8 satellite images were used to extract the vegetation cover index (NDVI). For this purpose, step-by-step linear regression is used to determine the most effective variables and to determine the most appropriate statistical relationship between suspended sedimentation and the variables used, and principal component analysis is used to determine the most effective factors of suspended sediment production in the watershed.

In this study, the average annual suspended sediment of the basin was considered as dependent variable and other parameters as independent variables, and Pearson correlation method was used to check the correlation between independent variables and dependent variable. The variables of time of concentration, length of the main waterway, area, Slenderness ratio, perimeter and slope have a higher correlation with the amount of sediment production in the basin than other variables. Based on the models obtained from sediment correlation analysis, the amount of sediment produced with the concentration time variable had a positive correlation and was significant at the 5% level. The results of the analysis of the principal components show that the four factors of area, length of the main waterway, concentration time and slenderness ratio of the basin have an eigenvalue greater than 1, and the number of extracted factors is 4 factors. The first factor (area) has been able to explain 37.230 percent of the variance of all research variables. This value is 24.735, 16.950 and 9.849 percent for the second factor (length of the main waterway), the third factor (concentration time) and the fourth factor (slenderness ratio) respectively.

The present research was conducted with the aim of investigating the relationship between geomorphic parameters, vegetation and erodible formations of selected sub-basins of Gharasu basin with the average annual sediment. For this purpose, the statistics and information of 17 variables (16 independent variables and 1 dependent variable) were obtained for 13 sub-basins of Gharasu basin from the regional water of Ardabil province. The relationship between geomorphic parameters and annual precipitation was determined using stepwise multivariate regression method. The research results indicate that geomorphic parameters have a high correlation with the amount of annual sediment production and can be used in sediment prediction. Meanwhile, the variables of concentration time, length of the main waterway, area, slenderness ratio, perimeter and slope have a higher correlation with the amount of sediment production in the basins than other variables. Among these variables, the basin concentration time variable was used in the final step-by-step regression model and was selected as the sediment predictor variable. This variable alone can predict 98% of annual precipitation. In order to ensure the appropriateness of the data, the KMO coefficient was used to analyze the main components. The value of KMO = 0.78, as a result, the data will be suitable for factor analysis. The results showed that the four factors of area, main waterway length, concentration time and elongation factor could explain 88.754% of the variance of all research variables.

One of the important purposes of flood spreading plans is to feed groundwater tables and increase quality of these resources. One of the most important indicators for evaluation of artificial recharge plans is to examine their impact on quality of groundwater resources. The main aim of current research is to investigate effects of implementation of artificial aquifer recharge plan (Herat flood spreading) on ​temporal changes of groundwater quality parameters in the region.

    Harat watershed area is 1413 square kilometers in south of Yazd province. The location of flood spreading sites implemented at the end of Harat basin outlet and with an area of ​​490 hectares, which includes four implementation areas. In order to investigate and evaluate the effects of flood spreading projects on groundwater resources, statistics of parameters of 17 wells were used from the area of aquifer of Fathabad affected by these projects, based on available information, parameters of calcium, carbonate, magnesium, sodium, chlorine, and total dissolved solids and salt was extracted. The wells were classified into two groups, control and affected, based on their location relative to sites and the direction of flow in waterways of area. According to length of period, in order to evaluate the impact of water withdrawals and consequently impact of sedimentation on the efficiency of the sites, the entire period was divided into two periods so that 2003-2011 is first period and 2012-2021 is second period. Minitab software was used to check linear trend of average groundwater quality parameters. For this purpose, the average of all types of quality parameters of water resources, first and second periods were entered in software and the change process for each parameter was obtained. In order to investigate temporal trend of groundwater quality parameters, Mann-Kendall test was used at 95% confidence level and Sen's slope by XLSTAT 2019 Software.

The results related to time trend of water quality factors through Mann-Kendall method and Sen's slope showed that calcium factor among nine wells located downstream of the project, three wells have no trend and the rest have a negative trend. The results of checking trend of control wells showed that calcium had a positive trend in all but one well during statistical period under review. Factors of sodium, bicarbonate and magnesium in the downstream of projects often have a negative trend and also in the control area they often show a positive trend, but factors of salinity, chlorine and total dissolved solids in the control area do not have the same situation as other factors. So that the number of wells without trend in the control range is more than the rest of the factors. This means that the condition of the aquifer in terms of three indicators is neutral and does not have a negative or positive tendency, but the investigation of trend related to affected area showed that flood spreading projects have been able to improve the status of these factors, which are part of the important factors affecting agricultural water. lead to improvement. In order to investigate effects of flood spreading projects, at the beginning and after several years, linear trending of the average factors was done in two time periods. Due to lack of data in the last of years of implementation of flood spreading to evaluate effectiveness of groundwater quality from flood spreading project, the number of available years was divided into two almost equal parts so that impact of these projects can be investigate in the initial period and after a few years. The results of linear trend of the first and second periods showed that total dissolved solids and calcium were decreasing with a high slope in the first period, but in second period and after a few years, effectiveness decreased, but it is still decreasing with a gentle slope. Bicarbonate and magnesium factor have had an increasing trend in first period, and in second period, magnesium has decreased towards a negative slope, but bicarbonate follows an increasing trend with a higher slope than in first period. In the case of other factors such as salinity, chlorine, sodium, trends are almost similar to each other. So, in the first period, they have decreased with a slight slope, but in second period, this slope has increased proportionally. This means that the infiltration of flood water through these projects has been able to improve status of all factors except for bicarbonate, but the passage of time has left different effects on the manner and extent of effect, which requires more detailed investigations.

According to results of investigations of time trend of various factors in this region, flood spreading has been able to have a positive effect on quality of groundwater. So that in determining trends of whole aquifer, except for bicarbonate factor, which had a positive trend, in other factors, there was a decreasing trend and no trend, which indicates positive effect of flood spreading on the control of quality factors. The results of this research showed that state of trend of all factors in some wells of witness area showed an increase and, in some wells, there was no trend, but in the affected area (downstream) all factors had a decreasing trend. The location of wells and distance from the waterways and flood spreading sites have a great impact on the vulnerability of wells. So that B9 well, which is located in the farthest part of the affected aquifer and is far from flood spreading sites, is among wells that had the most negative trend in most factors. Also, B3 and B2 wells are among wells that have the highest decreasing slope. Investigations showed that B9 well was located at a very short distance from the main waterway and B2 and B3 wells are also located near the distribution sites in addition to position relative to waterway and are affected by several flood distribution sites. So, distance of wells from waterway and the location of the sites can be very effective.

Sand dunes are one of the most important landforms in arid and semi-arid regions, whose mobility varies depending on climatic factors, especially the speed and frequency of erosive winds, rainfall, and the amount of evaporation and transpiration, which always causes many problems for the activity of these dunes. Therefore, monitoring climatic factors and analyzing dust events can be a positive step toward knowing the factors affecting their activity and predicting their mobility status in the future. Lut desert, with its huge amount of sand masses, is one of the most active places concerning changes in wind speed and direction. The eastern part of this region, which includes the largest sand mass of Iran, the Yalan sand, is dominated by the 120-day winds, which doubles the importance of investigating the winds and their shaping role during the blowing season of these winds. Based on this, the current research was conducted to analyze the mobility of quicksands in Lut plain stations in the past and predict their conditions in the future.

The study area includes the Lut desert located in Kerman province. To conduct this research, average monthly values of climatic elements including temperature, rainfall, hourly data related to horizontal field of view, wind speed and direction, and the code of various dust phenomena were used. These data were received from the Meteorological Organization of seven synoptic stations that have statistics for 20 years (2002 to 2021). Investigating the changes of climatic parameters over 20 years, investigating the temporal and spatial mechanism pattern of dust, wind and storm rose, calculating the amount of evaporation and transpiration using the Torrent-White method, investigating the condition of dunes using the Lancaster index were the main steps of the current research. The mobility of quicksands was texted using a sensitivity analysis and at the end, the zoning maps of the final sand transport potential were prepared using ArcGIS software.

The results showed that the stations leading to Lut plain are facing a decrease in rainfall and an increase in temperature, evaporation, and transpiration. The changes in wind speed are high in Shahdad station and low in Baft station, and the prevailing wind direction in most of the studied stations is west and north. The highest frequency of local and extra-local winds is related to Nehbandan station with 1090 days and Bam station with 791 days, and the lowest frequency of winds is Local and extra-local corresponding to Baft station with 23 and 31 days, respectively. The calculation of the aridity index of the stations showed that the index of prevailing climatic conditions in the region is dry, ultra-arid, and semi-arid due to the activeness of wind deposits and the peak time of local events in the stations located in plain areas, and this means Shahdad station has become a real desert in terms of desertification risk, Baft station is under severe desertification risk, and other five stations are under very severe desertification risk. With the reduction of the UNEP aridity index and the increase of the aridity of the environment, the amount of sand mobility in the whole Lut plain is increased and the risk of desertification in the region is intensified. Based on the sensitivity analysis, if in the future the frequency of winds exceeds the erosion threshold by 30%, the activity and movement of dunes will increase by 30%, while with a 30% increase in rainfall, the dune activity will decrease by 43%. Also, the sand mobility index has a positive relationship with changes in evaporation and transpiration. With a 30 % increase in evaporation and transpiration and the speed of erosive winds, the activity and movement of dunes increase by up to 70 %, and with a 30 % decrease in these two meteorological indicators, the activity and movement of dunes decrease by 50 %.

By calculating the Lancaster index, the potential activity of dunes has been determined and the active and inactive areas have been separated. The results of the zoning of this index showed that in the studied area, the activity level of dunes is mostly completely active and active at the top of the dunes. It is inactive only in Bam station, which has been done to stabilize and reduce dust activity and management measures such as planting trees, hand-planting desert forests, dunes, and mulching. However, due to the activity of the dunes in other stations, these measures are not enough and need new management and planning. The results of the present research can be used to predict the future condition of dunes and determine appropriate management measures to control and reduce possible damage to other land uses in the region.

Soil erosion is very obvious and noticeable in Iran, where a large part of it is a desert and the soil does not have a suitable cover. In order to reduce soil erosion and control it, it is necessary to identify factors affecting soil erosion. Land exploitation methods, forest and pasture exploitation, creation of residential and urban areas, geological conditions, precipitation, weather factors, etc. are some of the factors that affect the intensity of erosion in the region. Therefore, knowing the quantitative values of soil erosion is effective in accurately estimating the adverse, hidden, and intangible effects of erosion

In this research, the Revised Universal Soil Loss Equation (RUSLE) Model has been used. The amount of soil erosion in the basin was calculated in two 20-year periods (1980-2000 and 2000-2020). This soil erosion model is calculated through six factorsA=R×K×L×S×C×P      (R) the Rainfall erosivity factor, (k) soil erodibility factor, (LS) are slope length and slope degree factors respectively, (c) vegetation management factor, and (P) soil protection factor. The data in this research for the implementation of this model including the rainfall erosivity factor (R), topography including slope length and slope degree (LS), and vegetation management (C) were prepared from the Google Earth Engine system. The soil erodibility factor (K) was obtained from the natural resources report. The BLM model was also used to estimate the evaluation of the RUSLE model.  The Google Earth Engine system was used to prepare the land use maps of each of the 20-year periods. The land use map of the first period was prepared using the supervised classification method and calling Landsat 5 images, and The land use map of the second period was done using the CGLS-LC100 product, which is produced and updated at the Copernicus Global Earth Center and using Sentinel satellite images

By analyzing the obtained maps, the rain erosion factor for the first period (1980-2000) has an average of 2.02, the minimum value is 1.80 and the maximum is 2.29, and the second period (2000-2020) is from 1.55 to 2.07 is variable, its average is 1.783. The erodibility factor of the region's soils varies from 0 to 0.349 and its average value is 0.0264. The topography factor of the studied basin varies from 0 to 250 and its average value is 8.77. The vegetation management factor varies between 0.181 and 0.505 and its average is 0.353. This factor varies between 0.315 and 0.494 in the second period, and its average is 0.429 and has an increasing trend compared to the first period, which indicates the decrease of vegetation in the study area compared to the first period. The ground protection factor is also considered to be 1. To calculate the annual average soil erosion rate of the Award Basin in the first period (1980-2000), the various factors of the RUSLE model were converted to the same raster format and cell size, and coordinate system. To determine the risk of soil erosion, the produced layers including the rainfall erosivity layers, soil erodibility, topography, vegetation and soil protection factor were multiplied with the help of the Spatial Analyst extension of the ArcGIS program. The amount of annual loss of soil in terms of (tons per hectare per year) was obtained on a cell-by-cell basis. According to the results, the amount of erosion in the first period varies from 0 to 59.62 tons per hectare and its average is 1.64. The highest amount of soil erosion is in the middle and eastern regions with high slopes. In the second period, the layers of the soil erodibility factor, topography and soil protection factor are the same as in the first period because they are considered constant. The amount of erosion in the area in the second 20-year period varies from 0 to 63.38 tons per hectare, and its average is 1.75 and shows an increasing trend compared to the first period. The RMSE, MAE and MSE statistical indices were used to evaluate the accuracy of the RUSLE model and the degree of agreement of its erosion classes with the output of the BLM based on the map of sampling points. Examination of the values of the mentioned indicators showed that the root mean square error, mean absolute error and mean square error statistics in the RUSLE model have low values of 1.23, 0.96 and 1.52, respectively, as a result this model has It is a small error. After preparing the land use map for the first period, it was determined that in this period, the studied basin includes four land uses: forest, agriculture, pastures and woodlands, and residential. In the second period, there have been forest uses, destroyed forests, agriculture, pastures and woodlands, and residential areas. Then the land use maps prepared in the Google Earth Engine in two periods were transferred to the GIS environment system and the area of each of the above uses was obtained. The area of forests in the studied basin has decreased by 1590.956 hectares and 2014.827 hectares have been added to the area of degraded forests. Also, 2128/368 hectares have been added to the area of agriculture in this basin, and 2557/865 hectares have also decreased from the area of pastures in this area. It should be noted that 5.6266 hectares have been added to the area of residential areas of this basin.Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text. Click here and insert your abstract text.

The findings of this research in two 20-year periods (1980 2000) and (2000 2020) in the studied area show that the amount of precipitation in the second period has decreased compared to the first period. The amount of Rainfall erosivity in the first period had a minimum value of 1.80 and a maximum value of 2.29. In the second period, its value varied between 1.55 and 2.07. Thus, the amount of precipitation in the second period did not greatly affect the process of increasing soil erosion. However, the examination of the pictures and maps prepared on the amount of land use changes shows that the amount of forest and pasture area in this region has decreased and the area of destroyed forests and agricultural and residential lands has been added. Therefore, the role of land use changes in increasing soil erosion is significant. The research results of Teimouri (2018), Mayahi (2021) and Arkhi (2022) also confirm that increasing rainfall, changing land use and reducing vegetation are effective in increasing soil erosion.

Flood is one of the most common and widespread natural disasters that occur frequently around the world (Patra et al, 2016). In recent years, the damages and casualties caused by floods have been affected by various factors. However, increased population, land use change, and the development of residential areas are considered to be the boosters for the increase in damages. The decrease in the active width of rivers by different factors especially human interventions has increased the vulnerability facing floods. The damages are classified into tangible or intangible types. Tangible damages, including the destruction of buildings, agricultural lands, roads and transportation systems, infrastructures, environmental ecosystems, and human casualties impose a major negative emotional burden on the target society (Tiryaki and Karaca, 2018). Among the natural disasters, floods cause the most damage to the agriculture, fisheries, housing, and infrastructure sectors and severely affect economic and social activities. Despite the natural cause of the floods in Iran, the main cause of the damages may be due to the human settlement in the high-risk areas (Mustafa et al, 2018, Nga et al, 2018). In recent years, about 70% of the annual budget dedicated to decreasing natural disasters have been allocated to recovering the damages by flood and this trend is increasing, so the 250% growth of flood damages in the last five decades confirms this claim (Demir and Kisi, 2016).

This applied quantitative research was carried out in the Cheshme kile river, located in Tonekabon City in 2021-2022. In the first stage, indicators affecting flood vulnerability were prepared using the study of the research background. In this regard, the data of 6 indicators of aging ratio, sex ratio, youth ratio, land use, population density, structure quality, and material quality were prepared as effective indicators of flood vulnerability. Data were collected using the statistical yearbooks by referring to the National Statistics Center of Iran, which was recorded in the last census in 2016. In the next step, the relationships defined according to Table 1 were used to prepare each index. Zoning the floodplain area is applicable to detect the vulnerable area. The map of floodplain zoning is the result of modeling based on the HEC-RAS model (Saffari et al, 2023). The data of each of the indicators was overplayed with the layer of urban blocks of Tonekabon using ArcGIS 10.3 software. Then, the Vikor method was used to prepare flood vulnerability zoning maps. The data normalization was carried out due to the different data spectrums. Then, the weight of each index and sub-index was prepared using the AHP method. After determining the weight of each index, positive and negative ideals were determined. Positive ideals are the highest values of each index and negative ideals are the lowest values of each index. The result of subtracting the positive ideal from other sub-indices is the index of usefulness, and the result of subtracting the negative ideal from each of the sub-indices is the regret index (Table 2). The regret and usefulness indicators were classified (very high, high, medium, low, and very low) for each of the layers using the reclassify tool through ArcGIS software. (Figures 2 and 3). The classification spectrum for each of the layers is presented in Table 2. After calculating the indices of usefulness and regret, a flood vulnerability map was prepared for the study area using Equation 5 (Figure 3). In this map, values close to zero show the highest vulnerable area, and values close to one show the lowest vulnerable area conditions. To better understand the distribution of risk zones, the target map was classified into 5 spectrums of very high risk, high risk, medium risk, low risk, and very low. According to the findings, the area of risk zones in very high, high, medium, low, and very low classes were 0.36, 0.26, 0.34, 0.28, and 0.19 kilometers, respectively. The largest and lowest area of risk zones were observed in the very high and very low classes.

The aim of this study was to investigate the vulnerability of the Cheshme Kile River in the area of Tonekabon City facing floods using the Vikor multi-criteria decision-making method based on the geographic information system (GIS). Effective criteria in flood vulnerability included land use, population density, youth ratio, aging ratio, gender ratio, and quality of structures and materials. The findings show the low vulnerability facing floods in the southern areas on the left side and the northern areas on the left and right sides of the Cheshme kile river due to the low population density, the low active width of the river channel, and the presence of green spaces. On the other hand, the density of the population and the dense building texture on the left banks in the western and northwestern margins have led to a decrease in soil permeability levels and an increase in the volume of urban runoff. Therefore, these areas are more vulnerable to floods and urban runoff. According to the findings, the highest and lowest areas were observed at very high risk and very low zones.
The width channel of the river has increased downstream, while the slope of the river has decreased, which increases the water level and the possibility of financial and human losses. As can be seen in Figure 4, areas with high vulnerability can be seen on the left and right banks in the downstream section of the river.  In these layers, factors such as population density at the range of 192-67 and 192-408, youth ratio in the ranges of 19.21-26-43 and 14.19-21, structure quality in the very unfavorable range, the aging ratio in the range 9-18, the gender ratio in the range of 27.56-44.74 and building and industrial lands have increased the risk of flood vulnerability in this area. Naturally, by reducing the range of investigated indicators, the risk of flood vulnerability also decreases. For example, in a factor such as the youth ratio, the lower the relative spectrum, the greater the risk of flood damage.

Considering the high costs of controlling wind erosion and the difficulty of working conditions, choosing basic and technical methods to stabilize these areas, in addition to increasing work efficiency, will also be effective in reducing costs. The first priority and the most effective method of controlling wind erosion is to cover the ground with vegetation, and the more the amount of vegetation, the more effective its role will be. If it is not possible to implement biological plans, mechanical and chemical methods such as mulching should be used. Usually, the main purpose of using mulch in quicksand stabilization activities is to increase the stability of the soil surface against wind erosion in order to create a period during which there is a suitable opportunity to carry out and establish other biological activities of sand stabilization such as planting, sowing seeds, cuttings, etc., and these biological materials can be established in the desired field. In this regard, this research was carried out with the main purpose of investigating the effect of two combined mulches, Pistachio-PAM and Pistachio-PVAC, on the growth and development and nutrition of the Haloxylon persicum.

Pistachio-PAM and Pistachio-PVAC mulches are new hybrid mulches that combine an optimal ratio of pistachio harvest residues and polyacrylamide (PAM) and polyvinyl acetate (PVAc) water-soluble polymers extracted from these wastes and water has been obtained. In this study, the establishment, growth and development of the Haloxylon plant under the conditions of applying Pistachio-PAM and Pistachio-PVAC mulches and the conditions without mulch spraying (control sample) were investigated in four replications. The effect of treatments on the growth and development of Haloxylon was determined after a period of 4 months and afterward, the plants were cut from the crown and the shoot and root parts were separated. Then, shoot and root dry weights were determined and the concentrations of nitrogen, phosphorus, potassium, iron, zinc, copper, and manganese in roots and shoots of the plants were measured separately. Finally, statistical analysis was performed using Minitab 14 software in the form of a completely random design, and the average repetitions were compared with MSTATC software in the form of Duncan's multi-range test.

The results showed that utilization of both mulches caused a significant increase in the shoot and root dry weights and also nutrient concentrations and their absorption by the plants. Furthermore, the presence of the investigated mulches increased significantly the root concentration of elements such as nitrogen, potassium, and manganese, where an increase of almost 250 % in the potassium concentration was observed. Also, both mulch treatments increased significantly the shoot dry weight, N and K concentrations in Haloxylon shoots and an increase of almost 150 % in the shoot dry weight was achieved in the plants treated with the mulch compared to the control.

The increase in vegetative growth in plants and the consequent increase in the concentration and absorption of elements in plants can be discussed in several aspects. Preventing the evaporation of water in windy sand is one of the factors that can be effective in increasing the vegetative and nutritional characteristics of the plant. The presence of a layer with large pores filled with air on the surface of the soil can act as thermal insulation and prevent the transfer of heat to the bottom layers of the pot and water evaporation. The use of two combined mulches, Pistachio-PAM and Pistachio-PVAC, had an effective role in plant water relations, vegetative growth, and improving the nutrition of the plant. Considering that, in order to increase the effectiveness of mulching areas sensitive to erosion or fine dust production, resistant plants suitable for biological control are usually cultivated. Therefore, it seems that the use of Pistachio-PAM and Pistachio-PVAC mulches can play an effective role in improving the growth of Haloxylon plants and it is possible to use the mulching-crown cultivation system in sand fields to stabilize flowing sands, control wind erosion and produce fine dust.

Reducing the capacity of preservation of water and nutrients, poor soil aggregation, instability of soil structure, reducing the rate of water infiltration into the soil, reducing microbial activity, reducing soil fertility and consequently reducing growth and yield of plants are the common problems of saline-sodic soils. Among of the agricultural soil amendment which can enhance agricultural productivity and soil sustainability, one that is organic in nature, is biochar. Biochar is the product of pyrolysis of many types of organic materials in the absence or partial absence of oxygen and at high temperature (usually around 450 degrees Celsius). More recent studies have reported positive improvements from the incorporation of biochar into poor soils, including decreased bulk density, increased water holding capacity, liming effect, and enhanced nutrient availability; but it depends on the type of feedstock’s and production conditions of the biochars. Due to the fact that in our country, the area of saline-sodic soils is very large (10-15% of the country's area) and a little research has been done about the effect of usage of various types of organic modifiers on the improvement of saline-sodic soils properties, consequently, this study aimed to investigate the effects of adding some of organic modifiers, which most of them were organic wastes, on some physical and chemical properties and to improve saline-sodic soil.

This study was carried out in a saline-sodic soil as a pot experiment in a completely randomized design with 13 treatments and 3 replications in the greenhouse conditions at the University of Jiroft. Treatments including 6 types of organic modifiers (wheat straw, palm waste, vermicompost, cocopeat, wheat straw biochar and palm wastes biochar) that each one was considered at two levels (5 and 10%) with control. The organic modifiers were later grounded and sieved with 2 mm sieve and made ready for application. The treatments were added to saline-sodic soil and incubated for 90 days by maintaining moisture content at the moisture of the field capacity of soil (it was done by weighing the pots). After incubation period, some chemical and physical properties of soil including pH, salinity (EC), sodium adsorption ratio (SAR), bulk density and clay dispersion were measured. Also, some biological properties including soil microbial respiration and alkaline phosphatase activity were measured.  Data collected from each experiment were subjected to analysis using SAS Ver.9.4. The differences between mean values were identified using Duncan’s multiple range tests at a significance of p< 0.01.

The results indicated that adding organic modifiers caused significant changes in physical, chemical and biological soil properties.  Addition of organic modifiers to the soil caused a significant decrease in pH and SAR compared to control pots. All organic modifiers greatly increased soil microbial respiration, alkaline phosphatase activity and EC in compared to the control and organic modifiers addition at a higher level finally resulted in a higher value of soil EC. Application of organic modifiers soil reduced clay dispersion of the soil compared with the control. For example, clay dispersion was significantly reduced about 52 and 54 percent in compared to the control, by adding 10% of wheat straw and palm waste, respectively. Other organic modifiers had less effect on reducing clay dispersion than wheat straw and palm waste, but effect of all treatments on this parameter were significant in compared to the control. Also, the results of this study showed that addition of all organic modifiers to the soil, decreased soil bulk density compared to control which maximum decreasing was observed by application 10% of cocopeat and wheat straw biochar. Biochar has high porosity which results from retaining the cell wall structure of the biomass feedstock. Therefore, being a porous material when added to the soil, it increases its porosity and thus reduced bulk density.

According to the results, cocopeat particularly at 10% level application, had highest effect on soil properties and to improve of saline - sodic soils. Generally, the use of organic materials in poor soils could increase the soil organic matter therefore improves its physical and chemical properties of soil, especially when the soil has additional problems from destructive factors such as salinity and sodicity. In addition, organic modifiers production has caused the optimal use of agricultural and industrial wastes and can be used to protect the environment and reduce pollutants. Also, the use of these wastes as biochar could be a more environmentally friendly solution. However, further researches are needed to determine the impacts of a specific biochar on a specific saline- sodic soil.

Land subsidence, as one of the environmental hazards, is happening in many countries of the world. This phenomenon, if not properly managed, can cause irreparable damage. In this regard, Iran, as one of the countries that has been facing the risk of land subsidence for several decades, will probably be affected by the damage of this phenomenon in the near future. Damages including; Damage to agricultural lands, buildings, roads, bridges, pipelines, etc. Various activities such as; Mining, excessive extraction of underground water, etc., have intensified the process of land subsidence to the point where it has become one of the most important hazards of geomorphology. Identifying the boundaries, the pattern of land subsidence and estimating its intensity will play a significant role in the management and control of this phenomenon. Therefore, it is necessary to take measures to prevent further problems. Therefore, the important goal of this research is to evaluate the subsidence of the Kashmer plain with the radar interferometry method and its relationship with the groundwater drought. Maybe the results of this research can help the executive managers and planners of land and soil resources in the field of protection and management of water resources to prevent land degradation.

In this research, radar interferometry was used to monitor subsidence, and Kendall and Pettit's time series analysis tests were used to evaluate groundwater drought. Also, to calculate the density of wells, kernel density estimation was used, which transforms and determines the position of points in space in a continuous density function in the studied area. Finally, to determine the correlation coefficient and covariance between the existing rasters, as well as some statistical parameters such as the minimum, maximum, average and standard deviation values for each raster, Band Collection Statistic analyzer, which is considered a part of multi variate analyzers was used. Two SENTINEL satellite images were used to determine the amount of subsidence in the target area: 1- The Master image was taken on 04/04/2017. The variable image of 03/25/2021 Slav was also used with a time span of about 4 years and using Land subsidence was calculated from SNAP software. The PSI index was used to determine the level of groundwater drought. This index can be used for all piezometric levels.

The results of the radar interferometric analysis showed that the subsidence in the studied area was due to excessive water withdrawal from wells and underground water sources. The cause of subsidence around the wells was due to the lack of equipment and the entry of particles into the well. The results of changes in the time series of the PSI index showed that it is insignificant at the probability level of 5% in Kalate Rahim and Khalil Abad wells and significant in the rest of the wells. In the studied area, the lowest water level drop is related to the wells of Khalil Abad, Kalate Rahim. Khalil Abad well has had a drop in water level from 1996 to 2006, and from 2006 to 2021, the PSI index had an upward trend. The analysis of PSI data up to 2019 showed that the groundwater drought in the Kashmir plain has reached its peak over time, and from 2019 to 2014, the conditions have somewhat returned to normal conditions. In addition, subsidence is developing from the western areas such as Khalilabad, which have been involved in this issue in the past, towards the central areas and the center of Kashmar plain. The highest density of wells in the study area is in the central areas towards the western areas of the plain.The study of the land use map of the region also showed that the majority of the density of wells is related to agriculture and irrigated agriculture, which includes 76% of the exploited wells.

The obtained results showed that in different regions of Kashmir Plain, in the period of 4 years (2017 to 2021), there was about 46 to 84 cm of land subsidence, which means that annually in different areas between 11.5 and 21 cm of subsidence can be observed. On the other hand, the process of subsidence has reached the central areas from the west of the Kashmar plain, and the highest intensity of subsidence can be seen around the city of Kashmar. The time series of PSI groundwater drought index is insignificant in Kalate Rahim and Khalil Abad wells and significant in the rest of the wells. Regarding the relationship between the amount of land subsidence and the severity of groundwater drought, the highest amount of subsidence is located in the areas that are in the minimum historical conditions of the PSI index and include the highest fluctuation of subsidence in the region. As we approach the normal conditions of the region in terms of the PSI index, the amount of subsidence also decreases, which indicates a strong connection between groundwater drought and land subsidence. The future perspective of the dangers caused by this phenomenon is very difficult and even impossible, considering the vast dimensions of the damage it causes to the fields of natural resources. Therefore, the custodian bodies, including the country's natural resources and watershed management organization, the General Directorate of Natural Resources and Watershed Management, the Jihad Agriculture Organization, the Regional Water Company of Khorasan Razavi Province, have a very heavy responsibility in managing the crisis and improving the conditions.

Wind erosion is one of the destructive phenomena that cause environmental changes, changes in the quality of the weather threatens public health, and other economic and social issues in regions with dry and semi-dry climates. Using wind tunnels, the effect of wind velocity and soil properties, as well as the particle transport process, can be investigated under controlled conditions. Ries and Fister estimated the amount of wind erosion in the Ebro basin using a portable wind tunnel in 2009. To evaluate the rate of soil loss, three sample locations were assessed, and the results showed that the areas with unchanged ground surface had the lowest amount of wind erosion. The phenomenon of dust storms in Khuzestan province has had an increasing trend in terms of frequency and continuity in recent years. Considering the issue's importance, the present study was conducted to determine the threshold erosion velocity and erodibility of soils taken from the dust storm centers of Mahshahr, Omidiyeh, and Hendijan, using a wind erosion measurement device.

The dust centers of Mahshahr-Omidiyeh-Hendijan are located between 30°12'28" to 30°50'57" north latitude and 48°47'45" to 49°41'41" east longitude and have expanded between Mahshahr and Omidiyeh and Hendijan. Using the land unit map, maps from the Geological Survey Organization, and field studies, 32 points were identified in the Mahshahr, Omidiyeh, and Hendijan centers, representing various land units differentiated in the soil map. Finally, ten average points were selected. Samples taken from the soil surface inside the wind tunnel were tested. First wind thereshold velocity, Then the wind erosion rate was measured at speeds of 15, 20, 25, and 30 (m/s) for two minutes, and finally, the wind erosion rate of the sample points was obtained. The median diameter and mean diameter of the particles were determined using Gradistat software to determine the erodibility of the sample particles according to the Chepil theory (Table 2).

 the amount of wind erosion increases at wind speeds of 15, 20, 25, and 30 (m/s) over two minutes. Under these conditions, higher wind speeds intensify soil loss and lead to an increase in the rate of wind erosion. The wind erosion threshold varies from 6 to 17 (m/s). The minimum wind threshold velocity is related to the Jarahi-Mahshahr sedimentary plain, which is sensitive to wind erosion at a threshold speed of 6 meters per second and the total amount of wind erosion rate of 12160 (gr/m2.min). The total amount of erosion rate ranged from 360 to 21860 (gr/m2.min) and the highest erosion rate was related to alluviums and alluvial cones in the shape of the Hendijan anticline. the erosion potential of soils taken from dust centers in Khuzestan province is high, and the dominant particle diameter of the soil is 0.5-0.15 (mm) and 0.05-0.1 (mm), which are susceptible to wind erosion. Therefore, all samples collected from dust centers in Khuzestan province are sensitive to wind erosion

   Locating areas sensitive to wind erosion is one of the important solutions for stabilization. Given the importance of the issue, this study has focused on estimating the erosion potential and threshold velocity in the dust centers of Mahshahr, Omidiyeh, and Hendijan. The results of measuring the erosion rate using a wind tunnel device showed that the soil in these areas has a high erosion potential, and the erosion rate increases significantly with increasing wind speed. The minimum of the wind threshold velocity for sedimentary plains in jarahi-Mahshahr region, located in the northwest center, which indicates the high sensitivity of the soil in the area to wind erosion. The highest amount of wind erosion rate was related to alluvial fans and alluvial cone in the shape of the Hendijan anticlin. The fan-shaped alluviums deposited by the temporary rivers at the foot of the anticline mountains east of Hendijan, because the materials transported by the temporary rivers are mostly fine-grained and marls, so the amount of gravel in these alluviums is low and for this reason, the erosion susceptibility of these soils is very high and they should be stabilized in the early stages. These results are consistent with the results of Abbasi, which led to the preparation of a map of land sensitivity to wind erosion in this center. Studies related to particle size distribution showed the high sensitivity of the samples to wind erosion. Since the dominant diameter of all particles in the samples was in the range of 0.5-0.15 and 0.1-0.05 (mm), the potential for erosion susceptibility of all samples in the study area is high. However, in this theory, only one factor has been used to determine the potential for soil erosion and other effective parameters in erosion susceptibility have not been considered, so it is not possible to rely solely on this theory to estimate erosion.