Showing 69 results for Erosion
N. Hasanzadeh, L. Gholami, A. Khaledi Darvishan, H. Yonesi,
Volume 25, Issue 1 (5-2021)
Abstract
Soil erosion is one of the most serious environmental issues in the world, causing soil degradation, reduction of land productivity, increasing flood, water pollution and pollutions transportation; it is also a serious threat to sustainable development in the world. Therefore, the soil conservation and the prevention of soil erosion and use of conditioners as the nanoclay can be considered as a solution to improve land productivity and protect environment. The present study was, therefore, conducted to address the effect of the application of montmorillonite nanoclay with three rates of 0.03, 0.06 and 0.09 t ha-1 on changing runoff and soil loss variables under laboratory conditions. The results showed that the nanoclay with the rate of 0.03 t ha-1 could decrease the runoff coefficient, soil loss and sediment concentration with the rate of 40.65, 88.38 and 82.19 percent, respectively. The average of soil loss in control treatment and conservation treatments of nanoclay with various rates was measured to be 3.76, 0.44, 1.33 and 3.16 g, respectively. Also, the results showed that the most sediment concentration was the control treatment with the rate of 5.84 g l-1 and the conservation treatments with nanoclay in the applied rates was 1.04, 3.47 and 2.96 g l-1, respectively. Also, the results showed that the nanoclay effect was significant on changing the soil loss and sediment concentration at the level of 99 percent. Finally, due to the effect, the use of this conditioner in natural conditions and investigation of the effects on environment and aggregates stability are recommended.
J. Chezgi, M. Asiyaei,
Volume 25, Issue 1 (5-2021)
Abstract
Erosion causes the reduction and degradation and the soil fertility; one of its most important consequences, endangering the food security of the inhabitants of the area. Therefore, to reduce erosion, it needs to be controlled and managed using good soil conservation methods. It is only necessary to manage and control the full impact of the factors affecting the soil first. If there is a critical state of erosion in the four watersheds, identifying the precise location of erosion will be done quickly and with less cost; thus, further erosion control and counter-operation will be feasible. In this study, geographic information system and decision making models of AHP and ANP in Bagheran region of Birjand were used to determine the erosion prone areas. First, 10 effective criteria including rain, slope, slope direction, soil, geology, permeability, vegetation, land use, distance from road and village, were determined on the erosion in the area based on the expert opinion and library studies. Next, the questionnaires were sent to experts to explore g the impact of the criteria on erosion; after completing the questionnaires based on Expert Choice and Supper Decision software, the relative importance of the criteria was obtained. The maps were then compiled and integrated according to the relative importance of the criteria. Rainfall factor had the greatest impact on the erodibility of the area in the AHP method with the relative importance of 0.21 and the vegetation criterion with the weight of 0.158 in the ANP method had the most impact on the determination of erosion prone areas. Finally, the erodibility map of the area was obtained based on the presented models. Subsequently, the region was classified into five classes of erosion susceptibility, with areas of moderate sensitivity having the most area in both models. In the lower and upper classes, the ANP method performed better; in the middle classes the AHP method performed better.
F.z. Asadi, R. Fazloula, A. Emadi,
Volume 25, Issue 3 (12-2021)
Abstract
Investigating and understanding river change issues is one of the important factors in sediment hydraulic sciences and river engineering. These studies can be done with the help of physical, mathematical models, or both, but due to financial and time constraints, mathematical models are more general and often used. In this study, the GSTARS model was used to investigate erosion and sedimentation and select the most appropriate function in 12.5 km in length from the Talar river in Mazandaran Province. Simulation using the 55 sections taken in 2006, the daily flow data of the hydrometric station of the Shirgah, located at the beginning of the rich and characteristics of the river sediment, was done. The calibration and validation of the model with cross sections taken in 2012 showed that Yang's sediment transport equation has the highest correlation with reality and can be used to predict river change. The amount of sediment depleted from the case study using the Yang equation is estimated at 8590 tons per year. Also, the study of longitudinal profiles of the river with different sediment transfer functions showed that the study reach at the end range has an erosion trend and is not capable of sand and gravel mining.
L. Gholami, A. Khaledi Darvisan, N. Karimi,
Volume 25, Issue 3 (12-2021)
Abstract
Soil loss can cause many intra-regional and extra-regional problems, on the other hand, the effect of soil moisture on processes of soil loss and sediment yield for the identification and simulation of soil hydrological response is necessary. Therefore, the application of soil conditioners is essential for soil and water conservation. The present study was conducted to investigate the effect of soil conditioners of vermicompost and nano-manure on variables of soil loss and sediment concentration at moistures of air-dried, 15 and 30%, and rainfall intensities of 50 and 90 mm h-1. The obtained results in addition to confirmation of the significant effect of each conservation treatment at the level of 99 percent on the intended components showed that the conservation treatment of vermicompost compared to nano-manure treatment had more effect on measured variables. Also, the conservation treatment of vermicompost could decrease the soil loss at soil moisture air-dried, 15, and 30 percent with rates of 72.15, 66.63, and 78.76 percent (50 mm h-1), respectively, and 45.01, 35.57, and 10.45 percent (of 90 mm h-1), respectively. The effect of conservation treatments, soil moistures, and rainfall intensity and the interaction effects of conservation treatments × rainfall intensity and rainfall intensity × soil moisture on changes of soil loss and sediment concentration were significant at the level of 99 percent. The application of vermicompost and nano-manure had acceptable results on studied parameters but the vermicompost effect was more than nano-manure. Therefore, due to the widespread use of different types of conditioners, nowadays, it is needed to move the application feasibility of conditioners such as vermicompost and nano-manure that these have not the adverse effects of environmental.
A.r Modares Nia, M. Mirmohamad Sadeghi, A. Jalalian,
Volume 25, Issue 4 (12-2021)
Abstract
Desertification has become one of the main problems of human societies living in the vicinity of desert areas in recent years. One of the methods that have been considered in recent years and are rapidly expanding in the field of soil mechanics is the Microbial Induced Carbonate Precipitation (MICP). In this method, urea-positive organisms that are naturally present in the soil can stabilize the soil and improve its engineering parameters by using urea and calcium chloride. Recently, attempts have been made to use this method to create a crustal layer on the soil to prevent wind erosion. In the present study, the effect of environmental conditions in deserts such as temperature and sand bombardment on microbial soil treatment has been investigated using this new method. The soil of the Segzi region as one of the main centers of dust in the Isfahan region was studied in this research. Therefore, the improved samples are subjected to regional temperatures which increased the surface layer resistance with increasing temperature. Also, the sandstorm conditions of the region were simulated using three different grain sizes of sand inside the wind tunnel. The results of these experiments showed that stabilized soil could withstand the conditions at wind speeds of 7 and 11 m/s. However, by increasing the wind speed to 14 m/s and the grain size, the crustal layer destroys and increases the wind erosion of the soil. Also, the resistance of the surface layer increased by increasing temperature in the tested samples. This increase in resistance continued up to 24 degrees with a high slope, but from 24 degrees onwards, this slope decreases. Based on the results of this research, it can be said that the microbial improvement method can be used as an alternative method in the future to stabilize desert soils.
S. Dehghan Farsi, R. Jafari, A.r. Mousavi,
Volume 26, Issue 2 (9-2022)
Abstract
The objective of the present study was to investigate the performance of some of the extracted information for mapping land degradation using remote sensing and field data in Fras province. Maps of vegetation cover, net primary production, land use, surface slope, water erosion, and surface runoff indicators were extracted from MOD13A3, MOD17A3, Landsat TM, SRTM, ICONA model, and SCS model, respectively. The rain use efficiency index was obtained from the net primary production and rainfall map, which was calculated from meteorological stations. The final land degradation map was prepared by integrating all the mentioned indicators using the weighted overlay method. According to the ICONA model, 5.1, 9, 47.21, 27.91, and 10.73 percent of the study area were classified as very low, low, moderate, severe, and very severe water erosion; respectively. Overlaying the ICONA map with other indicators showed that very high and high classes, moderate, and low and very low classes of land degradation covered 1.3, 18.7, 70, 0.9, and 9.1 percent of the study area, respectively. According to the results, integrating remote sensing with ICONA and SCS models increases the ability to identify land degradation.
P. Fattah, Kh. Hosseini, A.a. Hashemi,
Volume 26, Issue 3 (12-2022)
Abstract
Splash (raindrop) erosion plays an significant role in soil loss, especially in arid and semi-arid regions with poor vegetation. In this paper, by analyzing the pattern of rainfalls that occurred during 26 years in four basins located in Semnan County, their effect on the pattern of eroded sediments from the basin was investigated. Sedimentary layers from the sampling of retarding reservoir sediments in 2017 were related to the corresponding precipitations. Due to the occurrence of the highest amount of rainfall in each quarter of rainfall, rainfall hyetographs were divided into four categories. Cumulative precipitation curves with similar quartiles were drawn in one shape and compared with sediment curves and vice versa taking into account the physical characteristics of the basin. The results showed that the Aliabad basin (with less slope and more elongation) with an effective quarter of type 3 had the highest similarity in precipitation and sediment patterns. Also, the Western Soldereh basin (with the highest slope and the least elongation) with an effective quarter of type 2 had the least similarity in precipitation and sediment patterns. The results indicate the vital role of rainfall patterns on the resulting sediment patterns, which show up to 85% similarity.
B. Shahinejad, A. Parsaei, A. Haghizadeh, A. Arshia, Z. Shamsi,
Volume 26, Issue 3 (12-2022)
Abstract
In this research, soft computational models including multiple adaptive spline regression model (MARS) and data group classification model (GMDH) were used to estimate the geometric dimensions of stable alluvial channels including channel surface width (w), flow depth (h), and longitudinal slope (S) and the results of the developed models were compared with the multilayer neural network (MLP) model. To develop the models, the flow rate parameters (Q), the average particle size in the floor and body (d50) as well as the shear stress (t) as input and the parameters of water surface width (w), flow depth (h), and longitudinal slope (S) were used as output parameters. Soft computing models were developed in two scenarios based on raw parameters and dimensionless form independent and dependent parameters. The results showed that the statistical characteristics in estimating w, the best performance is related to the MARS model, whose statistical indicators of accuracy in the training stage are R2 = 0.902, RMSE=1.666 and in the test phase is R2 = 0.844, RMSE=2.317. In estimating the channel depth, the performance of both GMDH and MARS models is approximately equal, both of which were developed based on the dimensionless form of flow rate as the input variable. The statistical indicators of both models in the training stage are R2 » 0.90, RMSE » 8.15 and in the test phase is R2 » 0.90, RMSE = 7.40. The best performance of the developed models in estimating the longitudinal slope of the channel was related to both MARS and GMDH models, although, in part, the accuracy of the GMDH model with statistical indicators R2 = 0.942, RMSE = 0.0011 in the training phase and R2 = 0.925, RMSE = 0.0014 in the experimental stage is more than the MARS model.
Mrs Soghra Bagheri, M.r. Ansari, A. Norouzi,
Volume 26, Issue 3 (12-2022)
Abstract
Soil erosion has been one of the most important problems of watersheds in the world and is considered one of the main obstacles to achieving sustainable development in agriculture and natural resources. Identifying and prioritizing regions sensitive to soil erosion is essential for water and soil conservation and natural resource management in watersheds. The present research was performed in 2021 year to prioritize the soil erosion susceptibility in 12 sub-watersheds of the Roudzard watershed in Khouzestan province using morphometric analysis and multiple criteria decision-making (MCDM) methods. In this regard, 11 morphometric parameters including shape parameters such as compactness constant (Cc), circularity ratio (Rc), form factor (Rf), elongation ratio (Re), linear parameters such as drainage density (Dd), stream frequency (Fs), drainage texture (Dt), bifurcation ratio (Rb), Basin length (L), Length of overland flow (Lg), and topographic parameter including Ruggedness number (Rn) were extracted and their relative weights were calculated using Analytic Hierarchy Process (AHP). The prioritization sub-watershed to soil erosion was performed using TOPSIS, VIKOR, and SAW methods, and the results were combined using rank mean, Copeland, and Borda methods. The final prioritization was compared with the amount of specific erosion in the MPSIAC model by determining Spearman's correlation coefficient. The result of the evaluation of morphometric parameters by using the AHP model showed that drainage density (0.161), drainage texture (0.158), and stream frequency (0.146) had the greatest effect on the erodability of the sub-watersheds. In contrast, the form factor (0.049), Elongation Ratio (0.036), and shape factor (0.026) had the least effects on erodability of the study area. In this research, the Spearman correlation coefficient between the final result of prioritizing the sub-watershed and the MPSIAC model was obtained as 0.8 in p-value<0.01. The results of prioritization of the sub-watersheds in terms of their sensitivity to soil erosion showed that sub-watersheds 11, 12, and 10 with an area of 191.83 km2 are categorized as very sensitive to soil erosion due to high value of linear parameters, low value of shape parameters, sensitive geology formation, and poor vegetation cover and located in rank 1 to 3, respectively. According to the results sub-watersheds 11, 12, and 10 have the highest amount of specific erosion equal to 16.03, 12.48, and 11.6 tons per hectare per year, respectively. Therefore, these sub-watersheds are a priority for watershed management operations. The results of the present study showed that MCDM methods and morphometric analysis are suitable tools for identifying areas sensitive to soil erosion and using the combined methods of the results and it is possible to take advantage of each of the different multi-criteria decision-making methods.
E. Javiz, A. Jalalian, M.r. Mosaddeghi, E. Chavoshi, N. Honarjoo,
Volume 26, Issue 4 (12-2022)
Abstract
One of the most significant environmental crises in arid, semi-arid, sub-humid, and even humid regions is the destructive phenomenon of desertification and in the arid and semi-arid regions is wind erosion. These problems exist in large areas of Iran and it is necessary to use an environmentally friendly and economic method to solve this problem. In this study, calcium bentonite clay was used for the first time in Iran and perhaps in the worlds in the critical region of Sajzi, which covers an area of 65 hectares. Experiments were performed on the crusts after one year of mulching with bentonite clay. The results showed that wind erosion has a negative and significant correlation with the mean weight diameter and geometric weight diameter of aggregate, aggregates with diameters greater than 0.25 mm, shear strength, and penetration resistance. On the other hand, the results of the permeability test using double-ring and by three models (Kostiakov, Horton, and Philip) showed that the lowest mean square error (SSE) and the highest coefficient of determination (R2) belonged to the Kostiakov model in the mulch-applied and control samples. This result indicated the superiority of the Kostiakov model compared to Horton and Philip's models. Wind erosion intensity was also measured in situ using a portable wind tunnel at 20 points in the Sajzi region. The findings showed that mulch application has controlled more than 95% of soil erosion.
Z. Nazari, M. Moeinaddini, S. Zare, R. Rafiee,
Volume 27, Issue 1 (5-2023)
Abstract
Due to the environmental problems caused by wind erosion, it is necessary to stabilize the dust centers with mulches. The objective of the present study was to determine and compare the optimum vinasse mulches based on mechanical indicators for sensitive soil stabilization to wind erosion. In this research, vinasse (0, 100, 200 g) is combined with bagasse (0, 25, 50 g), ash bagasse (0, 25, 50 g), filtercake (0, 12.5, 25 g), and one-liter water (81 treatments). At first, the treatments were determined in the appropriate range of salinity and acidity (35 treatments) and in the next step, the mechanical indicators have been measured after mulching on laboratory trays (2×30×100 cm). Optimum mulches have been determined based on five indicators by mean comparison (Duncan). The mean comparison showed that treatments 33, 30, 34, 32, and 19 show the mean difference between the groups based on layer thickness, impact resistance, compressive strength, and shear strength properly. It can be concluded that vinasse (100 and 200 g) with 50 g bagasse reduces the crack coefficient greatly, and the application of vinasse, bagasse, and filtercake does not affect the compressive strength and impact resistance.
D. Khatibi Roudbarsara, A. Khaledi Darvishan, J. Alavi,
Volume 27, Issue 2 (9-2023)
Abstract
Soil erosion followed by sediment production is the most important phenomenon that causes soil and environment degradation in many areas and is increasing. Sediment fingerprinting is a method to identify sediment sources and determine the contribution of each source to sediment production. The present research was carried out to evaluate the relative erosion sensitivity of lithological units and to determine the contribution of each unit in bed sediment production using geochemical properties in the Vaz River located in Mazandaran province. The 33 soil samples were taken from the whole watershed and one sediment sample at the outlet of the watershed. Then, five tracers of B, Al, Sc, Mo, and Sn were selected as the optimal combination using three statistical tests range tests, Kruskal-Wallis, and discriminant function analysis. Finally, using optimal tracers and a combined multivariate model, the contribution of lithological units with very high (A), high (B), medium to high (C), and medium (D) sensitivity in bed sediment production were obtained using FingerPro statistical package and R software. The results showed that the contribution of lithological units with very high (A), high (B), medium to high (C), and medium (D) sensitivity in bed sediment production were 24.23, 50.77, 15.62, and 9.36%, respectively. Then, the specific contribution of each sensitivity class was also calculated to remove the effect of area on the results. The Qal lithological unit including the Quaternary sediments in the river bed and banks with very high sensitivity to erosion (A) and a specific contribution of 0.0807 % per hectare had the maximum contribution in bed sediment production in Vaz River.
S. Esmailian, M. Pajouhesh, N. Gharahi, Kh. Abdollahi,
Volume 27, Issue 3 (12-2023)
Abstract
Awareness of the number of changes in runoff and sediment on different slopes can be useful in modeling the production of runoff and sediment. Therefore, this study was conducted to investigate the production of surface and tunnel runoff and sediment in saline and sodic soils on different slopes. Saline-sodic soil was collected and transported to the laboratory. Laboratory experiments were performed on a soil bed in a rectangular flume at three different slopes (5%, 10%, and 15%) under simulated rain (30 mm/h) for one hour. An analysis of variance was used to investigate the effect of slope on runoff and sediment production, and the means were compared using Duncan's test at the five percent level using SPSS version 26 software. The results showed that there was a significant difference between the slopes of the runoff (P<0.001) and sediment (P<0.001). In the first minute of the experiments, due to the lack of moisture in the soil, the amount of runoff was low, but over time, the amount of runoff increased. It is because the pores are blocked by the dispersion of soil particles owing to the presence of sodium ions, which ultimately leads to a decrease in permeability. Similarly, in the last few minutes, outflow from the tunnel was observed, and this flow occurred only on slopes of 10% and 15%. The amount of sediment was also low in the first few minutes, which could be related to the low amount of runoff and the lack of sediment particle removal. Nonetheless, after the lapse of time, its amount increased, and the primary reasons were reduced permeability, increased runoff, and removal of fine particles from the soil surface.
M. Abtahi, M. Khosroshahi,
Volume 27, Issue 4 (12-2023)
Abstract
Biological operations to combat wind erosion must be carried out in the calm bed of dunes, which is often challenging due to high-velocity winds. Therefore, the necessary precondition for stopping the movement of sand is to create obstacles in the path of their movement, protecting newly planted vegetation from wind damage and ensuring stability during the initial years. In this project, various methods of preventing wind erosion, including creating a windbreak to reduce wind speed below the erosion threshold and sand spraying to increase the wind threshold, were evaluated in the dunes of Abuzidabad, Kashan, under severe wind erosion. The windbreaks used include mesh with a percentage of 50% porosity in a checkerboard with dimensions of 2.5 * 2.5 m, and cottonwood harvested from cotton fields in a grid of 5 * 5 meters. The height and distance of the windbreaks were calculated using the wind threshold speed and the maximum wind speed of the region. Sand spraying was tested on dunes and clay-salt panes with 50% and 30% density. To compare the rate of soil displacement in the above and control treatments, graded wooden indicators up to a height of one meter of sediment traps were used. In addition, the effect of net windbreak on the percentage of successful establishment of the Holoxylon sp. plant compared to the control was investigated. In this study, the cost of each method was calculated separately and compared with the cost of spraying oil mulch. The results showed that 50% sand spraying, in addition to having the best performance in stabilizing sands and preventing the formation of dust, as well as stability, also has a lower implementation cost than other methods. Therefore, the 50% sand spraying method is introduced as the best method to stabilize and prevent erosion at the lowest cost and also environmental compatibility.
S. Esmailian, M. Pajouhesh, N. Gharahi, Kh. Abdollahi, Gh. Shams,
Volume 28, Issue 2 (8-2024)
Abstract
Studying the process of soil erosion and evaluating its effective factors is one of the most important prerequisites for proper management of soil and water resources. This study was conducted to investigate the production of surface and pipe runoff and sediment using artificial rainfall on silt loam soil in the laboratory. So, the soil was collected from the study area and transported to the laboratory. Laboratory experiments were performed on a soil bed in a rectangular flume with three pipes, at slopes of 2%, 6%, 10%, 14%, and 18% under simulated rain (30 mm/h) for one hour. Related graphs were drawn in Excel to analyze the results, and Spearman's correlation test was used in SPSS software to check the correlation between runoff and sediment values in each slope. The results showed that with the increase in slope, the sum of surface and pipe runoff and sediment increased over time. For example, in a slope of 2%, the runoff and sediment in the initial moments of the experiment increased from 0 to 1.3 liters and 26.2 g m-2 at the end of the experiment. Also, the correlation coefficient between runoff and sediment in the slopes was 0.98, 0.62, 0.4, 0.93, and 0.15, respectively, which was significant in some, but in others, it was not significant because of soil loss.
A.r Vaezi, Kh. Sahandi, F. Haghshenas,
Volume 28, Issue 3 (10-2024)
Abstract
Water erosion can be affected by land use change and soil degradation by agricultural activities. This study was conducted to investigate the effects of land use change in poor pastures on soil physical degradation and water erosion in semi-arid regions. Experiments were performed in 42 soil samples taken from seven areas covering the two land uses: poor pasture and rainfed agriculture, which have different soil textures (clay loam, silty clay loam, sandy clay loam, silt loam, loam, sandy loam, and sandy loam). The physical characteristics of soils were measured in the samples of both types of land use and its changes were expressed as physical degradation of the soil. The soil's susceptibility to water erosion was measured under simulated rainfall with 50 mm h-1 intensity for 60 min. The results showed that the land use change in pastures leads to the physical deterioration of soils; so bulk density, porosity, macropore, field capacity, saturated point, aggregate size, and aggregate stability were degraded with a rate of 28, 22, 41, 11, 5, 62, and 63 percentages. The structural characteristics of soil (aggregate size and stability) had the highest physical deterioration due to the land use change in the pastures. The change in land use change greatly increased the sensitivity of soils to water erosion. A significant relationship was found between the susceptibility of water erosion and the soil's physical degradation. The soils with coarser and more stable aggregates have higher physical degradation by the land use change and in consequence show more susceptibility to water erosion.
S.m. Abtahi, M. Khosroshahi,
Volume 28, Issue 4 (12-2024)
Abstract
Today, wind erosion and dust are an environmental crisis, not just in desert areas but also in the entire country, and putting many costs. The combat against wind erosion in many desert areas by using oil mulches and the cultivation of compatible plants started in the 40s. However, the use of petroleum in addition to mulching the environmental problems, due to the high costs of purchase, displacement, and dispersion, is not economical. Therefore, the performance of non-oil and chemical mulch on dunes was investigated in Kashan. The research on fertilizer application of mulch under a completely randomized design includes: control (no mulch), a polymer mulch, potas, Fars, Paya, and Akrilik at 3 reps (3 sand hills) and the amount of erosion (with the help of the embedded indices in the hills), the survival of plants cultivated in the form of cuttings and seedlings, the percentage of humidity and temperature of each iteration were measured and variance analyses were performed. Field surveys and the results of the statistical analysis showed that the strength resistance of Fars, Paya, and Akrilik is almost the same. Observation of wood indices showed that Fars, Paya, and Akrilik mulches have almost the same strength in terms of wind resistance (almost no wind resistance). Fars mulch after 8 months of spraying showed small fractures due to the loss of flexibility. The study of soil temperature statistics showed that the treatments under mulch had no significant temperature difference compared to the control treatment. A comparison of soil moisture data indicated a high moisture percentage in the potash mulch treatment. The survival rate of cultivated plants was higher in Paya and Akrilik treatments. According to the results, Akrilik, Paya, and Fars mulch are recommended for sand fixation. One of the limitations of research in desert areas is the uncontrollability of environmental and human conditions. So, it is recommended to close the entire mulching area and use a mobile wind tunnel device at the project site to determine the wind slavery at different speeds.
A.r. Vaezi, F. Besharat, F. Azarifam,
Volume 28, Issue 4 (12-2024)
Abstract
The temporal distribution pattern of rainfall can play a role in the production of runoff and soil loss during rainfall. This study investigated four rainfall patterns: uniform, advanced, intermediate, and delayed rainfall under field conditions. The rainfall height in all rainfall patterns was 20 mm. In the uniform rainfall pattern, a constant rainfall intensity (40 mm h-1) was used and in the non-uniform rainfall patterns, a maximum rainfall intensity of 40 mm h-1 was applied for a 15-minute duration. The experiments were carried out in 60 cm × 80 cm plots on a hillslope with a slope gradient of 9% at three replications. Rainfall patterns were set up on the plots in five events with an interval of one week. The results showed a significant difference between rainfall patterns in runoff and soil loss (p<0.01). This difference was due to the destruction of surface soil structure and the reduction of water infiltration rate, especially during peak time of rainfall intensity (40 mm h-1). The highest runoff occurred in the delayed rainfall (3.43 mm) while, the highest soil loss (61.47 g m-2) was observed in the intermediate rainfall, which was associated with the peak intensity of rainfall at the end of the rainfall and its role in the destruction of the soil structure on the one hand, and the loss of infiltration rate on the other hand. Variation of runoff and soil loss from one event to another indicated that soil loss is in line with runoff production in uniform rainfall, while soil loss did not follow runoff in other rainfalls. Soil loss in these rainfalls was affected by both runoff production and availability of erodible soil particles. These results revealed the necessity of studying the rainfall intensity distribution pattern for accurate prediction of soil erosion and determining soil loss variation event by event in the semi-arid region.
J. Karimi Shiasi, F. Fotouhi Firoozabad, A. Fathzadeh, M. Hayatzadeh, M. Shirmardi,
Volume 29, Issue 1 (4-2025)
Abstract
One of the main factors contributing to water erosion is the inherent characteristic of soil erodibility. Erodibility depends on particle size distribution, organic matter, structure, and soil permeability. This research aimed to investigate changes in the soil erodibility factor across geomorphological facies. The soil erodibility index was estimated by sampling 58 points within the geomorphological facies of the Dorahan watershed, using the Wischmeyer and Smith method. In the laboratory, soil granularity distribution, organic matter, soil structure, the amount of gravel, lime, salinity, acidity, and sodium absorption ratio were measured. Results indicated that soil erodibility across the entire area ranges from 0.0148 to 0.0661 (t.hr/Mj.mm). The soil erodibility index (K) for the hro-p1 and hro-p2 facies is higher than for others and exhibits the widest range of variations compared to the other facies. The lowest range of changes within geomorphological facies is associated with the hrc facies. The erodibility index decreases from the east to the west of the basin due to the presence of exposed rock faces, which protect the soil as a cover layer.
S. Yousefi, S.n. Emami, M. Nekooeimehr, S. Mardanian,
Volume 29, Issue 2 (7-2025)
Abstract
In the present study, the Road Sediment Delivery Model (SEDMODL) and Geographic Information System (GIS) were utilized to estimate the average annual sedimentation caused by the forest road network in the oak forests in the west of Iran, Chaharmahal and Bakhtiari Provinces (Nazi forest road with a length of 5171 meters). Sedimentation from the study forest road network was estimated based on three basic factors in the model. Also, 30 erosion benchmarks were installed to measure the erosion and sedimentation rate at different distances from the road and in different parts of the study road and changes were measured during a year. The results showed that the average soil erosion at different distances from the Nazi road based on erosion benchmarks is 5.7 mm per year. In addition, the estimated erosion and sedimentation rate of the entire study road network based on the SEDMODL model is 2875 and 570 tons per year per kilometer, respectively. Model evaluation using erosion benchmarks showed that SEDMODL is a suitable model for estimating soil erosion on forest roads in the west of Iran (R2=0.78 and RMSE=0.73). It should be noted that statistical analysis of erosion hot-spot analysis showed that 39 percent of forest roads in Nazi showed very high erosion. Based on the results of the present study, it is suggested that conservative, protective, and road maintenance measures in areas with high erosion risk should be prioritized by decision-makers.
