فصلنامه پژوهش های فرسایش محیطی
پیاپی 3 (پاییز 1390)

Wind erosion due to lack of rainfall is one of the most significant desertification processes in many parts of the world Iran, because of its latitudinal location geographically and lack of rainfall, is faced with this dilemma. Recent droughts in Hormozgan Province have destroyed sparse desert vegetation and increased the process of desertification, which resulted in wind erosion in the vulnerable areas, causing destruction of shrubs and trees in East Jask. The increase in sand dunes have threatened area villages, causing villagers to immigrate. Remediation which has been taken in Iran until now was related to stabilization of the shifting sand by oil mulch. We have examined the possibility of replacing oil mulch, which is more expensive, with polymer polylatise to stabilize the shifting, wind driven sand taking into consideration the climate (humidity) of Hormozgan Province. To do this, we chose three plots, each 1000 m2 located in Gahrdo plains, Sirik, Hormozgan Province. The plots consisted of two treatment plots and a control plot. In the first and second treatment plots, we placed measured indicators and planted and irrigated seedlings, followed by spraying polylatise as mulch. Supplemental irrigation was the difference between the first and second treatment plots. Supplemental irrigation seedlings were planted at the end of the test period, in order to determine the effect of manual irrigation in protecting polylatise against soil erosion. The third plot had no mulching and installation of measured indicators as the control plot. During the five-month test period,the existing indicators were measured in ten different periods. After data collection, the distribution was selected according to the data. Then, analysis of various parameters by using Excel software was performed to determine significance of the collected data. Results showed that the ratio of index change from the beginning to the end of the study in the control (no mulch) plot constantly fluctuated. However during this period in the mulched areas the index number was maintained at baseline (zero) and no changes were noticed

Gully erosion is one of the geomophological phenomenon that causes numerous losses to farmland, rangeland, roads, and increased sediment rate. Recognition of the causes and modeling gully erosion has an important role in watershed management, which aids in preventing the destruction of lands in sustainable development. In this research, a gully erosion map was prepared with the use of airphotos at a scale of 1:40000, IRSsatellite images, and a field survey with the use of GPS. Initially, with respect to the lack of comprehensive research and an investigation of prior research,factors such as lithology, slope, land unit, aspect and landuse were studied. Then, by using the analytical hierarchy method, the impacting factors were binary compared with each other. A weighted coefficient for each factor was computed. Finally,we prepared a gully hazard zonation map and watershed model. The results of this investigation showed that marl silt and old Makhroot Afkana (100%) and land type Tapa Mahoor (57%) are effected by gully erosion. In the investigated area, this study showed that the majority of gully erosion influenced:i) land that had a slope of 5%-20%(which consisted of approximately 92% of the entire land area)ii) land that had a southern slope (82%) and iii) poorly covered range land (100%). The analytical hierarchy method is a suitable model for determining gully erosion susceptibility in the Aliabad catchment.

Splash erosion is recognized as the first stage in the process of erosion that results in bombardment of the soil's surface with rain drops. Two basic processes in soil erosion are the dispersement of soil particles by rain drops and the changes caused to the soil's structure, which are then moved by runoff. In this research,the effect of various polyacrylamide (PAM)values (0, 0.2, 0.4 and 0.6 g/m2) on the amount of splash erosion at two rain intensities (95 and 120 mm/h)by the use of laboratory generated rain (FEL3)were analyzed. Experiments were undertaken with marl soil. After calibrating the rainfall simulator, soil samples were weighed and treated with PAM. Next the effects of rainfall intensities at95 and 120 mm/h for 10 minutes were studied. Initially samples were oven-dried for 24 hours, at 105ºC. Next, samples were reweighed to determine the amount of soil lost. According to the results, there was no statistical correlation between rain intensity at 95 and 120 mm/h and decreased soil erosion.Howeverthere was a relationship between the different amounts of PAM (0, 0.2, 0.4 and 0.6 g/m2 ) and splash erosion control. The most effect on controlling splash soil erosion was seen with PAM at 6 kilograms/hectare when compared with 2 and 4 kilograms/hectare, which is 28.93% effective in decreasing erosion. The main two factors, intensity and treatment,were not statistically significant. There was no statistical significance noted at a rain intensity of 95 mm/h. Howeverat a rain intensity 120 mm/h, with different amounts of PAM, there was a significant difference in splash erosion control at 4 kilogram/hectare which had a maximum effect of 40% in controlling soil erosion.

Substantial population growth and urbanization arbitrarily banning the exploitation of natural resources and environmental factors adversely impacts the environment and resources necessary for nutrition and healthy life styles. The secret to success and survival of ecosystems depends on a stable, continuous monitoring of the environment. The SWOT model has been developedto consider all internal and external aspects. In this study, to analyze land use and cover changes in Taleghan,we have used SWOT as a qualitative approach to develop sustainable land management. Taleghan is a town in Alborz Province located within the Taleghan watershed. Referring to the SWOT analysis matrix sustainable tourism development was presented as the best strategy for SO,imposed regulations of soil and water pollution by the health centers as the best strategy for ST, avoidance of land use changes as the best strategy for WO, and finally the range management plan to reduce surface both runoff and soil erosion as the best strategy for WT.However, the proposed diagram of sustainability (IUCN) has two indicators,the ecosystem's quality and acceptance and lifestyle desirability which is based on the ecological features and indigenous areas rooted in public participation. Based on the above indicators, the presented solutions are more realistic which prevent disturbance to the ecosystem's natural balance which leads to sustainable development, notable in the marshes of Taleghan.

This study is aimed at estimating suspended sediment load in watersheds using hydro-climatic factors with the intent to determine spatial and temporal variations of sediment yield in Qarah Su drainage basin, Ardebil Province. For this study, data from seven rain gauge and hydrometric stations during a 22-year period were used. The research was based on statistical regression analysis between variables of precipitation, discharge and sediment load using SPSS software, extracting optimal model according to high correlation and acceptable significance.The results indicated very poor correlation between the mean rainfall and mean suspended sediment load in the studied stations. In contrast, discharge showed moderate and significant correlation with the suspended sediment load, which in the best condition,it explained 52% of the precipitation variations. Results of spatial variations showed that Dostbaglu station with average annual sediment load of 1749/79 tons per day had the maximum sediment yield. Lay station with an average annual sediment load of 1/7 ton per day had the minimum sediment yield in the studied basin. Temporal variations showed the highest sediment load rate in April and the in July. Variations in annual sediment load have an increasing trend in Lay and Pole Soltani stations, whereas other stations have a decreasing trend. The discharge trends showed an increasing mode only in Lay station. Meanwhile, with the exception of the Samian station, variations in annual precipitation in the stations showed increasing trend, which has considerable difference with the trends of sediment load and discharge.

Erosion is a surface-leveling phenomenon where thetransportof sediments from being washed off the land or by the force of gravity move from elevated areas. During different periods, in Iran, constantly flowing water has been affected by erosion. Thus it is important to address the erosionproblem. This research attempts to assess and identify the parameters affecting erosion in Haji Abad Watershed (Hormozgan Province). Investigation of the kind of mathematics-based analytics determined the most important parameters affecting erosion: slope, geology, soil type, and plant. In the basin, this study identified and subsequently used AHP and health weight category, which were important to all evaluated classes, which were statistically determined. Next, by using the Entropy Shanonmodel, the amount of distribution of unbalanced classes in each one of the effective parameters of erosion in the basin under study were clear. The results show that in a slope greater than 15%,with the entropy coefficient of 0.53 there is a balanced distribution in the basin and the amount of erosion in different parts of the basin are influenced by the slope. The geological formation in the basin, the quaternary formation and erosion are more susceptible than the entropy factor of 0.635 distribution in the basin, which are almost balanced. In addition, to soils with light texture (ratio: 0.94), and on land and pasture catchment (ratio 0.90), both of which have a high erosion, have a normal distribution. We presented methods for erosion management in the watershed.

In this research we aimed to study the sedimentology of Jajrud River, upstream from Latian Dam. Initially, a field review was conducted to ascertain complete familiarity with the geographical and geological conditions of the proposed region. After determining the sampling location, the acquired samples were taken to the laboratory. From morphoscopic studies of the sediments, we have determined that particles often undergo changes during the river course. Hence these changes do not adhere to a particular process. Since Jajrud sediments enjoy diverse lithology with plenty of channels and waterways included, therefore it is natural that particle changes do not have a particular process. This is also due to the fact that particles with chemical composition and diverse mineralogy possess different resistances, sizes and primary shapes. The distance that particles cover are diverse, hence they would not remain the same due to the effects of erosion and corrosion. Jajrud River in the proposed study limit, has a 10.1 torsion coefficient, an average incline of 4%, the presence of abundant dams in its own bed (dam parameters more than 1), an average annual discharge (119.7 cu.m/sec during September and a maximum 6.208 cu.m/sec during April) the type of sedimentation (lack of suspension), and a mutilated river with a gravel-sand bed. Congruent quantity of heavy minerals is decreased in the final stage compared to the initial stages. It seems that heavy minerals, due to their particular high weight, are sedimented more in the initial stage and their quantity is decreased in the final course. Additionally, the quantity of magnetic heavy minerals (iron oxides) are decreased towards the utmost end, most likely due to the particular rust above them as well as increased sedimentation at the initial stage.

Soil organic carbon (SOC) is a principal component in soil quality assessment. Knowledge of SOC and total nitrogen (TN) stocks are important keys to understand the role of SOC in the global carbon cycle and, as a result, in the mitigation of global greenhouse effects. SOC and TN stocks are functions of the SOC concentration and the bulk density of the soil that are prone to changes, influenced by land use changes, and soil erosion processes. This study has evaluated SOC and TN stock under different land use types and soil erosion types at catchment scale.SOC and TN stocks were measured in 112 different sampling sites of four main groups of land use/soil erosion: rangeland/surface erosion, orchard/surface erosion, dry-farming land/surface erosion, and rangeland/streambank erosion at Hiv and Zidasht catchments, Iran. The results showed that SOC and TN stock under all land use and erosion groups was significantly different. SOC and TN stock was greatest in the orchard land use and the total SOC stock for the 20 cm soil layer under different land uses and erosion types varied for Hiv in order of orchard/surface erosion (46), rangeland/surface erosion (31), and rangeland/streambank erosion Mg/ha (p<0.005). For Zidasht, the variance was, in order:orchard/surface erosion (43), dry-farming land/surface erosion (23), rangeland/surface erosion (23), and rangeland/streambank erosion 22 Ton/Hector (p<0.005). The TN stock has the same trend in all studied land use and erosional groups. Therefore it was concluded that rangelands were affected by erosion, with a subsequent decreasein productivity level. These results can be useful as a scientific basis for selecting the proper soil erosion control methods as a simple, low-cost approach to mitigate SOC and TN loss.