نشریه پژوهش های آبخیزداری
پیاپی 131 (تابستان 1400)

Forms of erosion demonstrate its intensity. The study area is one of the suitable rangelands for animal husbandries in the Province of Semnan, which is subjected to a plethora of water erosion forms due to an overuse of the land. Therefore, it is necessary to investigate the effective factors in an aggravation of water erosion conditions in this area to manage and control it. Erosion in arid and semi-arid regions is intense; therefore, it is necessary to take action to inhibit or reduce it. As the forms of erosion are identifiable, we tried to determine the relationships between geomorphologyand forms of water erosion, namely: sheet, rill, gully and badland in a sub-watershed of the Hablehroodcatchment. Different classes of lithology, slope, aspect and elevation were correlated with any of forms of erosion in the area to determine their variety in the development and dominant erosion on each of the classes and each factor. Using the guidelines of the Land Degradation Assessment in Drylands (LADA), the forms of erosion in terms of its intensity was ranked and was used according to the typology of the variables. The Kruskal-Wallis test was on. The results indicated that the highly developed forms of water erosion, gullies and badlands, marl, gypsum and salt formations (8.4 and 15.8%), an elevation of 1000-1200 meters, the slope of 10-20% (8.7 and 15%) and the southern aspects domain (5.7 and 9.5%) respectively. The result of Kruskal-Wallis test for the slope and aspect at 0.01 and elevation at 0.05, respectively, were found to be significant, which indicated that there were specified differences in the forms of water erosion at the specified classes of geomorphologyfactors of the area. Therefore, geomorphologyfactors may be used to assess forms of water erosion and its intensity in similar regions.

Sediment production at each stage of erosion and its redistribution vary at different scales in a watershed, a slope and even a plot. The preparation of sediment budgets on watershed and slope scales have been considered in the two preceding decades, and a review of this tool on a plot scale can also help to better understand the process of sediment production, redistribution and delivery. The present study was conducted to budget sediments in laboratory plots with sandy-loamy soil and under rainfall simulation with the intensities of 30, 50, 70 and 90 mm h-1. Sediment tracing was performed on the surface of the plots by measuring the changes in the density of synthetic color-contrast aggregates using image processing. The results indicated the ability of this method to prepare sediment budgets on a plot scale. The contribution of interrill erosion in sediment production was increased with an increase in the rainfall intensity; however, the proportion of sediment redistribution within the plot was decreased. The average sediment delivery ratios for the rainfall intensities of 30, 50, 70 and 90 mm h-1 were 7.30, 8.54, 11.74 and 15.64%, respectively. The insignificance of this ratio on a plot scale was emphasized due to the short period of the experiment and should be considered in laboratory research projects.

One of the important challenges and issues in land management programs is that of physical growth of cities in different directions over time. The transformation of non-urban watersheds into urban ones has led to some environmental challenges and problems. An overall management plan needs accurate spatial information at consecutive times. Remote sensing technology offers great help in identifying and detecting land use changes. The aim of this study was to detect land use changes using images collected from 1991 and 2001 Landsat 5 satellite¢s TM sensor and 2018 images provided by the Landsat 8 satellite¢s OLI sensor over a period of 27 years on Abshuran Watershed, the Kermanshah. Following the required procedures in the preprocessing stage, a change detection map was prepared with an acceptable accuracy with supervised classification in the ENVI5.3 software environment. The results indicated that during the 2001-2018 periods, about 1.17 % of the share of the rangeland and farmland decreased and that the urban and residential lands increased from 5.92 % to 17.19 % of the total area. Most of the land use change has occurred in the urban and residential areas, thus an increase in the impermeable areas causes an increase in natural disasters such as flooding in addition to some negative effects on natural resources.

Healthily watersheds provide many ecosystem services in various fields, such as social and economic well-being; Therefore, we need to develop methods that can be used to determine the levels of health and sustainability of watersheds. The aim of this research was an evaluation of the sustainability of the Bakhtegan Watershed servicer using the watershed sustainability index (WSI) in a ten year periods of (2006 to 2016). The UNESCO – HELP demonstration has proposed an integrated watershed sustainability index (WSI), based on four criteria of hydrologic (quantity and quality), environmental, life, water policy issues and three parameters of pressure, status and, the response was used in order to achieve low, medium, and high levels of the basin¢s sustainability of services. The results showed that the pressure parameter with a score of 0.75 and the response parameter with the score of 0.45 had the highest and lowest scores for an assessment of the watershed¢s sustainability of services. Furthermore, the results showed that the criterion of quantity hydrological with a score of 0.25 and the environmental quality with a score of 1 offer the most and least priorities for its management. The value obtained for the WSI was 0.61, which represents an intermediate level of basin¢s sustainability of services, thus points to the need for more attention to the region's sustainability level.

Understanding the barriers in achieving people¢s persistent participation, resolving problems and participating in watershed management plans have an important role to play in increasing the effectiveness of the watershed management plans and reducing the related costs. Arad district is located in Ray County, the Province of Tehran, and is one of such areas where has been implemented the operational proposals from detailed studies of watershed management implemented. Several factors may contribute to a lack of people¢s participation in watershed management plans. These factors were identified by experts based on desk studies, queries from experts, as well as face-to-face interviews with residents of the area as four indicators and 11 sub-indicators, whereby their validity were confirmed by experts. These indicators were prioritized based on the fuzzy analytic hierarchy process method as well as the Friedman nonparametric test based on the expert group (28 experts) and the residents based on the sample size derived from Cochrane's formula (220 locals). The two-sample Kolmogorov-Smirnov test was also used to examine the agreement of the two views on the importance of the items. The range of consistency ratio of judgments and Cronbach's alpha varied from 0.035 to 0.079 and 0.710 to 0.815, respectively. Accordingly, the priority of effective indicators and sub-indicators on a lack of people participation from the viewpoint of expert and residents from the importance of high to low were determined and an agreement of the views was established. It is suggested that the solutions to remove the barriers of participation, be considered in the future detailed studies of watershed management in the study area based on the priorities presented in this investigation.

Effect of meteorological drought on vegetation conditions and their relationships with each other was investigated in the Province of Lorestan. The standard precipitation index (SPI) as a meteorological drought index was used for 28 rain gauging stations during the years 1987-2017 in that province. Benefiting from the remote sensing and MODIS images, the normalized difference vegetation index (NDVI) was extracted for the years 2000-2017 and the vegetation condition index (VCI) was calculated. Using the SPI results, the dry, normal and wet years were identified and the index year was selected for them. The correlation between the SPI and VCI was investigated using linear regression. The results indicated that the highest correlation coefficient of Pearson was related to the VCI in March with a 9-month SPI in November was equal to 0.64; the correlation coefficient between the multivariate linear regressions of the SPI with VCI in June was 0.7. The results of multivariate linear regression indicated that the SPI had a significant correlation with the VCI at the five percent level over a period of 9 and 12 months. A confusion matrix was used to evaluate the compatibility of the SPI drought classes with the VCI; the results also indicated that the highest compliance of the VCI with the SPI was in the moderate drought class. Furthermore, the results of this study indicated a 9-month delay in the meteorological drought index with satellite drought index at the 5 % level significance of the SPI with the VCI, which indicates that the VCI may be used in the absence of meteorological indicators for the study area.

The purpose of this research was to model and predict land use/cover changes using the LCM model based on two management scenarios, namely the sustainability scenario and the agricultural increase scenario in the Tajan Watershed, the Province of Mazandaran. Landsat satellite images and the data collected by the TM and OLI sensors were analyzed for 1991, 2010 and 2019. Images from the three-time periods were categorized into five categories: residential, farmland agricultural, forest, orchard, and rangeland. Land use forecasting for 2019 was performed using the 1991 and 2010 land use maps in the LCM model. The LCM model uses the perceptron multilayer neural network to construct transmission sub-models, map the probability of transmission, and ultimately predict the land use changes. Spatial variables such as distance from a road, distance from a river, slope, altitude, distance from a village, and distance from farmland were used as the influencing factors on the neural network changes. The land use map of 2019 was used to validate the model, which resulted in the Kappa and ROC coefficients of 0.84 and 0.89, respectively. The modelling results based on the sustainability scenario show a 5.74 percent decrease in the rangeland area and a 9.17 percent growth in the orchard area over the next 20 years, while the second scenario showed an increase of 8.61% in farmlands and a decrease of 5.59% in rangeland areas. Therefore, both rangeland and forest areas are declining and farmland and residential areas are increasing. A better land use management will require conservation scenarios in different parts of the watershed.

Knowledge of the flood discharge rate is of the utmost importance in water resources utilization and flooding damage mitigation studies. Therefore, the aim of the current research was mainly to assess the Analytical Hierarchy Process (AHP) method to predict the flooding susceptibility of the Amughin Basin, located in the Province of Ardabil. The basin¢s area is approximately 78 km2. The curve number (CN) of the basin was found by integrating the land use maps with the soil hydrologic groups namely: B, C, D. The CN was estimated 78.7 the year for 2015. Different effective factors, namely: the slope percentage, land curvature, distance from the river, topographic wetness index, stream power index (SPI), and the CN were used in the application of the AHP method, and the effective layers were classified into nine classes. A flooding into susceptibility map was constructed and classified into five classes with very low, low, moderate, high, and very high susceptibility. The results indicated that the CN was the most prominent in flooding susceptibility; the distance to the river and the amount of rain occupied the next priorities. The lowest factor in the flooding susceptibility was related to the plan curvature. Moreover, the results indicated that about 0.64% and 4.4% of the study area were categorize with high and very low sensitivities, respectively.

Several methods have been introduced to control soil erosion. One of the newest methods used to control soil erosion and reduce runoff is the use of polymers.This study was conducted to determine the effects of different rate of Polyacrylamide, PAM, (0, 0.2, 0.4, and 0.6 gm2) on marl soils in rainfall different durations (10, 20 and 30 minute) using FEL3 rainfall simulator with rain high intensity 120 mm/hr at Laboratory. The results showed that all of the PAM levels (0, 0.2, 0.4 and 0.6 gm2) in the three rainfall durations (10, 20 and 30 minute) had significant differences in decreasing splash erosion in comparison with control treatment. However, the interaction effect of rain duration and PAM levels, were not statistically significant. Low rate of PAM (0.2 gm2) cannot control splash erosion as well as, however decreased it less. The statistical analyzes showed there was no statistical significance noted at a rain duration of 10 min, however at rain duration 20 and 30 min, with different amounts of PAM, there was a significant difference in splash erosion control. When rain duration increased from 10 to 30 minute, the splash erosion enlarged. So, the splash erosion decreased due enhancement of PAM level, as the most effect was observed in rain duration 30 min and 0.6 gm2 PAM rate respect to control treatment which is 21.2% effective in decreasing erosion. This reduction was statistically significant at 95% level with Duncan test.

A quantitative method is presented to evaluate the ability of plants for rill and gully erosion control in the Moghan region in the province of Ardabil. This research was carried out during a five-year period (2016-2020). Five indicators, namely, stem density (SD), topsoil erosion-reducing potential of plant roots during the concentrated flow erosion (RSD), sediment obstruction potential (SOP), index of plant stiffness (MEI), and root cohesion (Cr) were calculated for 20 native plants of the region (SD=1.411×10-4 – 0.28, RSD=6.68×10-24 – 10.1076, SOP=8.275×10-5 – 0.696, MEI=1.69×10-6 – 27.134 N, Cr=5.432×10-4 – 34.626 Pa). Tamarix ramosissima Ledeb., Salsola dendroides Pall.,Artemisia fragrans Willd., Stipa arabica Trin. & Rupr. var. arabica, Alhagi camelorum Fisch., Verbascum stachydifome Boiss. & Buhse., Festuca ovina L., and Melica altissima L. are very appropriate species for controlling rill and gully erosion. Festuca ovina L., Stipa arabica Trin. & Rupr. var. arabica and Melica altissima L.have a distinct potential to obstruct sediment inflow into channels at the gully outlets. As each species has a particular ability in one or more of the indices, combined planting of selected plant species may be more effective in erosion control. The results of this study may be used in adjacent regions and under similar cold-semiarid and cold-arid environments.