نشریه پژوهش های آبخیزداری
پیاپی 119 (تابستان 1397)

Gully erosion is a serious threat to the society and environment of the study, primarily caused by surface runoff and dramatically accelerated due to rugged topography, soil properties and human induced factors. Therefore, the objective of this study was to investigate hydrologic processes affecting gully formation by topographic indexes in arid regions of the Markazi Province. Then threshold of the slope -area in the gully regions of Robattork and Pik-e Zarandie were determined. A logarithmic equation was developed using the morphometric characteristics of the gullies, the slope-area relationship at Robat-Tork was highly correlated and the b coefficient was negative. The investigations revealed surface flow with dissolution action was involved in this area. In the Pik-e Zarandie region, this correlation wasn't strong, but it was significant at the level 95%. In this region, the effect of surface flow and dissolution phenomenon on the gully formation was also evident. In addition to the importance of the climate, gully categorizing based on land use can be achieved with better models. Therefore, it is necessary to determine the indices of topographic thresholds that best reflect the conditions of the local physical environment and land cover/use.

The success of soil conservation and watershed management programs requires the understanding of individuals’ attitudes towards these programs. Therefore, the goal of the current study was evaluation of the attitude of the residents towards watershed management practices in the rural areas in the Khorasan Razavi Province using a cross sectional survey. The required data were collected from 60 respondents who were randomly selected in two watersheds through personal interviews by a questionnaire. Descriptive and factor analysis were used to analyze the data. Findings showed that the knowledge level of the respondents about watershed management practices were satisfactory. Also, the acceptance level of watershed residents was moderate. Factor analysis showed that priorities of the residents towards watershed management programs were the economic, social, and educational service items. Data analysis discovered that these factors explained 66% of the variation of reactions to the programs.

The aim of this study was to discover the Obstacles of local community’s participation in biological restoration and desertification control plans in the Lapui County, Fars Province. The study is an applied research in terms of purpose, a survey study in terms of collecting data, a field study in terms of controlling variables, and a exploration study in terms of research method. The statistical population of the study consisted of 600 active households of Sustainable Development Cooperative in the Lapui County. Using the Morgan's and Krejcy's tables, the sample size was determined to 234 households. The data gathering tool was a questionnaire whose validity had been confirmed by a panel of experts, and its reliability was confirmed by the Cronbach's alpha coefficient (α > 0.7). The data analysis was conducted by using the SPSS18 and AMOS software. In order to analyze the results, in descriptive section, the centrality (mean and mode), and the dispersion (range of variations, variance, and standard deviation) statistics were calculated, and for the inferential part of the analysis, an exploratory factor analysis was used to factorize the barriers. Results indicated that the most important barriers to participation of local communities in the carbon sequestration project can be identified in six categories: lack of mutual trust and belief, lack of awareness and information channels, administrative and institutional barriers, the implementation barriers, lack of government support, and lack of community needs assessment and satisfaction, which explained a sum of 83.36% of the total variance. The credibility of these barriers was also confirmed by the confirmatory factor analysis.

Estimating the runoff height potential is important for managing and predicting the flooding of an area. In this regard, the US Soil Conservation Agency (SCS) has provided a method that is very suitable for areas lacking hydrological data. Conventional runoff measurement methods are very costly, time consuming and difficult. The purpose of this study was to calculate the flooding potential and draw a map of the Nazlouchai Watershed curve number by the SCS method. Land use map of the area was compared with the index table and integrated with the soil hydrologic group data, and the runoff curve number, an important factor in the SCS method, was obtained. In the next step, the average rainfall curve number, and runoff height were calculated, and the results were zoned according to the curve number and runoff height maps. Using the Geographic Information System, the average weight of the area curve number was estimated as 96.77. Results showed that the highest amount of runoff curve number under the average humidity conditions in the study area was 100, and the lowest value was 56.00. The high mean value of the area curve number indicates the low permeability of the area, which indicates the strong likelihood of flood occurrence.

Study of water balance is absolutely important for investigation of the hydrology cycle, and preparation of water balance components in the watersheds requires many spatial data and their analyzing; so new technologies, models and tools such as GIS are needed. In this study, the SWAT model, which is a conceptual and semi-distributed model in the water and sediment balance simulation, was used in Aharchay watershed, Ahar, East Azarbayjan Province. Efficiency of the model in hydrologic simulation for this area is evaluated. Meteorology and hydrometers data of 1979-2010 was selected for this simulation; the average amount of rainfall and evapotranspiration were obtained 559.8 and 299.1 mm respectively. The period of 1982-2002 were used for calibration and 2003-2010 for validation. Calibration and validation processes were performed using SWAT-CUP software and PSO algorithm. Nash-Sutcliffe efficiency coefficients for water simulation were 0.39 for calibration and -6.7 for validation. Results showed that water balance simulation was not performed perfectly. Deficiency of required information and use of different data periods in calibration and validation were some of the effective factors which reduced the efficiency coefficients of the model.

The vital need for river management and prediction of bank erosion processes is obvious. Riverbank erosion is one of the major sources of sediment for many rivers across the world. In this research, a combination of morphology methods, satellite imagery and BSTEM model were used for stability analysis of Bashar River. Comparison of the results of the BSTEM model indicated that the averages of maximum lateral retreat in cross sections of 1 to 5 were 128, 210, 200, 37 and 65 cm; the average of total eroded area were 2.01, 4.1, 5 36, 0.7 and 2.65 m2; the failure width were 1.73, 3.12, 2.32, 8.56 and 2.65 m, and the factor of safety were 0.34, 0.33, 0.27, 1.07 and 0.79, respectively, indicating the instability of the studied cross sections. On average, the maximum lateral retreat and the minimum factor of safety occurred in the floods peaking at the 537 and 912 m3/s, respectively. The results of the application of the BSTEM model in the selected reach indicated the instability of this reach of the river.

Climate change will lead to an intensification of the global hydrological cycle and can have major impacts on regional water resources, affecting both ground and surface water supplies. A better understanding of hydrological changes associated with climate change can be achieved by analyzing the temporal trends in river discharge time series. We used the parametric test (regression analysis) and non-parametric Spearman's rho, Mann- Kendal and TFPW Mann- Kendal approaches to evaluate annual and seasonal trends in river flow data from 22 sub basins (based on the classification of the Ministry of Power) located in the southern regions of Iran over a 31-year period spanning the hydrological years 1981–1982 to 2001–2013. The data used include pan evaporation, discharge, minimum and maximum air temperatures, depth, intensity and duration of rainfall at each sub basin. Results showed that in more than 50% of the hydrometric stations, runoff had a decreasing trend. This trend was apparent in the central watershed consisting of Bandar-Sedij and Kol-Mehran sub basins. Conversely, more than 90% of the stations, duration and intensity rainfall had decreasing and increasing trends, respectively. Furthermore, minimum and maximum air temperature trend had an increasing while evaporation had a decreasing trend. In conclusion, factors influencing the declining discharge trend can be changed by changing the rainfall pattern, decreasing the rainfall duration and increasing its intensity.

The use of vegetation cover for the sustainable riverbank stabilization is not only economical in most cases, but also ameliorates the landscape. The purpose of this research was to evaluate vegetatative stabilization of the Ferizi River, s erodible banks. Considering that each vegetative form offers a unique type of protection, 8 grass species, short shrub and a tree species were selected for this research. Salix eleganos Scop.,Salix alba L. Elaeagnos angustifolia L. were planted at suitable spacing on the banks. A plot without vegetative protection was established as the control steel pins with specific lengths were driven in to the banks at two rows and three cross sections. The depth of erosion was measured monthly for 4 years by an increase in the length of the pins outside of the river side on transects. The flow data were collected at the hydrometry station. The results indicated that shrub and tree cover performed satisfactorily in stabilizing the riverbank. The erosion depth for the shrub and tree cover was <1% of the control; this was 50% for the grass cover; therefore it was not as effective in erosion control as we had expected. The reason for this poor performance is due to the growth season of these grass species which is not synchronized with flooding season of the Ferizi River. It is interesting to note that the study duration coincided with the 5-year flow regime of the river.