مجله علوم و مهندسی آبخیزداری ایران
پیاپی 49 (تابستان 1399)

Flood zonation mapping is one of the priorities for the soil and water management, which Remote Sensing (RS) capabilities are very applicable to this issue. The main objective of this research was study of accuracy of the Object oriented and Pixel based methods for flood zonation mapping in the Taleghan River basin. Therefore, the Sentinel 2A satellite image of the study area classified using supervised classification method based on the both Object oriented and Pixel based approaches, with the Random Forrest (RF) and Support Vector Machine (SVM) algorithms. The overall precision and Kapa Coefficient of the RF algorithm based on Object oriented method were 89 percent and 0.82 and based on Pixel based method 88.5 percent and 0.75 respectively. The results of the overall precision and Kapa Coefficient for the SVM algorithm based on Pixel based method were 84.5 percent and 0.73 and based on Object oriented method were 86 percent and 0.78 respectively. In order to verification of the generated flooding zone maps, the flooding zone maps resulted from the hydraulic flood zonation mapping method with 2,5,10, 25 and 100 year return periods have been used. The results shown that, the generated maps of the both RF and SVM algorithms based on object oriented method; have the most suitable overlaps with the all-return periods flooding zone maps

Constraints on water resources and increasing the number and variety of water users has led to appeal of the importance of optimal water allocation. The Khanmirza watershed in Chaharmahal Va Bakhtiari Province, has experienced unsustainable development by relying on groundwater resources.  As a result of this imbalance, a dramatic drop occurred in the aquifer of the Khanmiza plain. The Khanmirza watershed allocation model in WEAP environment were developed to investigate the allocation and spatial changes, considering the base year (2015), the horizon year of the plan (2025), and the one-month timeline. The four scenarios examined in the WEAP model included the reference scenario, pessimistic scenario, optimistic scenario and realistic scenario over the next ten years. The results showed that 51 million cubic meters of demand, in a pessimistic scenario, 79 million cubic meters, in an optimistic scenario, 30 million cubic meters, and in a realistic scenario 41 million cubic meters cannot be provided. Therefore, given the high volume of water requirements in the agricultural sector, the need for special management and planning in this area to prevent groundwater loss is quite tangible. It is also clear that the use of water for agricultural in the studied area acts as a competitor to the environment and without land use management, water management will face tension.

By numerical simulation of the phenomenon of failure of dams and the flow of their flow, it is possible to design more precisely the structures and their location. The purpose of this study was to investigate the wave propagation phenomenon due to the failure of the rocky mortar-watering dam in the Marivan sub-basin of Zarivar in two-dimensional and three-dimensional models using the Fluent model. The results showed that the k-ε Standard model, with the lowest RMSE value, has more accuracy in simulation. Also, the study of the diffusion of flood damages in muddy water shows that the wave formed as a jet of sharp and daggle shapes downwards and the velocity of the forehead in muddy mud is much higher than water There is no contamination of the mud, which is due to the formation of the shape of the aerodynamics of the forehead in muddy mud, which causes more flow velocity due to the failure of damaged dams and can lead to further destruction of the bottom dams of the watershed. The results showed that the fl ouent model has an acceptable accuracy and ability to simulate dam failure in both wet and dry substrate conditions.

Co-management of water resources is one of the most important managerial approaches in water resources; its achievement requires the strengthening of social capital; also, the role of water resources Local Stakeholders in increasing the amount of this capital is undeniable. The social network analysis approach is one of the strategies that will examine the pattern of relationships between Local Stakeholders in planning, policy making and successful implementation of participatory water resources co-management. In this research, the social relationships between 143 farmers of Gezir village, Bandar-Lengeh province, which are used by indigenous structures for irrigation of the palm groves, have been investigated using the network analysis and network level measurements (density, Reciprocity and average geodesic distance); The data of this study were collected in the fall and winter of 1396. The results represent the favorable social capital that the optimal amount of this capital derives from the applicability and importance of the indigenous community structures, in particular the cistern structure, for managing water resources through strong links of Consultation (rainfall time) and Collaboration in the affairs related to these structures. Therefore preserving the collective indigenous structures water resources will strengthen social capital and increase Resilience to tensions for water resources co-management.

In this study, in order to examine the joint of the cable and the collar in control of scour around the bridge piles, experiments were carried out in a rectangular plexiglass flume as a direct path. The experiments were carried out using three different cable diameters, three different thread angles and three rounds of the cable threaded at a steady current in clear water. The results of this study showed that, installing a cable and collar around the base of the cylinder is an effective factor in reducing the depth of scouring around it. Also, in all conditions of use of cable and collar, compared with the without collar mode, it increases the percentage of reducing scour depth around the cylindrical base. The use of collar on average reduces scour depth by about 43 percent compared to without collar condition. Also, the maximum scour depth in cable and collar conditions at a thread angle of 15 degree, a diameter ratio of 0.1 percent and triple threaded was about 63 percent.

Every scientific discipline usually focuses on problem solving which eventually plays a crucial role in order to improve research policies and planning. Evaluation of such improvement could enhance research activities. The trend of scientific research and their subjective trajectories in watershed management were analyzed by content analysis method. This study seeks shortcomings of this discipline in the two most seminal universities in Iran (University of Tehran and Tarbiat- Modares University). The results could lead policy-makers to a better scientific strategy and modify issues show universities emphasized on the state of problem which refer to second order catchment and their sub-catchments problematic issues. Erosion-sediment sub-code and regime (hydrology) sub-code are the most reputed ones in University of Tehran and Tarbiat-Modares University respectively. Overall trends more tend to hydro-technical, geomorphological and hydro-meteorological issues. It concluded that problematic issues in the universities focus on processes and their implications instead of focusing on the final outputs which were produced by models (e.g. erosion models). Socio-economic problems would contribute more in the study of human-nature relations.

In this research, fractal relationships were used to evaluate the particle size distribution of the check dam. Three check dams with height of 2, 2 and 2.6 meters were selected and the hole was drilled same the height of the check dam at the sediment deposits. Then, depending on the color of the deposited layers, the thickness of the layers was determined and sampling was down from each layer to determine the particle size distribution. The fractal relationship of Bird et al. Provides better results than other relationships. In all three check dams, the fractal has increases and decreases from the top to bottom layers and does not change uniformly. In check dam 79 and 80, there is a significant negative and positive relationship between the fractal dimensions with the percentage of gravel and sand respectively. In check dam 81, the fractal dimension has negative relation with gravel and positive to sand. Generally, soils with less gravel particles and more sand have more fractal dimension. Comparison of the sedimentary layers of check dam 79, 80 and 81 shows that the process between the fractal dimensional return points and the sand particles is similar to the linear trend of sand particles.

In recent decades, low-yielding rainfed farms have become known as the main sources of sediment production and soil erosion in the country. Therefore, more research is needed on the factors affecting erosion and sediment production in these areas. This research was carried out with the aim of studying the effects of slope and rainfall intensity on erosion between rainbow trout in test farms in Kermanshah provinces using field descendant simulator. In a preliminary study, the erosion situation in the high slope drilands of the province was studied by field observations. Then, in some representative fields (in terms of erosion, slope and climate class), the status of erosion and agronomic management and its components were examined and soil sampling was carried out. 11 farms were selected in the current management conditions and in the dominant slopes (10 to 30%), and rainfall simulator test were performed in these farms and erosion and runoff were measured. The results showed that in sloping fields, the percentage of crop residue and slope, respectively, significantly controls the process of runoff production and soil erosion.

Surface water resulted from rainfall-runoff responses in a basin is a potential water source that if it is managed properly can be useful to demand secure. In this study, hub coating algorithm (PR) and geographic information system (GIS) were used to identify areas with potential in Birjand plain for rainwater harvesting. The weight of 18 decision-making indices was calculated and prioritized using TOPSIS method.  After determining the weight of each of these indices for locating rainwater harvesting potential, indices maps were prepared in Arc GIS 10.3 software and then for final mapping of rainwater harvesting potential of Birjand plain, points having common characteristics of 6 highest weight indices were determined. In total, 220 points were extracted as the best points from the TOPSIS method. Using the hub overlay method with algorithm (pr) and coding in Matlab environment, out of 220 points, 20 points were identified as suitable locations (hubs). Finally, the final map was drawn by inserting these points into ArcGIS software. The results showed that in the north and northwest of Birjand, the soil has a high capacity for rainwater harvesting, these areas mainly have sandy-pebbly soil texture, high permeability, moderate rainfall and residential land use.

This study was conducted to investigate the effect of slope gradient and soil physical properties (grain size distribution, bulk density, aggregate stability and permeability) on water erosion in the furrows of rainfed farms under fallow conditions. The furrows with 6 m length were installed in five rainfed farms with 6.1, 10.6, 14.8, 20.7 and 27.1% slope steepness at three replications. Results indicated that rill erosion were significantly varied among the five farms. There was no significant correlation between rill erosion and slope gradient, while it was significantly affected by some soil properties consisted of sand (P<0.05), clay (P<0.05) and aggregate stability (P<0.05). These results revealed that in coarse textured farms with different slope gradient, soil loss through furrows isn’t significantly related to slope gradient, but it is significantly affected by soil physical properties.