مجله علوم و مهندسی آبخیزداری ایران
پیاپی 60 (بهار 1402)

In the present study, the effect of sand extraction from the bed and bank of Khatirkuh river in Mazandaran province on social, ecological and environmental issues was investigated using a questionnaire and field visits, experts and local people. Then, by determining the sample size using the Cochran relation and evaluating the reliability and reliability of the questionnaires by Cronbach's alpha method and finally its validity was confirmed by experts and professors. Then 70 questionnaires were distributed between local communities and experts and using the SWOT matrix of external and internal factors, strategies for the effects of sand extraction in the region were identified. The results showed that the total secondary coefficient of strengths and weaknesses were 1.938 and 1.076, respectively, and the total secondary coefficient of opportunities and threats were 2.307 and 1.907, Respectively. According to the SO and WT factors for development planning in the region, offensive strategy is a priority. The above strategy maximize  opportunities and strengths and thereby reducing mining problems.The most important ecological factor of this region is the entry of invasive plants, forest and pasture fires, which have reduced growth, vegetation density and pasture destruction. The most important strength of  mining in this region is direct  and indirect employment related to sand and gravel mines.

The purpose of this study is to investigate landuse changes in Gorganrood basin in 2001, 2010 and 2019. Using Landsat and Product-Modes satellite images, used maps were prepared using the classification method of random forest algorithm in Google Earth Engine. Satellite imagery was classified into eight classes including forest, cropland, shrubland, grassland, wetland, urban, barren, and water. The results showed that the highest landuse area in 2001, 2010 and 2019 is related to cropland, respectively, equal to 3150.58, 3403.8 and 3031.82 square kilometers, and lowest amount in 2001 is related to water with an area of 84.67 and in 2010 and 2010 is related to wetlands with an area of 167.98 and 118.7 square kilometers. Comparison of the results showed that the urban landuse study period in 2019 compared to 2001, it has grown by about 34% (341 square kilometers). Also, forest lands at a rate of 5.5 percent (148.92 kilometers), shrubs at a rate of 8.7 percent (135.79 kilometers) and arable land at a rate of 3.8 percent (118.76 kilometers) had a negative growth.

The present study used Flow-3D to investigate the effect of installing netted collars with different shapes on bridge piers. The results showed that installing netted triangular, circular, square, and rectangular collars with a hole diameter of 0.1 (d/D) reduced scouring by 49.5, 52.2, 52.7, and 56.5 percent, respectively, compared to the case with no collars. A hole diameter of 0.15 (d/D) for the same shapes resulted in reductions of 46.1, 43.3, 44.2, and 49.3 percent compared to the case with no collars, respectively, and the reductions for a hole diameter of 0.2 (d/D) were 15.9, 24.8, 26.4, and 26.5%, respectively. Moreover, increasing the collar hole diameter (d/D) intensified scouring, such that an increase in diameter from 0.1 to 0.2 increased scouring by an average of 44.1 percent.

The present study has evaluated the efficiency of GARP model in forecasting the probability of gully erosion occurrence in Abgendi basin, Kohgiluye & Boyerahmad province. After field visits, 81 gullies were recorded by GPS and surveying camera, then the map of gully erosion distribution was prepared in ArcGIS environment. Variables of elevation, slope, slope direction, distance to road, distance to surface streams, land-use, pedology, lithology, drainage density and Topographic Wetness Index (TWI) were selected as the factors affecting the occurrence of gully erosion and used as independent variables in the modelling process. The modelling of gully erosion occurrence was accomplished using Desktop Garp software. Also, Receiver Operating Characteristic (ROC) and True Skill Statistic (TSS) were used for validation of the prediction results. The results indicated that, the most likely probability of gully erosion occurrence is concentrated in the central part of the basin, and it is reduced by moving towards the border parts especially southeast of the basin. Accuracy evaluation criteria ROC=0.97 and TSS=0.84 also indicate excellent performance of the GARP model in forecasting the probability of gully erosion in Abgendi basin.

The purpose of this study is to accurately measure the watershed potential for constructing rainwater harvesting structures. To carry out this research, the DEM digital-elevation model layer was used to prepare slope, hydrological soil groups and land use maps in the Arc GIS 10.3 software. The drainage density map was prepared by combining the DEM layer, topographic map, drainage density and hydrography data. A map of precipitation levels was prepared by using the pluvial method. CN map was prepared by combining land use and vegetation maps with hydrological soil groups. Runoff calculations were used to prepare runoff potential and coefficient maps. By combining them with the maps of drainage density, slope, and using analytical hierarchy process (AHP), a map of potential runoff production was prepared. The underground water fluctuation map was prepared using the base data and the water demand map was produced using (AHP). By combining this map with runoff production potential map, a water demand map was prepared. According to the obtained results, about 72 percent of the area has medium potential for the implementation of water extraction structures. It also shows about 22 percent of the area of low potential and about 6 precent of good potential.

The present review has been compiled to monitor management practices and hydrological response in 12 representatives and paired watersheds of the country including Tangeshol (Fars), Khamesan (Kurdistan), Dehgin (Hormozgan), Zidasht (Alborz), Shush (Khuzistan), Kakhk (Khorasan Razavi), Kechik (Golestan), Kasilian (Mazandaran), Gonbad (Hamedan), Goorband (Sistan & Baluchestan), Herris (East Azarbaijan), and Tahooneh (Yazd). For this purpose, about 161 studies were used and analyzed. Only 40 sources have specifically studied and compared the control and treatment watersheds. Therefore, it can be concluded that the applicability of the practices results and studies conducted in the paired watersheds have not been adequately described or documented. The first research was carried out in 2001 in Shush and Kasilian paired watersheds and most of them were observed in Kasilian (44 studies) and Kechik (28 studies) paired watersheds. The existence of the least research in Herris, Goorband, and Tahooneh watersheds (less than four studies) can be attributed to their new establishment and lack of extracted data. Most of the studies of paired watersheds in the country were related to the years 2015, 2016, and 2021 with 18, 17, and 17 cases.