مجله علوم و مهندسی آبخیزداری ایران
پیاپی 53 (تابستان 1400)

Today population growth, inaccurate management practices and land degradation processes have caused many watersheds to be severely degraded, leading to increased runoff and sediment. In this study, the aim of the study was to investigate the effect of land use change on surface water fluctuations in the Doiraj watershed. Landsat satellite imagery was used for three periods of 1995, 2006, and 2015, it was found that the major changes occurred with decreasing forest and rangelang  levels and increasing land barren. For modeling rainfall-runoff, a SWAT computer model was used. Then, using the SWAT_CUP model, The performance of the model was evaluated using statistics, NS, R2, P_FACTOR and R_FACTOR. After calibration and validation, the values of these coefficients were 0.58, 0.60, 0.81, 0.87 for the calibration period and 0.56, 0.57, 0.81 and 89 for the validation period of the model, respectively was obtained. Annual runoff estimation indicated that changes in forest, pasture and wasteland land use from 1995 to 2015 increased the outflow runoff the basin from 3.91 to 5.85 m3 / s.

Landslides are one of the most destructive phenomena of nature that cause damage to both property and life every year, therefore, landslide susceptibility zonation is necessary for planning future developmental activities. In this study, the operator of fuzzy logic in landslide hazard zonation has been used in ArcGIS software environment in the southern and northern slopes of Binalood mountain range in Khorasan Razavi province. For this purpose, first layers of 20 factors related to the occurrence of landslide phenomenon were prepared. After fuzzyizing the layers in the ArcGIS environment, the landslide risk zoning was performed using fuzzy Product, fuzzy sum, gamma 0.8 and 0.9. Finally, the accuracy of the obtained maps was evaluated using ROC curve and landslide distribution map. Evaluation of landslide zoning results showed that Fuuzy product and fuzzy Sum operators due to their high and very low sensitivity are not suitable for landslide risk zoning. But fuzzy gamma-ray operation is suitable for landslide zonation. According to the results of the ROC curve and the landslide distribution map, the gamma operators (0.8 and 0.9) have the best performance in modeling and zoning the landslide risk. According to the Landslide Risk Zoning Map using Gamma 0.8, about 72.4 percent of the area has low and very low sensitivity, 9.8 percent has high and very high sensitivity and 17.8 percent has moderate sensitivity.

Flood damage assessment is often necessary for early flood management. To this end, this paper provides a framework of rapid estimation of flood damage and identification the flooded areas in March 2020 using Sentinel-1 satellite data. To this end, in the present study, after applying the necessary pre-processing in SNAP6 software, the backscattering coefficient, or sigma naught for two images related to before and after the flood occurrence was extracted. The backscattering coefficient histogram was used to separate the image into two classes including water and non-water and the threshold of 0.01 was obtained based on it. Then, by applying mathematical operations on both backscattering images, the binary image of water and non-water was prepared and the flooded areas were determined based on the difference between the two images. After detecting the flooded areas, Sentinel images were classified into three classes including waterbody before flood, flooded area and other lands using supervised classification algorithms. The results indicated the high accuracy of the Random Forest algorithm with kappa of 0.92 compared to other algorithms. By overlaying the land use and flooded areas maps, the inundation percentage for each land use was determined. According to the results, bare lands with 27.9 percent, residential land with 16 percent and rangelands with 12 percent had the highest inundation percentage, respectively.

In this study, plant samples were identified using available scientific sources and by examining various plant characteristics including: density, frequency, canopy status, roots and rhizomes, amount of litter produced, vegetative form, propagation method and longevity, priority plants were classified in order to stabilize and protect the marls. According to the results, 34, 59 and 61 species, respectively, in the first to third priority in order to stabilize and conservation marls in these watershed were introduced. It is necessary to reproduce and establish bush, shrub, tree, forb and perennial grass species, and annual grass and forb species in these lands, respectively. Also, considering the botanical characteristics and natural characteristics of the region and emphasizing that in addition to the issue of erodibility and sediment production, marl lands are mainly low permeability and insufficient moisture for the establishment and growth of plants; It is recommended for the establishment and reproduction of species such as: Astragalus susianus Boiss.، Astragalus gossypinus Fisch. and Artemisia Aucheri Boiss. Take action in the areas covered by marl in this watershed. Because with the management and establishment of these species, in addition to soil conservation, the opportunity to reproduce and preserve these valuable plant species will be provided.

The present study investigated the effect of guar biopolymer on soil wind erosion. Assuming that Guar gum can control wind erosion, its ability to reduce soil wind erosion was examined by wind tunnel tests. Examined soil samples were gathered from sandy hills of Segzi plain, located in Isfahan Province. Then were prepared in plates with diameter of 23 cm treated with guar gum suspension so that 0.2, 0.4, 0.8, 1 and 1.2 gr of the biopolymer were scattered per square meter of sample surface. Wind tunnel tests were performed on samples at speed of 7 m/s to 15 m/s. The test results indicated that the resistant crust formed on soil surface due to spraying Guar suspension can highly increase soil resistance to wind erosion. 1.2 gr/m2 of Guar can reduce erosion up to 98 percent. Soil sieving analysis results pointed out that Guar gum causes enlargement of the soil aggregates and so in reduction of erosion and raise in threshold wind velocity from 7 to 10 m/s. Thus, using Guar gum can be considered as a suitable method for controlling soil wind erosion, after the field experiments.

In the present study, the phenomenon of dust and the annual and seasonal trends were studied in Golestan province over a period of 18 years (2000-2017). According to the tools and techniques of Remote Sensing and wind dust diagrams, the dust phenomenon was studied. In order to investigate the occurrence of dust, AOD related to MODIS sensor was used. The results show that the highest annual average of AOD (equivalent to 0.321) was indicated in the year 2009 which shows the highest intensity and concentration of dust. Also, in terms of seasonal changes, autumn and winter seasons have a small share of dust concentration. The highest dust concentration in Golestan province is related to summer and especially July. Also, the seasonal wind dust diagrams show that the dust direction is mostly from west and southwest and the role of north winds in dust production is negligible. This result shows that contrary to popular belief that the source of foreign dust in the province is often Turkmenistan, the role of Turkmenistan in the Golestan dust production is small and the dust mass has entered to Iran from the west and from the northern parts of the country to Golestan province.