نشریه هیدروژیومورفولوژی
پیاپی 35 (تابستان 1402)

Floods play an important role in the flow of rivers, so their investigation and analysis are importance. Studying the dynamics of floods and the water discharged into the sea (plume) is very important in the fields of fisheries, sedimentation, transportation and environment. Babolrud-River originates from the south of Babol city and flows into the Caspian-Sea after traveling about 67 kilometers. In this research, the expansion of the plume entering from the Babolrud-River to the Caspian Sea during the spring flood of 2018 has been investigated. For this purpose, firstly the images of Sentinel-2 satellite were taken, then the required pre-processing including geometric and radiometric correction was applied. According to the spectral behavior of muddy and clear waters, in the spectral range of wavelengths of 0.4 to 0.78 micrometers, this phenomenon can be distinguished. As a result, by using this feature and the optimal index factor (OIF), the best color combination with the largest information was detected. The combination bands of 3, 4 and 8, with the OIF of 0.19, was defined as the best band combination. In the next step, NDVI, NDFI, and MNDWI were applied, and thresholds were applied to the defined indices for better separation of muddy and clear waters. These thresholds were identified by drawing spectral profiles at the plume of river and checking their histograms. Finally, by building the decision tree with all these indicators and applying the thresholds, the amount of muddy water from the flood entering the Caspian Sea from the Babolrud-River was revealed.

In addition to damaging structural effects, earthquakes also have adverse environmental effects, including polluting water resources. In this article, the quality changes of surface water resources due to earthquakes are monitored. In the present research, in order to achieve the above goal, by using various data from Sunnynell 1 satellites, optical data from Landsat 8, and Madis satellite images, the data has been unified in such a way that they can be used together in the form of a dataset for processing. be placed In this research, by using the combination of satellite images (radar and optics), the Starfam algorithm, the spectral signature of Sentinel 1 data and the use of remote sensing indicators (MNDWI, NDVI and RGB color combination), water resources The studied area was identified and then the quality changes of surface water resources affected by the earthquake were obtained in the environment of ARC GIS and SNAP SANTINEL software. The results show that the earthquake caused shaking and displacement of the surface and subsurface layers of the earth and due to the karstic location of the studied area, it caused an increase in the concentration of dissolved anions and cations in water. In the studied area, the role of faults is very obvious. According to the geological structure of Zagros, Sarpol-Zahab city has numerous faults and the most changes of water resources are located in the main path of the faults and follow the fault lines of the region. Also, in terms of geology,

Underground dams can be a very suitable alternative to check dams so that in recent decades due to their privileged characteristics, they have attracted the attention of various researchers around the world. Geoelectric samples were carried out at the axle and reservoir of Dehbakri underground dam by sondage putting method and with using Schlumberge array. These samples were performed during 6 profiles (P1 to P6) and 32 electric sondage. The results of geoelectric studies indicate that there is a two-layer model along the geoelectric sections that the upper layer has alluvial and the underlying layer has bedrock. Alluvial layer is divided into dry parts at the top and wet parts at the bottom. The depth of reaching groundwater level varies in different parts of the study area, but on average it can be considered 5 meters. Alluvial thickness also varies during profiles, but the highest thickness is generally in the middle parts of the geoelectric sections and more close to the right support. The highest alluvial thickness was estimated at the S26 catheter site and 13 meters. Considering the specific electrical resistance scale of the layers and considering the rock outcrops on both sides of the river, it seems that the bedrock in most places has alternating lithology made of shale, marl and sandstone and in some parts of the marl material.

Today, soil erosion is one of the important problems in catchments, lakes behind the dam, various agricultural areas and natural resources, which also causes land degradation, reduced soil fertility and filling the reservoir of dams. Due to climatic conditions, the erosion process in Iran requires more attention because in this country, soil formation occurs in the long run and its destruction in the short term. The best place to control soil erosion is catchments. It is necessary to pay attention to catchments in the erosion process, especially catchments whose rivers flow into lakes behind dams or play an important role in providing drinking water to a city or region. In this study, using the hydrophysical model (CSY), the sedimentation potential of Damghan River watershed in the southern slopes of Alborz was calculated. The results of this study showed that the Namakeh sub-basin has the highest and the Dibaj sub-basin has the lowest sedimentation potential. The Kalateh Rudbar basin is also in moderate conditions. Therefore, the Namakeh basin is more vulnerable to erosion and should be properly managed by implementing soil protection plans and proper management of the erosion process in this basin.

The studied area on the Haraz Road from Poldakhter to Vana is prone to avalanches due to its cold mountain climate. The purpose of this research is to determine the most important factors affecting the occurrence of avalanches and its risk zoning using LNRF and Shannon Entropy models. For this purpose, the criteria of snow cover, elevation, slope, aspect, slope curvature, landuse and distance from the road have been used. The results of determining the most important factors affecting the occurrence of avalanches in the studied area using Shannon's Entropy model showed that the aspect, landuse, distance from the road and snow cover with weights of 0.541, 0.143, 0.129 and 0.083 respectively are more important. Avalanche risk zoning maps show that the highest avalanche risk is due to the location of these areas at an altitude of 2100-2700 meters and a slope of 30-60 degrees with the direction of the northeastern and northern slopes. Evaluation of avalanche risk zoning maps using the empirical probability index (P) indicates the appropriateness of Shannon entropy and LNRF models in the region, but the application of Shannon entropy has led to an increase in map accuracy up to 97%.

In Iran, due to the fact that a large part of the country is located in arid and semi-arid areas, the problem of salinity has become a big problem in agriculture. In Iran, about 14.7% of the total area of the country is made up of saline lands, and nearly 50% of the agricultural lands are faced with the problem of salinity or alkalinity and waterlogging to varying degrees (Hussaini, 2015). In the Azerbaijan region due to Lake Urmia, and illegal cultivation and extraction of underground water, soil salinity has become a big problem in a large part of the region and it seems that its dimensions will increase in the future. In this article, the most research focus is on the problem of salinity. The soil is within a radius of a few kilometers from Lake Urmia and near Tabriz. Preliminary observations and studies show that the problem of water salinity and then soil salinity has increased in the study area to such an extent that it has caused farmers to complain and abandon agriculture. and in terms of the dangerous dimensions of the problem, it has drawn the attention of researchers to the problem of soil salinity. The main reason for focusing on this area is excessive soil salinity within a 50-kilometer radius of Urmia Lake.

In recent years, the irreversible phenomenon of land subsidence has led to environmental hazards in various plains of Iran including Gorgan. In general, the most important activities causing this phenomenon are inappropriate groundwater withdrawal and geological factors. The research method consists of two sections: identifying subsidence areas and examining the effective factors and parameters and evaluating the impact of each. In identification section, radar interferometry technique was used to compare the phase taken from two radar sets from the same region at two different times and measurement of land surface changes over time can be achieved through interferogram, and in the effective factors analyzing section, the determination and analysis of effective parameters such as water level drop, texture and thickness of soil layers, especially fine-grained layers were investigated. The results of the satellite data analysis indicate that the region is steadily subsiding. The mean velocity map along the satellite line of sight obtained from time series analysis showed a subsidence rate of 14 mm / month (169 mm / year). The identified subsidence range is approximately eastern-western which is consistent with trends in structures such as the Caspian. Figures of water level and precipitation in this area during 2007 to 2009 show a decreasing trend despite of seasonal fluctuations, and analysis of effective parameters shows that the subsidence is due to the same drop in water level or the difference of same thickness of the fine-grained layer at different depths

The damming can cause changes in the hydrological regime of the river. There is a crucial need to understand the potential impacts of water structures on river hydrologic regimes in order to set managed environmental flows. In this study, the statistics of Tang Esferjan hydrometric station at the outlet of Hoonejan watershed (Isfahan province) were used to investigate the monthly average discharge and flow duration curve alteration using IHA software (version 7.1). The amount of monthly flow has decreased in the post impact compared to the pre impact period. The flow duration curve is higher in all seasons before the construction of check-dams than after construction. The interpretation of flow duration curves shows the reducing effect of correction clauses in all types of flow. The hydrological indicators of the stream (normal discharge index in the high flow condition, normal discharge index in the low flow condition and normal discharge index) have decreased in the post-impact period compared to the pre-impact period. In all months of the year, except for February, March and April, the rate of decrease of the normal discharge index in the low flow condition (Q75) was higher than the normal discharge index in the high flow condition (Q25). The normal discharge index in the high flow condition has decreased more in the spring season than in other seasons after damming. The normal discharge index in the low flow condition in winter, autumn (91%) and summer (90%) has decreased more than in spring.