نشریه هیدروژیومورفولوژی
پیاپی 37 (زمستان 1402)

The aim of this study is to estimate the rate of soil erosion and its relationship with landforms of Zonuzchay catchment in Marand city. In this study to estimate the rate of soil erosion and sediment production, the modified global model of soil loss (RUSEL), geographic information system (GIS) and remote sensing (RS) was used. To implement the model, rainfall erosivity factors (R), soil erodibility factor (K), slope length-gradient factor (LS), support practice factor (P), and cover-management factor (C) in Arc GIS environment calculated and Then a soil erosion map was drawn. Topographic position index (TPI) was used to classify and map the landforms of the basin. Then, the role of different landforms in relation to soil erosion rates was investigated by combining relevant maps. The results showed that the values of soil erosion in Zonuzchay basin vary between 0 and 50.20 tons per hectare per year. Valleys and cuts located on heights and slopes have the highest rate of erosion and low-slope domains and flat areas and plains include areas with low and very low erosion. In Zonuzchay basin, soil erosion is mostly on the builders of Flysch type deposits, red and gray conglomerates with Marny layers and alluvial terraces. Investigation of regression relationships between (RUSLE) model factors and soil erosion of Zonuzchay basin showed that the slope length-gradient factor has the greatest effect in calculating the rate of erosion of Zonuzchay basin. .

Rivers are very important in terms of human uses and ecological functions. In the present research, the environmental flow components of the Khiavchai River have been determined. Therefore, changes in the EFCs were determined using IHA software. According to the results, the values of low flows were high in the first period (1988 to 2017), but decreased in recent periods. Also, the decrease in the discharge values of the maximum flow indicators and the increase in the number of days with zero discharge to the number of 174 days were also caused by the change of the river regime. The amount of peak rate and decline rate components has increased in recent periods. The values of low flow duration indicators and low flow frequency have increased. Based on the change of flow dispersion index, the occurrence of strong or very low flows in the river has been intensified. According to the FDCs, in the early periods of the river flow regime, river flow was higher than 0.01cms during the year, while in recent periods it has decreased to less than 0.001cms. Based on the changes in the duration of the flow in recent periods, the duration of the river has changed to 50-60% of the days of the year with a very low discharge. Overuse of river flow changes in the flow regime, and successive droughts have increased the severity of the change in the flow regime and the deviation of the river conditions from the normal state.

Terraces are important archives for paleontology. In this research, the paleotemperature changes and discharge frequency of Jajroud basin in the northeast of Tehran have been investigated based on the sedimentology and geochemistry characteristics of the reservoirs. First, the sediment samples were analyzed with calcimetry, EC, XRF, and PH techniques, and then these data were correlated with the indices of salinity, chemical weathering, acidity, and maturity of the sedimentary layers of the defenses. The results show three periods of flow changes, during the alternation of cold and warm periods of the river. One is at the peak of the glacial period, when the accumulation of snow and ice in the mountainous part has reduced the discharge (before the Holocene). In the second stage, by passing from the glacial period to the warm period (11 to 8 thousand years ago), Jajrud has experienced its highest discharge. Because the melting of glaciers has been accompanied by rainfall. The existence of very coarse layering in the early Holocene terraces indicates the occurrence of floods in this period. In the third stage, the dominance of recent hot and dry conditions (8 thousand years ago until now) and the lack of glacial deposits have led to a decrease in river flow. Based on this, the geochemical studies of the reservoirs can provide valuable data to recover the dynamic changes of flow and discharge during the Quaternary period and can be generalized to other similar basins.

In this researchlandslide sensitivity was zoned using statistical models intheKurdistan Dam watershed and the most appropriatemodel was introduced.First, the studied area was determined and with field observations, the number of 9 landslides was recorded and a landslide distribution map was prepared. In the next step, the factors affecting the occurrence of landslides including geology, rainfall, land use, distance from the river, distance from the fault, slope and height were identified and then a map of these factors was prepared. To determine the rateof each of the effective factors in the occurrence of landslides, the map of each information layer of the effective factors is integrated with the distribution map of the landslide and using AHP, BWM and FUCOM statistical modelsseparate information layers are weighted and By overlapping different layers, the final landsliderisk zoning mapswere prepared and compared.The results showed that land use in AHP and BWM methods and rainfall lines, in addition to land use inFUCOM method have the greatest effect and the criteria of heightdistance from the fault and slope respectively in the three AHP, BWM and FUCOM methods have the least effect on the occurrence of landslidestheresults showed that the lithological variable has a great role on the occurrenceof landslides in the studied area.In generalthe results showed that in AHP and BWM methods, the numberof required pairwise comparisons increases significantly with the number of compared parameters, and in this case, the uncertaintyof opinions increases, which shows the superiority of the FUCOM method over It showswell in other ways.

Fractal dimension is a powerful and important index that reflects the physical and morphological characteristics of rivers and has a close relationship with geometric features of rivers. The fractal pattern was used to investigate the sinuosity of the Gharehsou River in Ardabil Province, using the box-counting method. The results show that the fractal dimension of the Gharehsou River varies between 2.068 and 2.186. The minimum fractal dimension is in the first category of meanders with lower areas of tangent circle, and the maximum number of circles falls into the eighth category (having high areas of tangent circle). Based on the correlation between the number and area of tangent circles (0.71 to 0.84), it can be said that the river reaches studied follow a fractal and self-similar pattern. The fractal dimension values in the Anzab village-Taleb Qeshlaqi village reach were calculated to be 2.23, indicating a higher level of self-similarity, which is related with the naturalness of this river reach, which is located within a plain area, and the river has undergone more evolution. On the other hand, in the Taleb Qeshlaqi village-Sabalān Dam reach, the fractal dimension value was found to be 1.85, which may be related to the river traversing steeper paths, limiting its meander development and making the fractal pattern less observable. Human interventions in the river's course, as well as the river's passage through agricultural lands in some cases, have led to changes in the width and depth of the river and restrictions on meander expansion.

This study investigated the trend of hydroclimate parameters of the Miankaleh wetland using the Mann-Kendall test and Sen slope estimator. Temperature, precipitation, and evaporation parameters were used from the synoptic stations . Also, the discharge data were used from the hydrometric stations of Khalil Mahalleh, Tazeh Abad, Baghoo, and Vatana stations. The results of the Mann-Kendall test showed that the temperature in the Dashte-Naz station in spring and summer seasons has a significant increasing trend with 95% confidence and a significant decreasing trend in winter. Also, there is an increasing trend in Hashem Abad station, with a 95% confidence level in the spring and autumn seasons. Precipitation in Dashte-Naz station with a 95% confidence level has a decreasing and increasing trend, respectively. The most frequent trend changes in Dubai are related to Vatana station, which has a decreasing trend on an annual scale. Evaporation in Dashte-Naz station has a decreasing trend in the autumn and winter seasons and has an increasing trend in spring. Also, in Hashem Abad station, the evaporation rate in autumn has a decreasing trend. The Sen slope estimator method results showed that precipitation in Dashte-Naz station in December was -2.983, and on the annual scale, it is related to Hashem Abad station with -6.283. The highest monthly positive trend line slope of all parameters is related to August precipitation in Dashte- Naz station with a value of 3.20, and the highest annual scale is related to evaporation in Hashem Abad station with a value of 2.157.

In global meteorological literature, atmospheric rivers are defined as long and narrow pathways of intense water vapor transport towards the polar regions in the middle latitudes, typically associated with low-level jet streams along the leading edge of extratropical cyclones. In this study, to identify the origins of the incoming atmospheric rivers to the study area, precipitation systems that occurred at more than half of the region's stations were selected. Then, using vertically integrated water vapor flux data from the east and north of the study area with a spatial resolution of 0.5 x 0.5 degrees, the magnitude of the water vapor flux was calculated. To calculate the magnitude of the flux, data including specific humidity and meridional and zonal winds at pressure levels from 1000 to 300 hPa were used. showed that these rivers have entered northwest and west of Iran from four moisture sources. The sources are the warm southern seas (the Sudan - Red Sea low-pressure pattern), the convergence zone region, the combined source of the Sudan low-pressure system and the Mediterranean circulation, and the Mediterranean Sea. Among these sources, the warm seas of Arabia and Oman and the Red Sea had the largest share in the incoming rivers to the region. These atmospheric rivers have been the strongest in terms of both temporal continuity and moisture flux. They first enter southwest Iran and then into the study area. The atmospheric rivers with the convergence zone source rank second in terms of their contribution to the region's precipitation.

Considering the importance of the subject, in this research, the factors affecting the hydrological changes of the Taleghan River have been investigated. Descriptive-analytical methods have been used in this research. The most important data of the research included Landsat 5 and 8 satellite images, the SRTM 30-meter height digital model, Taleghan synoptic station climate information, and regional discharge information. Also, the most important tools used in the research were ArcGIS, ENVI, and SPSS. According to the subject of the study, this research has been done in several stages. In the first stage, the evaluation of land use changes, in the second stage, the evaluation of changes in climatic elements, and in the third stage, using IHA indicators, has been paid to evaluate the hydrological changes of the Taleghan River. The results of this research have shown that during the years 2000-2017, the average temperature of the region has increased and the area covered by snow has decreased. Also, under the influence of population growth, the use of artificial areas has increased and the use of gardens and pastures has decreased. Also, the total results of this research have shown that the discharge of the Taleghan River under the influence of natural and human changes, in terms of all IHA indicators, has had a significant decreasing trend. Also, among the stations in the region, the Glink station, which is located downstream of other stations, has faced more changes, which can be considered as the result of human activities and climate changes.