جستجوی مقالات مرتبط با کلیدواژه "bashar river" در نشریات گروه "جغرافیا"

Investigation of River Meanders Geomorphologic Changes Using Satellite Imagery During the Period from 1990 to 2018 (Case Study: Bashar River) Introduction Identification of the shape and structure of the river is called the river morphology so that it can be obtained by knowing the river morphology. The morphology of a river is affected by different factors such as the rate of erosion and sedimentation. In river morphology studies, information such as geometric shape of the river, shape of bed and longitudinal river profiles can be obtained. The most common criteria related to river morphology are geometric or River Plan Rivers are one of the main sources of water and energy for human beings Bashar River is one of the branches of the Khorsan River and flows in the city of Yasuj and part of the city of Sepidan in Fars province. This basin, with geographical coordinates of 30 °, 15 ° to 30 °, 50 ° north, and 51 °, and 25 ° to 51 ° and 48 ° east, collecting waters of this highland area and entering the Khersan River. The Bashar River, about 150 km long, originates from the western slopes of the Zagros Mountains, whose early branches are located in the northwest mountains of Sepidan, Fars province, and flows along the southwest to the northwest. The area of Bashar basin is 3099 square kilometers and its maximum height is from the height of Yasouj 4283 meters and the minimum height is 1320 meters.

To identify the hydraulic and morphological characteristics of the rivers, the quantitative geometric parameters of the river are measured and calculated. In the study of Meanders to determine the behavioral pattern of the river and how it changes over time, the Cornish method and river pattern recognition through satellite images have been used. In order to obtain the river wavelength on the river plan, the ArcGIS software first defined the curvature routing points of the river, and then the two points indicated by a single segment are connected, the length of this segment can be calculated in the ArcGIS environment. Remote sensing technology has a higher position in tracking river changes than other methods of study, because in most cases it is not possible to study the field for us, or it is too time consuming or costly, or to have authentic historical documents available to us. In order to determine the variation of the Bashar River route by using distances, the satellite images of the area were first obtained and processed using ENVI software. For this purpose, after the digitization, the study area was cut and the Flaash method of atmospheric correction was applied to the images. In the next step, for the overall understanding of the unregistered classification area, the method was K-means or C-means. Then, for the classification of the oversight, using the classes constructed by ROI, Maximum Likelihood is one of the most accurate and most used monitoring method. ArcGIS software was called to determine the amount of image changes. A binary method was used to isolate water pixels in the images. To determine the maximum river change, the buffer was 100 meters along the route. The Thaning method was then used to separate the river from other parts of the water.

By measuring the central angles of the Meanders in AutoCAD software, their information and specifications were calculated and the number of river meanders from the source to the end was determined. Then, using the Cornish method, the central angle of each meander is calculated and by predicting the extent of development of each grunge, the menders that have a high potential for interruption in the future can be predicted. According to the information obtained from the Meanders of the Bashar River, the Meanders are categorized and identified using the GIS software, according to their type of route. They are divided into four simple, direct, composite, and arterial meanders. Euclidean distance was measured in different parts of the river that was more distorted and more variable in order to determine the extent of the river route changes and which period of erosion occurred. So, to calculate the Euclidean size, at first, where the river route had a large difference, two points were measured and the distance difference was measured, and then the coordinate system was determined. Then, in Excel, the difference between the two points was calculated and the corresponding graph is drawn which shows the distance and the amount of path changes in two years. In this area, from both directions of the river in 1990 and 2018, about 40 points were taken at an approximate distance of 3.5 km, and the difference between these two points was measured and plotted. Conclusion One of the main goals of this study was to investigate the changes in the bedding of the Bashar River. The results show the potential of the river to produce morphological changes in different sections of the river route, so that Figure 14 shows the river route changes during the period from 1990 to 2018, indicating that about 62% of the route is displaced and Changes have been made. According to the results, the role of human in the creation of Meander was determined by analyzing the river route. Meanders, along with human activities, such as agriculture with change in use and construction or harvesting of sand, had the most displacement. It can almost be said that along the river's route, it is rarely seen that it has not been used by humans. The results show that the extraction of the Bashar River route using satellite imagery to determine the river boundary has a high potential in analyzing geomorphology and identifying changes and the river is moving. The study of river bed changes using remote sensing analysis revealed that the basin of the Bashar River during the statistical period (2018-1990) was about 38% unchanged and 62% affected by various factors.

Rivers are unstable environments which under the natural and human factors influence, change their direction and pattern. These changes are not the same in all parts of the river, and depending on the factors affecting it, occurs the different levels of change. The study area is part of the Bashar river which contains three intervals between nations Blvd. Yasouj to that part of the river town Mithraian welding is an interval. The purpose of this study is investigating and detecting river bed geometry changes in the period being studied. In this study, the factors affecting on river bed geometry changes and the rate of change and its impact on development of the Yasooj were investigated. The method of this research is a comparative analysis which using direct and indirect observations and images and maps, the type and extent of geometry changes in waterways is studied and between the four periods, and four spatial interval is analyzed.
Also, the 1335 aerial photography, 1362 aerial photography, images of IRS in 1384 and 1393 Google earth images have been used. Accordingly, the riverbed in four periods digitalized in Arc Gis. And then, the riverbed changes, and river location displacement in the river examined in each period, and every four intervals.The results of the data analysis, satellite imagery and aerial photographs indicated that River beach in the study area has been relocating. According to data the first period and the fourth period variability is greater than the other intervals. During the surveyed period at intervals of choice for the most influential factor in changes in morphology, land use, geology and tectonics of the track bed had been. As a result, any type of urban development around the river requires River changes management in the intervals being studied.

River bank erosion is one of the major sources of sediment for many rivers around the world. The aim of this study was to identify erodible riches in Bashar river because the role of this river's in development of Kohgiluyeh and Boyerahmad province. In this study, using Satellite imagery, aerial photos and field survey from 1975 to 2015, the riverbank migration patterns for period of 40 years were investigated. After creating database of recorded data Bashar river, bank lines in different years digitized. Then, by comparing successive changes in bank line position, patterns of erosion and accretion was determined. Due to dischargr and Geological factores effectes on river pattern, these factors were evaluated. The Result of for identify erodible riches in Bashar river using GPS and field surveys, verified. The area of bank erosion and accretion by comparing sequential changes in banklines position determined. For short-term analysis, the migration rate from one any image to the next image is estimated. For long-term analysis, the migration rates are based on the difference between the 1975 image as the reference, and subsequent images. The results indicate that the erosion– accretion patterns in the sub aerial and subaqueous areas of the beshar river have changed significantly since 1994. For the short-term analysis, the highest erosion and accretion amounts are 4.7 and 7 ha from 1975-1984 and 1984-1990, respectively. the lowest erosion and accretion amounts are 2.6 and 2.3 ha from 2008-2011, respectively. The highest rate of bank erosion in different reaches equal to 9.6 and 4.6 ha/y in reachs of fifth and second bserverd. Also rate of bank accretion in fifth and second reachs equal to 9.6 and 4.6 ha/y observerd. the lowest erosion and accretion rate in reach of seven equaled 11.7 and 6.4 ha/y accounted, respectively. The correlation coefficient the between erosion and discharge and annual discharge averagelly for the short-term analysis observed 0.54 and 0.44, respectively.

Among the various environmental hazards, flood is the greatest and most important climate crisis which takes every year the lives of thousands people and impose severe damages on human society and environment. Today, it is clear that controlling all hazards, including floods is not possible. Suitable management can only minimize the damages. The literature on natural disasters management indicated that in the process of natural disaster management and their vulnerability mitigation, there are two dominant paradigm: technic-based approach and community-based approach.
Community-based approach welcome the local cooperation and participation in disaster management process and calls for strengthening local capacity through the participation of all individuals and groups at the local level. This approach is not only appropriate to provide solutions for disaster reduction, but build disaster preparedness. Because disaster preparedness planning requires special attention to local participation. In the geographic area of Bashar River Basin, due to the lack of suitable agricultural land and greater quantity of water for rice crop, villages have been built at rivers edge. So that, most of the houses and farms in the villages are located very close to the river. However, these locations are extremely vulnerable to flooding. This study reviews the status of local participation and its impact on reducing flood risks. Also, this research focuses on factors influencing local community trends and choices in the participation rate.
This study is applied research in terms of purpose and uses descriptive-analytical method. According to the nature of the study, data were collected through fieldwork and library research methods using observation, interview, questionnaire and evaluation card techniques. To understand different characteristics of community, Likert scale and one-sample t-test were used and measurement scale for data was ordinal. Also. The method of selective experimental approach based on profit was taken to evaluate the level of different trends in Community's financial participation for reducing detrimental effects of flood. To recognize the community awareness and perception toward flood risk and the probability of its occurrence in the future, the willingness level to participation and to explore the effective factors on villager’s decisions and to utilize modern management techniques the selective experimental approach based on evaluation card and logit model were employed.
The results of statistical analysis showed that in the study area, 86.5% of the community have experienced the damages caused by flooding and forecasted the likelihood of heightened chance of flooding in the future. Finding showed that although the people use traditional methods for managing flood, but they tend to employ modern methods such as dam building for reducing flood risk. This help them to increase the safety factor for their locations and farm lands. In spite of the fact that the villagers expressed the higher safety factor for new management methods such as (dam building, river broadening and preventing the destruction of forest and environment), but it seems that improper functioning, adverse consequences (environmental and socio-economic) of projects implementation (dam building) as well as the inability of villager's financial participation (high cost of this kind of methods), are barriers to using them for lowering the flood risks and damages.
The review of the possible role of some intervening variables to predict local communitie's participation in decision-making processes showed that low-income, old age of the samples with high average (47.61) and education with lower average (3.16) are the most important factors influencing community decision making. The results of binominal logit model showed that the proposed variables is significant at the 5% level. If the offer price increase, the chance of resident's acceptance of participation will decrease and vice versa.