عنوان مقاله [English]
Rivers are generally diverse ecosystems characterized by significant habitat heterogeneity. These heterogeneities depend on the activity of river geomorphic processes (Cohen et al., 2016, 528). In recent years, floods in rivers have caused great damage to human society. Morphometric factors of the river and its environments and predicting future conditions can be effective and necessary in planning and landscaping of riverside areas (Masoumi et al., 1400, 638). Rivers and canals are a completely dynamic system, and their location, shape, and other morphological characteristics change continuously over time. Factors such as geological, geomorphological, hydrological, land use change and destruction of natural resources of rivers are subject to change (Yasi, 2009, 27). It is one of the main assets of a water nation that currently flows in the rivers of that country and due to its role in locating and expanding settlements and cities, roads and agriculture, rivers have been of great importance in the past, so that from the beginning of progress And the development of human societies have shown their place in every stage of human civilization. For this reason, river systems as one of the most vital elements of the earth's surface, have been considered by humans from various aspects (Yamani et al., 2003: 63). Meanwhile, humans, along with morphogenesis activities, change the face of the earth by changing land use, destroying natural resources, plowing the land in the direction of slope, planting trees in riverbeds. , Using remote sensing and GIS approaches. They calculated the amount of increase and change in erosion in one open using Landsat time series optical images and concluded that the factors of hydraulic flow regime, upstream land use, natural canal slope and vegetation around the canal had the greatest impact on these changes. This study seeks to evaluate and analyze the morphological changes of Kahman River, using the fitting of tangent circles and the reason for the formation of torsions at different intervals from the perspective of applied geomorphology.
In this study, geological maps at a scale of 1: 100000 of the Geological Survey, topographic maps at a scale of 1: 50,000 digits of the Geographical Organization of the Armed Forces, satellite images of Landsat 8 pass 166 rows 37 dated 16 April 2017, Landsat 7 pass 16 rows 37 September 2013, Landsat 5 pass 16 Row 37 November 2001, Climatic data of the study area, including temperature and precipitation, which were used by the Meteorological Organization of Lorestan Province and a 30-meter digital elevation model of the study area to investigate the geological features, topography and extraction of waterways. ArcGIS software was used to create the database, spatial-spatial analysis, and ENVI software was used to process satellite images. To do this research, the Landsat TM satellite sensor images for the years 2001, 2013, 2017 were first downloaded. To correct the geometric and radiometric errors of these images, geometric and radiometric corrections were performed on these images using ENVI software. The Kahman River route was digitized in the ArcGIS software environment during the mentioned years. The output of this work was prepared in AutoCAD format. Then, in AutoCAD environment, in order to quantify the development rate of Kahman river inlet and determine its changes over time by fitting circles tangent to the arc, the geometric parameters of the river including canal length, canal length, curvature coefficient and river length using the tools available in AutoCAD software measurement and morphological changes of the river were reviewed.
In order to approach this study, after preparing the images related to 2001, 2013, 2017, geometric and radiometric corrections were made on these images using ENVI software and geometric and radiometric errors were eliminated. Then the river route in all three time periods on these images in digital ArcGIS software environment and output in AutoCAD format was provided. In the AutoCAD software environment, using the available tools, circles were fitted on the river arches with the utmost precision. The digitized path on satellite images shows that the morphology of the Kahman River in 2017 has changed more than in 2001 and 2013 (Figure 3). The tangent circles on the arches of Kahman River, the turning points of the arches were determined and in AutoCAD software environment using existing tools, the geometric parameters of canal length, canal length and river length were measured and by placing this information in equation (1), the curvature coefficient was calculated. (2). In addition to other statistical parameters including mean, standard deviation, coefficient of variation, minimum and maximum geometric parameters of waterway length and waterway valley length, for analysis in Excel software environment, the information obtained from Table (3) shows that the total length of the river, In 2001 it increased from 36,217 meters to 38,620 meters in 2017. The curvature coefficient has also changed from 1.136 in 2001 to 1.767 in 2017. The number of arches has increased from 37 arches in 2001 to 55 arches in 2017. In other words, the length of the river, the number of arches and the curvature coefficient have been increasing. However, the length of waterways and the length of valleys of similar waterways (in the range of measured arcs) have decreased in the period 2001 to 2017. From this information, it can be seen that in the period from 2001 to 2017, the number of arches increased, but the distance between the two ends of the arches decreased, or in other words, the length of the canal valley decreased. On the other hand, increasing the number of meanders has increased the overall length of the river
Destruction of vegetation, destruction of forests and pastures, change of use from agriculture to housing and plowing the land in the direction of the slope, etc., increase the severity of erosion, prevent the infiltration of water into the soil and increase runoff. For nearly a decade, the residents of the study area have attempted to change the unauthorized use and encroach on the river area (construction and planting trees in the riverbed) Figure (5). They have also invaded the most pristine mountains in the basin (Green) and looted the dominant plant species in the area (shallots that have roots and prevent soil erosion) for sale. Since this plant species is almost endangered due to savage looting, these individuals attack tree and shrub species such as oak, argon, etc. and cut each of them for a specific use (Figure 6). Based on the information obtained from statistical indicators, the calculated geometric parameters of Kahman River (Table 2), the average curvature coefficient has increased from 1.136 in 2001 to 1.377 in 2013 and 1.767 in 2017. The results of the analysis of this index with reference to Table No. (1) show that the Kahman River was sinusoidal in the period 2001 to 2013 and changed to Pichanrud in the period 2013 to 2017.
Keywords: "Seismicity", "Watershed", "Geomorphic features", "Topraqi pot", "Neotectonic".