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• A GIS-based study on the changing course of the River Jiadhal in the Dhemaji district, India

  14-27

  Pranamee Gogoi

  Views:

  54

  River bank-erosion, deposition and channel-shifting are considered most dynamic and significant geomorphological processes formed by complex geological, hydrological, and anthropogenic factors. In the present study, river Jiadhal is one of the main sub-tributary of the River Brahmaputra in the Dhemaji district of Assam that changes its channel course frequently due to bank-erosion and sediment-deposition in the intermediate part and lower course of the channel. A study on the changing course of the river Jiadhal was carried out using satellite imageries for the years 1987, 1997, 2007 and 2017. The study found that the changes in the river vary from time to time and the bank-erosion and sediment-deposition fluctuate from place to place.  The total area of bank-erosion is 13.34 km² from 1987 to 2017 and the total area of sediment-deposition is 14.59 km² from 1987 to 2017. This paper evaluates how the shape, size and position of the Jiadhal River have changed from the years 1987 to 2017 using remote sensing and GIS techniques. The study is also necessary for effective management along the side of the river Jiadhal to control bank erosion and to mitigate the adverse impact of erosion and channel-shifting. 

• Morphometric changes of the River Bodrog from the late 18th century to 2006

  28-40

  Nikoletta Mecser

  Gábor Demeter

  Gergely Szabó

  Views:

  38

  The river regulations of the 19th century have affected each of our rivers to a different degree. In the case of the River Bodrog it was stronger than the average. In our paper a section of the river between Bodroghalász and Szegi was examined, the extent and intensity of river channel changes was intended to be determined. The applied series of maps and aerial photos was georeferred and the river channel was vectorized. The morphometric parameters of the channel were measured and the changes were evaluated using the created database. From methodological aspect we concluded that the 9 variables can be grouped into 3 factors therefore most of the indexes can be substituted. We measured the changes of length and lateral shift of the channel using GIS methods. Three development periods were identified based on our results. In the first period the development of the river was characterized by natural processes. Then, the development of the river altered owing to the antropogenic impacts. In this transient phase the average shifting of the channel was 7.43 m/y. In the third term this value reduces to 0.2 m/y as the river is getting to reach the equilibrium stage.