Understanding planform dynamics of the Ganga River in eastern part of India
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Understanding planform dynamics of the Ganga River in eastern part of India Kumar Ashwini1 • Shehnaj Ahmed Pathan1 • Ajai Singh2
Received: 3 July 2020 / Revised: 8 November 2020 / Accepted: 11 November 2020 Ó Korean Spatial Information Society 2020
Abstract To understand the natural processes of planform change, meandering and formation of braid bars, satellite sensor data of few decades play a significant role. The present research focuses on the planform dynamics of Ganga River from Sahibganj (Jharkhand) to Jalangi in West Bengal, India. This study is based on the sequential river planform maps. These maps were prepared using Landsat 1, Landsat 3, Landsat 4, Landsat 5 and Landsat 7 data for the period 1975–2015 at an interval of 5 years. The sinuosity index, braiding index and spatial analysis of maps were used to assess and classify the river into straight, braided and meander categories. This was observed that braiding index is continuously increasing and the meandering index has decreased from 1.6 to 1.24 during 1975 to 2015. The results showed the changes in channel migration with time and space. From the analysis, it is observed that the factors causing shifting of the Ganga River in some areas are natural and anthropogenic. Landsat images were found to be effective in determining the meandering index, braiding index and planform change of a river. Keywords Meandering index Sinuosity index Braiding index Farakka barrage Sahibganj Ganga River
& Ajai Singh [email protected] 1
Department of Civil Engineering, National Institute of Technology, Silchar, India
2
Department of Water Engineering and Management, Central University of Jharkhand, Ranchi, Jharkhand, India
1 Introduction A River is a dynamic and crucial part of the physical environment. Study of the behaviour of a river gives prime importance to wide variety concerns, like flood control, navigation and water resource development to recreation. Meandering is very common to most of the rivers in the world nowadays, which is occurring due to various natural and human activities [1]. Excess of turbulence, slope of the river, streamflow, bed and side resistance capacity are the natural causes of most of the meandering rivers. Human activities also influence the river meandering by constructing a dam, settlement and adopting faulty agricultural practices [2]. Meandering property of a river has attracted many engineers and researchers over the last few decades. In alluvial planes, a meander of rivers consists of a number of consecutive curves connected with short straight stretches crossing. In a plan view, the appearance of a reach describes the pattern of a river. Based on a plan view of a major river, the pattern of a river reach is broadly categorized into three patterns such as straight, braided and meandering [3]. A straight river follows almost a straightline course. A meandering channel follows a sinuous course of Y-shaped or U-shaped, consists of alternating bends. Generally, braided rivers are formed due to poorly defined unstable
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