STUDY OF MEANDERING BEHAVIOUR FOR PARTS OF THE GANGES AND EUPHRATES RIVERS USING GIS

Abstract

River meanders are natural features referring to the bends in the river courses. Meandering rivers erode the sediment from the outer curve of each meander and deposit it in the inner curve downstream. Meandering nature of the rivers, oxbow lake and sediment load cause shifts in the river course. Shifting in the river course may lead to floods causing significant losses. River Ganga is a trans-boundary river of India and Bangladesh, originating from the southern slopes of the Himalayan and flows for 2525 km to the south till the Bay of Bengal. The Ganges basin is one of the largest and the most heavily populated river basins in the world with 0.5 billion people inhabitant. The river enters in the plain of Uttarakhand at Haridwar and flows for about 50 km in the plains up to Balawali. This stretch is the main study area of the present work which is subjected to meandering and shifting leading to floods. Another study area is the 50 km reach of the Euphrates river located in in Alanbar state, Iraq. The Euphrates river originates from turkey and flow through Syria and Iraq. The main objectives of this study are to analyze the meandering behavior and river shifting, delineate the meander belt of the river, and to identify flood vulnerable areas using GIS software and satellite images data. Other objective of the study is to compare the meandering behavior of parts of Ganga river with Euphrates river. Meandering behavior of Ganga river was analyzed from 1972 to 2005. During this period river showed different channel patterns varied between straight single channel river at the beginning of the study period and braided multi-channel river from 1990 to the end of the study period. West bank of the Ganges stretch is subjected to erosion as a result the river is shifting westward; this puts all flood protection structures on the west bank under high flood risk. Some segments shifted with higher migration rates increasing the flood risk in these segments. Meander belt width ranged between less than one kilometer to about 3.5 km. The meander belt width is generally more than 2 km at most of measured sections which is normal for rivers like the Ganga river. Three factors were taken into consideration for flood hazard mapping viz proximity to the river, highest elevation and slope. The result shows that most of very high hazard zones are located around the river stretch because these areas are located on low and flat lands close to the river. V Other separate objective was comparing the meander behavior of the Ganga river with Euphrates river. The comparison of the meandering behavior shows that the meandering behavior of Euphrates is the opposite of Ganga river. The Ganga river is highly an active river which changes its channel pattern whereas Euphrates river is a sinuous single channel river never changed its channel pattern during the study period. Though the study is based on the image data available in public domain and the available toposheets, a few set of the remote sensing data during the flood event could have given better insight in analyzing the meandering and shifting behavior of the Ganges river. Yet, the results will helpful to the local administration for planning the flood protection works in the plains of Uttarakhand. vi