Abstract
Bangladesh is prone to severe flooding as being located at the confluence of three mighty rivers named the Ganges, Brahmaputra, and Meghna. As a consequence, river flooding and erosion are common natural disasters that severely affect the landscape, lives and economy of the country. Dharla River, one of the trans-boundary rivers originated in the Himalayas, along with Brahmaputra River has a great influence on the recurring floods and erosion in north-western Bangladesh. Almost in every year, excessive erosion and embankment damages caused by Dharla render a thousand of people homeless with massive loss of crops and poultries. As per the environmentalists, this is a matter of huge concern as development of accurate flood maps and erosion prediction for Dharla River has been very challenging. In this study, the flood map and Dharla River bank shifting study have been developed by using HEC-RAS 4.1.0 hydrodynamic model and Landsat satellite images. In addition, the HEC-GeoRAS was used to establish the river reach for HEC-RAS. The calibration and validation have been performed using the observed and simulated water levels for the years of 2013 and 2014 respectively. The HEC-RAS flood water level output was used in HEC-GeoRAS for raster interpolation followed by overlain onto the land surface elevation of the study area. Then, the difference between water level interpolation and land elevation surfaces has been considered as a depth of inundation which is performed in Arc-Map 10.2. Flood maps have been generated for the years 2010, 2013, and 2014 for highest water level of each year. The erosion prone areas have been indicated by analyzing bank shifting of Dharla River for the years 1987, 1997, 2007, and 2017 by digitizing the satellite images in Arc-GIS 10.2. From the observation it has been found that the course of the Dharla River has been shifted vastly since 1987 to 2017 due to erosion.
Highlights
Flood is one of the most devastating disasters in the present world which causes damage to environmental, social, economical, and human lives at about 43% of all natural disasters [1]
Compared to the wide range of research conducted in other flood prone countries, research work carried out in Bangladesh on determination of current status of flood inundation map is very limited [13]
This study provides an easy, simple, and short technique to obtain flood maps for Dharla River by developing a hydrodynamic model of the river using Arc-GIS 10.2
Summary
Flood is one of the most devastating disasters in the present world which causes damage to environmental, social, economical, and human lives at about 43% of all natural disasters [1]. Flood damage potential in Bangladesh is on the rise due to possible causes including climate change, urban concentration in the three river basins and encroaching of settlements in the flood prone areas [5]. According to Annual Flood Report (2012) of Bangladesh Water Development Board, the water Level of Dharla River at Kurigram registered two distinct peaks during the monsoon 2012, in June and July. According to Annual Flood Report (2014) of Bangladesh Water Development Board, the water level at Kurigram attained peak of 26.95 m PWD on 28 August which was 45 cm above the DL (26.50 m) [11]. In 2015, an area of about 100 feet of the Water and Power Development Authority (WAPDA) dam in Bangram area of Khulaghat union was under severe threat of erosion by the Dharla River. The bank shifting has been analyzed by digitizing the satellite images of Dharla River for the years 1987, 1997, 2007 and 2017 using Arc-GIS 10.2
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