51 Geocarto International, Vol. 18, No. 4, December 2003 E-mail: geocarto@geocarto.com Published by Geocarto International Centre, G.P.O. Box 4122, Hong Kong. Website: http://www.geocarto.com Geomorphological Manifestations of the Flood Hazard: A Remote Sensing Based Approach Vikrant Jain and R. Sinha Engineering Geosciences Group, Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur - 208 016, India E-mail: rsinha@iitk.ac.in Abstract Flood hazard is one of the most severe problems in the Himalayan river basins. Although floods are essentially hydrological phenomenon, the uneven distribution of floods in the river basin highlights the control of geomorphological and geological factors. A proper understanding of these factors is critical for a successful flood management programme. Remote sensing data is of immense value in evaluating the geomorphological and geological controls in flooding. The present paper highlights the control of geomorphology and neotectonics on flood hazard in north Bihar Plains, eastern India. The Indian Remote Sensing (IRS) data has been used and a variety of image processing techniques have been employed. Introduction The Indo-Gangetic Plains are drained by some of the largest river systems in the world. These plains are also severely affected by frequently occurring disastrous floods and are presently regarded as the worst flood affected region in the world (Agarwal and Narain, 1996). Almost every year, monsoon floods in the Indo-Gangetic Plains cause countless misery to the inhabitants living on the floodplains. The plains of north Bihar in eastern India have recorded the highest number of floods in India in the last 30 years (Kale, 1997). In the last 5 decades, the flood management programs on the rivers of Indo-Gangetic Plains have largely failed. The available data suggest that during 1954-1990, more than 2700 billions of rupees were spent on the flood control measures in India, but the annual flood damage increased nearly 40 times and annual flood affected area increased 1.5 times in this period (Agarwal and Narain, 1996). These data emphasize the need for a better understanding of the flood hazard in these plains. The advent of satellite remote sensing data has facilitated a fuller appreciation of geomorphological and geological factors of floods apart from hydrological understanding available from meteorological and hydrological data. This paper demonstrates the use of satellite remote sensing data for assessment of flood hazard in the Baghmati river basin of north Bihar plains in eastern India and, coupled with hydrological data and field observations, provides some understanding of causative factors of flooding. Study Area Description The Baghmati River is a foothills-fed river (Sinha & Friend, 1994) originating in Kathmandu area in Nepal and draining the interfan area between the Gandak and Kosi megafans in north Bihar alluvial plains, eastern India (Fig. 1). The total basin area of the river system is about 8848 km 2 . Flooding in the Baghmati River basin is a regular Figure 1 Location map of the Baghmati River basin alongwith major sub-surface faults (after GSI, 2000) .