RISK PRONE AREAS FOR FLOOD

 

India can be broadly divided into the following four regions for a study of flood hazard. In addition the Andaman and Nicobar Islands and Lakshadweep have peculiar characteristics, which result in drainage congestion, flooding and erosion in coastal areas.

 

• The Brahmaputra River Region: This region consists of the rivers Brahmaputra and Barak and their tributaries, and covers the states of Assam, Arunachal Pradesh, Meghalaya, Mizoram, Manipur, Tripura, Nagaland, Sikkim and the northern parts of West Bengal. The catchments of these rivers receive very heavy rainfall ranging from 1100 mms. to 6350 mms which occurs mostly during the months of May-June to September. As a result, floods in this region are severe and quite frequent. 

 

• The Ganga River Region: The river Ganga has many tributaries, the important ones being Yamuna, Sone, Ghaghra, Raphti, Gandak, Burhi Gandak, Bagmati, Kamla Balan, Adhwara group of rivers, Kosi and the Mahananda. It covers the states of Uttarakhand, Uttar Pradesh, Jharkand, Bihar, south and central parts of West Bengal, Punjab, parts of Haryana, Himachal Pradesh, Rajasthan, Madhya Pradesh and Delhi. The normal annual rainfall in this region varies from about 600 mms to 1900 mms of which more than 80 per cent occurs during the SW monsoon. The rainfall increases from west to east and from south to north. The flood problem is mostly confined to the areas on the northern bank of the river Ganga. 

 

• The North-west River Region: The main rivers in this region are the Indus, Sutlej, Beas, Ravi, Chenab and Jhelum. These rivers are the tributaries of the Indus. They carry quite substantial discharges during the monsoon and also large volumes of sediment. This region covers the states of Jammu and Kashmir, Punjab and parts of Himachal Pradesh, Haryana and Rajasthan. Compared to the Ganga and the Brahmaputra river regions, the flood problem is relatively less in this region. The major problem is that of inadequate surface drainage which causes inundation and water-logging over vast areas.

 

• The Central India and Deccan Region: Important rivers in this region are the Narmada, Tapi, Mahanadi, Godavari, Krishna and Cauvery. These rivers have mostly well defined and stable courses. They have adequate capacities within the natural banks to carry the flood discharge except in the delta area.