Assam with its vast network of rivers is prone to natural disasters like flood and erosion which has a negative impact on the overall development of the state. The Brahmaputra and Barak River with more than 50 numbers of tributaries feeding them, causes the flood devastation in the monsoon period each year. The flood and erosion problem of Assam is singularly different from other states so far as extent and duration of flooding and magnitude of erosion is concerned and is probably the most acute and unique in the country.
The flood-prone area of the
state as assessed by the Rashtriya Barh Ayog (RBA) is 31.05 Lakh Hectares
against the total area of state 78.523 Lakh Hectares i.e. about. 39.58 % of the
total land area of Assam. This is about 9.40% of total flood prone area of the
country. Records show that average annual area affected by flood is 9.31 Lakh
Hectares. The flood prone area of the country as a whole stands at about 10.2 %
of the total area of the country, but flood prone area of Assam is 39.58 % of
the area of the state. It signifies that the flood prone area of Assam is four
times the national mark of the flood prone area of the country.
During
post-independence period, Assam faced major floods in 1954, 1962, 1972, 1977,
1984, 1988, 1998, 2002, 2004 and 2012. Almost every year three to four waves of
flood ravage the flood prone areas of Assam. Average annual loss due to flood
in Assam is to the tune of Rs. 200.00 Crores and particularly in 1998, the loss
suffered was about Rs. 500.00 Crores and during the year 2004 it was about Rs.
771.00 Crores.
Causes of Flood in Assam
- Heavy Rain Fall and Snowmelt Water in Summer: throughout the Northeast India, average rainfall is very high, varying between 100cm to 1300cm. beside about 80% of the annual rainfall comes mainly in the five summer months from May to September. This is also the period when the snow over the Himalayas melt and water therefrom rolls down the rivers to the Brahmaputra valley. The supply of water thus becomes excessive in the rivers and flooding occurs.
- Location Of the Plains: each of the Brahmaputra and Barak plains surrounded on three sides by high hills and mountains. Whenever there is rainfall in the hills and mountains water rushes down to limited plains from extensive catchment areas, flooding the plains.
- Low
Gradient of the Plains: the Brahmaputra and Barak valleys grade very gently towards
their downstream. It is found that the gradient of the Brahmaputra between
Sadiya and Dhuburi is
- Chocking pf the River Channels: the hills and mountains of Himalayas, eastern Arunachal, Nagaland, and North Cachar hills, Manipur, Mizoram and Tripura are made of relatively soft tertiary rockes. The heavy monsoons rain that fall on them further softens the materials casing solifiluction and sheet erosion down the steep slops. The streams carry these sediment to down slop thus their carrying capacity is reduce and the sediment deposited on their beds and chocking the channels.
- Sifting of the River Courses: the rivers of Assam, especially the ones that comes down from the Himalayan and the Tertiary hills change their courses frequently. This is mainly because the rivers carrying enormous quantities of sediments from the hills and on reaching the plain the sediments are deposited on their own beds. The channels thus filled up and the water in the following summers dig out different courses abandoning the earlier once. Besides, the seismic instability of the region also contributes to such shifts.
Important Measures
1.
Constriction
of embankment in a planned manner in some selected areas only.
2.
Controlling
he major rivers by constricting dams and reservoirs.
3.
Cheeking
bank erosion.
4.
Stopping
deforestation and take up afforestation in the catchment areas.
5.
Undertaking
protection work of settlements, both rural and urban.
6.
Constriction
of drainage channels, culverts and sluice gates whenever necessary.
7. Constriction
of raised platforms near the settlement of the flood pore area for taking
shelter for both man and animals.