Flood in Assam: Causes & remedies

Gunin Borah

(The writer can be reached at borah.gunin@gmail.com)

Floods wreak havoc in Assam every year during the monsoon. Flood causes severe loss of life and property, leaves the economy of the state in shambles. Assam is the land of two mighty river systems – centering the Brahmaputra and the Barak. Each year these two rivers and their tributaries cause floods in vast areas of Assam. The geographical setting of the region, high intensity of rainfall of the South West Monsoon, easily erodible geographical formation aggravates floods in Assam.

This year also more than 30 districts in the State have been severely affected by floods. Generally two districts that do not see flooding are Karbi Anglong West and Dima Hasao.

Assam with its vast network of rivers is more prone to natural disasters like flood and erosion which have a negative impact on overall development of the state. The Brahmaputra and the Barak with more than 50 tributaries feeding them cause flood during the monsoon every 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 are concerned, and it is probably most acute and unique in the country. The flood-prone areas of the state as assessed by the Rastriya Barh Ayog (RBA) is 31.05 lakh hectares against the total area of the state 78.523 lakh hectares, ie about 39.58 per cent of the total land area of Assam. This is about 9.40 per cent of the total flood-prone area of the country.

The flood-prone areas of India as a whole is about 10.2 per cent of the total area of the country, whereas flood-prone area of Assam is four times the national mark of the flood-prone area of the country.

During the 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 floods ravage the flood-prone areas of Assam. The average annual loss due to flood in Assam is to the tune of Rs. 200 crore and particularly in 1998 the loss suffered was about Rs. 500 crore. It was Rs. 771 crore in 2004.

The flood problem of the state is further aggravated due to flash floods by the rivers flowing down from neighbouring states like Arunachal Pradesh, Nagaland and Meghalaya. Flash floods create large-scale devastation in vast areas of the plains, including loss of flora, fauna and human lives.

Another major natural disaster being faced by Assam is bank erosion by the Brahmaputra and the Barak and their tributaries. Huge damage caused due to erosion runs into several hundred crores every year. Bank erosion by the rivers has been a serious issue for the last six decades as more than 4.27 lakh hectares of land was already gobbled up by the Brahmaputra and its tributaries since 1950, which is 7.40 per cent of the area of the state. As assessed, the annual average loss of land is nearly 8,000 hectares. The width of the Brahmaputra has been increased up to 15 kilometres at some places due to bank erosion. New areas are being affected by the bank erosion every year. The riverine fertile agricultural lands of the state are getting reduced due to erosion. It has a negative impact on the rural economy of the state.

One of the key reasons for annual deluge in the state is the high percentage of flood-prone region. According to Rastriya Barh Ayog (RBA), 30.05 lakh hectares of total 78.523 lakh hectares area of the state is prone to frequent floods. The reasons behind this high flood-prone area percentage are both natural and man-made or human induced ones.

Several factors, including natural and artificial, are responsible for the reoccurrence of floods in Assam. The most important cause is that, Assam lies in the heart of monsoon belt and so gets excessive and continuous rainfall every rainy season. Due to this, the Brahmaputra and the Barak, along with their tributaries such as Subansiri, Manah, Kopili, Jia Bharali, Dikrong, Jiadhal etc., get flooded and submerge their catchment areas in the vast plains.

Secondly, the existence of long range of Eastern Himalaya mountain on its northern and north-eastern boundaries, Meghalaya plateau in the south, compels the water to flow down into the vast plain inundating it.

Assam and other north-eastern hilly states are prone to heavy natural and artificial landslides. Landslides and earthquakes send in a lot of debris to the rivers causing the river beds to rise-up and become shallow. The shallow river beds lead to greater floods in the basins.

There are also a lot of human induced factors like destruction of wetlands, oxbow lakes, deforestation, illegal cutting of hill slopes, earth filling the natural ponds, canals, encroachment on river banks etc. Nowadays, most of the cities and towns suffer flash floods, due to poor urban planning. Lack of drainage facilities, drainage congestion due to manmade embankment is one of the crucial factors responsible for urban floods. Urban floods are gradually coming up and visible every year in the rainy season in cities like Guwahati, Dibrugarh, Chennai, Mumbai etc.

Among the manmade reasons, the key cause of floods in Assam is releasing of water from dams situated upstream in Bhutan, Arunachal Pradesh, Nagaland and Meghalaya. The unregulated release of water floods the plains of Assam, leaving thousands of people homeless every year.

The man cannot stop rains from falling or stop flowing surface water from bursting its banks. These are natural events, but we can do something to prevent them from having great impact.

Some methods of flood control have been practiced since ancient times. These methods include planting vegetation to retain extra water, terracing hillsides to slow flow of water downhill, and construction of floodways or manmade channels to divert flood water. Other technique includes the construction of levees, dikes, dams, reservoirs or retention ponds to hold the extra water during the time of floods.

After the unprecedented flood in the country in 1954, the Government of India announced a National Policy on Flood Control comprising three phases- the immediate, short term, and the long term measures of flood. The flood control activities in Assam started after the announcement of the National Water Policy. The flood control policy in Assam, along with various comprehensive plans, was prepared and priority areas were identified.

Till now, the Water Resource Department has taken up works, primarily for the general development of the rural sector, and for the protection of major townships in both the Brahmaputra and the Barak valleys. The schemes have also been taken up to relieve the drainage congestion in cities and other important areas.

The government has taken several flood-control measures to lessen the menace of effects of flood in the State. The immediate assistance of the NDRF and the SDRF flood relief measures, including setting up relief camps, free distribution of foods, cloths, medicines, cash compensation for the loss of property etc., are undertaken by the government. The chief flood control measure has been the construction of embankments along the bank of rivers in the affected areas.

Several measures should be adopted for long-term solution of the flood problem in Assam. One of the main methods used in the state to control flood is embankments, but almost every year the Brahmaputra and the Barak breach their banks, inundating agricultural lands and houses. Checking the embankments before monsoon should be done as we never know where it will be breached.

The permanent destruction of wetlands in the state has also been contributing to the deluge. Assam is the home to more than 3,000 wetlands and many varieties of flora and fauna. The wetlands locally known as beels, oxbow lakes act as reservoirs and rejuvenating them before monsoon can help in mitigation of flood in parts of the state. Wetlands play a very significant role as natural reservoirs of water that absorb part of flood water from the nearby rivers through their catchment channels and also from surface runoff.

Noted environmentalist of the Northeast, Dr. D.C. Goswami said, "To mitigate floods, any potential practical solution should be based on an integrated, multidisciplinary basin management plan focused on water and soil preservation together with geo-environmental, eco-biological, and socio-cultural integrity of the river basin".

The Government of India has prepared a master plan for mitigation of both flood and drought, the interlinking of rivers of India whereby the extra water of the Brahmaputra and its tributaries can be diverted to dry land areas of Western and Southern India, at the minimum cost of marine environment and ecological degradation.

For each river basin, a flood management plan should be developed. In setting up such a plan, consideration should be given to aspects of solidarity within the river basin that is to prevent as much as practicable the passing on problems from one geographical area to another.

The plan should be based on an integrated approach including all relevant aspects of water management, physical planning, land-use, agriculture, transportation, and urban development, nature conservation, at all levels (national, regional and local). In the development of a flood management plan, decision makers at all levels as well as stakeholders and civil society should be involved.