Flood Control in Assam
Unless appropriate steps are taken, Assam will move inexorably towards a deep crisis: the recurrent problem of flooding and its myriad of devastating effects. Last summer, the ferocious flood of 2004 hit hard the river basins of Brahmaputra and Barak. It was a rude awakening and a grim reminder of Assam’s unfortunate geotectonic positioning on the surface of the earth. Every summer, a ritual monsoon brings devastating flood waters to the doorsteps of the people; the poor villagers especially suffer immense loss. Political leaders make statements about the gravity of the situation, activists get vocal, but the floods continue to cause damage year after year. When the waters recede and the cheerful dry harvesting season begins, people tend to forget about the flood damage until it happens again the following summer. The startling fact is that after about half a century of flood control measures and billions of rupees spent on them, the fury of flooding remains largely undiminished. Something has gone awry with flood control programs, all the plans and master plans which have been touted over the past years. Clearly, it is time to take a hard look at the whole situation and to move quickly ahead with a new course of action.
A quick top level look at the flood control situation in Assam reveals that flood relief is slow to come. Out of a total land area of 7.8 million hectares in Assam, more than 2.8 million hectares (about 36% of the total area) were affected by flood this year. The fact that the projected flood protection area is less than 200,000 hectares for both Pagladiya dam and Tipaimukh dam and the fact this is not going to happen until the end of the 11th five year plan (2012), the scenario looks dismal to say the least. Additionally, reduction of only about one meter in the flood level in downstream Brahmaputra as a result of cascades of dams on Dihong and Subansiri does not bode well for planned flood protection for Assam.
All the flood control efforts thus far seem to have been without a concerted overall vision and long term comprehensive planning. At best, they are inadequate stop-gap and band-aid type approaches with lack-luster performance history and without focus on needed serious timeline and resource commitment. In the mean time, Assam is reeling in agony. Ninety four people lost their lives by drowning in flood waters as of October 11, 2004 in Goalpara district. According to HK Das (AT, October 10, 2004) 261 people lost their lives during the early stages of the flood. In addition, there is a constant barrage of bad news about landslides, erosion, and flash floods. Majuli is now 50% its original land, and river erosion is devouring Assam’s land area every year at an alarming rate. This is truly a horrible wake-up call for all, especially the government. Looking at the positive side, this is also an opportune moment for the government to embark upon a massive flood control program; this would provide the youth with employment opportunities to keep them from going violently astray.
The most popular flood control measure in Assam undertaken so far is the construction of over 4000 km of earth embankments. The track record of these embankments leaves a lot to be desired in terms of effective and beneficial flood control. They have been largely unsuccessful and much of them have outlived their design life. These embankments have been put together without consideration of short and long term adverse effects, like waterlogging and loss of soil fertility. It’s time to revisit the design and to embark upon a new reconstruction program providing strength, stability, flow control devices, and enhanced elevation.
The second strategy of flood mitigation is dredging the river beds; this is especially significant with respect to the Brahmaputra and its tributaries since situation and other factors have raised their beds over the years and exacerbated flooding around their banks; however, no significant dredging has been attempted thus far. Execution of dredging projects without potential corruption is a prerequisite for dredging to be successful. Additionally, a plan must be designed for the disposal of dredged material. The dredged material can be programmatically used for filling low lying areas, and they can be reclaimed for building housing on higher grounds. This modern housing is likely to encourage people to relocate for their protection against flood. If it is required to ask people to move from ancestral homes to make room for justifiable hydro-power project reservoirs, this may be a good incentive for the people to make that favorable decision. If the Brahmaputra is dredged around Guwahati, the streets of Fancy Bazaar will not be consumed by knee-deep water as a result of spillover, and businesses will not fall into a lull. It is the businesses’ responsibility as well to press upon the authorities to embark upon such a beneficial measure. Right now there does not seem be any significant dredging operation anywhere; a dredging program needs to be launched immediately with adequate funding and a corruption-free administrative mechanism.
Constructing dams on rivers to impound excess water is a proven method for controlling floods. Thirtyfour dams control flooding of the Mississippi River (USA), thereby saving $200 million in damage every year. Other examples abound around the world; however, the wisdom of building big dams to control flooding need to be assessed on a case-by-case basis. There are a multitude of concerns for numerous environmental effects of building big dams. In general, most can be minimized but not completely eliminated. Acceptability depends on a risk-benefit trade.
Any consideration for a dam should be subject to extremely careful technical review from the viewpoint of safety in a credible earthquake shock environment. Years ago, this author researched seismic design of concrete arch dams for his doctoral thesis at the University of Southampton, England and later was heavily involved as a seismic design specialist in the design of many BWR and PWR nuclear power plants in the USA. Seismic design was on the bull’s eye at that time because of its paramount importance with respect to safety. One cornerstone of the review process of the Nuclear Regulatory Commission (NRC) in Bethesda, MD was to scrutinize in detail the seismic design of structures, systems, and components in the plant. There were cases in which active plants designed by renowned firms had to be shut down for seismic inadequacies. As is well known, over the years, safety issues eventually grounded the entire nuclear power plant industry in the USA. This is an example of safety awareness and action. Given the catastrophic nature of the effects of a big dam failure, it is imperative that a stringent review process be instituted by the Assam government before accepting any proposal for building any dams in and around Assam. Such a third party review should involve top seismic experts of the world. One conspicuous aspect of big dams planned in the North East especially in Arunachal Pradesh is that they are power-centric and not so much for flood control. More than 20,000 Mega Watts are envisioned for these two hydro-electric power projects, but as mentioned earlier in this article, even when completed in 1912 at the end of the 11th five year plan, the two cascades of dams, one at Subasnsiri and the other at Dihang in Arunachal Pradesh, will have very little effect on flood control in Assam. Yet the burden of risk Assam is tacitly asked to assume for possible and probable failure of these dams and subsequence deluge in Assam, particularly in eastern part of Assam, is truly horrendous.
For Assam, the risk of building big dams in any state in the northeast region far outweighs benefits because of the fact that the whole region is characterized by high seismicity. It is well known that in the entire recorded history of mankind, Assam has experienced two of the most severe earthquakes, each with a magnitude of more than 8.5 on the Richter scale. Given the highly statistical nature of the derivation of the design ground response spectrum, site characteristics, incompleteness of data and rampant fault lines in the NE region, it is perhaps impossible to arrive at a reliable 3-sigma design let alone a perfectly a safe design with required confidence level. It is, therefore, advisable that the BOARD/NEEPCO/GOI abandon the plans to build big dams altogether and concentrate on extensive and benign alternate methods like dredging and embankments and others available methods. 26 million people should not be “sitting ducks” in the case of a catastrophic dam failure during a major earthquake of the kind experienced in 1950 and subsequent deluge.
It would be interesting to see what the task committee on flood recommends in their report by the end of the year 2004. Whatever the recommendation may be, it will not happen overnight. But the focus of flood control immediately, among others, should be “flood-plain regulation, scientific and extensive flood forecasting and flood warning systems, raising of houses, important communications and tube wells above the flood levels, and storage of adequate food and fodder on raised platforms etc.” (RB Shah-ex Chairman of CWC).
The last but perhaps the most significant aspect of flood control is implementation without corruption. The upper echelon should eschew corrupt practices in implementing flood control projects. With a rampant corruption culture in the Assamese society, this may be asking for too much. Sacrifice of personal enrichment is a pre-requisite to saving Assam and gives it a solid foundation for progress, peace, and prosperity.
Dr Umesh C. Tahbildar, West
Windsor, New Jersey.