|Thanks to Prof Nazrul Islam, Ph.D. for his well written article. Though it raised and was based on a few misunderstanding and misconceptions, it nicely presented many facts with few fallacies related to floods of Bangladesh.
First of all, many of the Bangladeshis do not believe that all the water management projects ("Cordon Approach" as described by Prof. Islam) have failed and bring only sufferings to them. If so, the inhabitants living within the cordoned area (like Dhaka-Narayangonj-Demra (DND), Gonga-Kabodak, Meghna-Dhonagoda, Chandpur Irrigation Project and many more) themselves have destroyed those. Instead, with the benefit of flood free environment, inhabitants are involved in numerous economic activates which lead to their socio-economic uplift. Even during the deluge of 1998 DND, MDIP, Teesta, G-K and many more projects saved millions of population, crops, livestock, public and private properties from the devastation of flood. Then the question, is how the so-called cordon approach failed? With the examples of the implemented projects, demands for new water management projects are coming from the population suffering with the flood and drought.
Populace in the DND panicked in 1974, 1987, 1988, 1998 and this year (2004) and in co-ordination with government organisations, successfully fought with the floods.
Due to the geography and location, flood is an annual expected event in Bangladesh for many reasons. In a normal year about 22 percent country's landmass is flooded. But in a deluge like 1998, upto 68 percent of the country's area remains flooded for several months, which is, of course unexpected. People desperately try to avoid, escape or protect themselves in situation like 1998.
Prof. Islam simplified the flood problem of Bangladesh with the volume of water and area of spread and termed it as a simple physics. If we consider in a close conduit, then the volume-area relationship is absolutely right. But fallacy is that the science of hydrology is not as simple. Area-volume theory is not straightforward and simple for Bangladesh with numerous river networks, huge flood plains, tidal estuary and so on. Volume of water comes from the transboundary rivers and added up with the rainfall turns very dynamic. Huge run-off volume from upper catchments pass through the country to the Bay of Bengal. During the process, comparatively flat and low lying areas are flooded/inundated. This entire process is very dynamic, complex and unique. If a small part of the country is empoldered (or cordoned), due to the dynamic nature of the flowing water, there is no or very little effect on the rest of the area. With the advancement of the computing technology (both in software and hard ware) impact of such empolderement can be evaluated.
Flood in the country is not only linked with the volume-area relationship. Three major catchments of the world the Ganges, the Brahmaputra and the Meghna converge in the country. In a normal year, peak of those three basins do not come together. But when the peaks synchronise, then flood turns into deluge. Increasing communication networks also obstruct the drainage route, aggravate the flood depth. Sedimentation by huge silt (about one third of 2 billion tones annually) in the river bed reduce the total conveyance capacity of the rivers. People are also talking about the impact of long term climate changes and sea level rise on the flooding in Bangladesh.
Another fallacy is that, many opined that retained water in the rivers and flood plains can be used for dry season irrigation. Careful consideration is necessary for this. Estimation and computation is needed about how much water could be retained/stored and what is the irrigation demand for the entire crop season. Water can be retained in the flood plain in post monsoon period (Sep-Nov). Next crop season is Boro, prolonging upto April-May, which is the dry period with minimum rainfall, highest seepage/percolation, hot weather and when evapo-transpiration is the highest of the year. Generally it has been found in many cases that if the stored water is not replenished during the Boro cultivation period, post monsoon stored/retained water is not sufficient for irrigation for the entire period. Cultivation can begin with the residual soil moisture and by using stored/retained water. But the critical demand arises at the flowering stage of the crop (March-April), failure of irrigation at that stage leads to total loss of cultivation. Therefore, water management needs integrated and careful considerations of all the points.
Prof. Islam well mix the technical feasibility of flood management with the social inequalities. Not only in the Cordon Approach, in all the development activities in the world, there is always conflict. Conflict minimisation/management is an essential component of the water management projects of the country. A project leading to a conflicting situation does not mean that it is technically failed.
Floods cannot fully be prevented or controlled, but it can be managed to eliminate/minimize damages. Embankments are not cordoning an area, not fully obstruct entrance of water within the area, never ever considering river as enemies, rather it is managing flood in a better way. All over the world goal of water management activities is to convert the sorrow that originates from river into benefits. In this respect Prof KB Sajjadur Rashid (DU) stated, "it's a sin to live with flood in the technological age of twenty-first century".
Before going for recommendation of Prof. Islam the "open approach", it should be kept in mind that the water management projects of the country enable to produce 7.66 million tons of additional food grain annually, which is about 33 percent of the country's total production. If we go for the open approach, then from where these additional food grain would come from? In addition to that, those projects create million of jobs for the rural poor and provide improved communication network. What would happen to that?