What has been happening in Bangladesh over the years is just opposite to what was warranted. We have been eagerly filling up the surface water bodies, the ponds, dighis, khals, bils, and lakes. The pressure of population growth and urbanization has certainly contributed to this process. But, this process of filling up of the surface water bodies has been very detrimental to flood control effort.
In the older part of the delta, even historic rivers are getting filled up. For many years now, due to Farakka and other upstream diversions, the lean season flow of Bangladesh rivers has decreased. This has been particularly true for rivers in the western part of the country. Many riverbeds now become totally dry during the winter season. This has made it possible and encouraged people to fill up the river beds and use them for other purposes.
Unfortunately, as we noted, Bangladesh is headed toward a situation of extremes, whereby very low lean season flow will be accompanied by very high peak season flow. Only a massive excavation program can enable Bangladesh to cope with this twin problem of extremes simultaneously.
On the one hand, excavation will keep riverbeds wide, open, and deep so that peak season flow can pass through easily and rapidly. It will also enhance surface water storage capacity, which will thereby lower the flood height. On the other hand, the stored water in the re-excavated water bodies will counteract the shortage of water during the lean season. Unlike embankments, an excavation program can significantly enhance the dry season irrigation potential.
Sometimes it is argued that excavation and dredging is too big a task. Dredging of the main rivers is of course an enormous task. But that should not prevent Bangladesh from embarking on an energetic program of excavating the smaller rivers and other surface water bodies. In fact, Bangladesh should immediately start with a program of rejuvenating the distributaries of Padma in southwestern districts of the country.
It is quite likely that filling up of these distributaries has been one reason of increased flooding in recent years of regions south of Goalondo, including Dhaka. The rivers of North Bengal should also undergo this process of re-excavation as soon as possible. There are quite a few aspects of Bangladesh’s situation that should prove favorable for a nation-wide excavation program. Some of these are as follows.
First, Bangladesh’s massive population should be a tremendous help. The density of population in Bangladesh has now reached almost 1000 per square kilometer. If the water bodies targeted for excavation constitute even 10 percent of the area, then we would have 10,000 persons per square kilometer. With this high density of population, clearly, re-excavation should be manageable task.
Second, excavation program does not require imported inputs and hence does not demand foreign currency. It is a labor-intensive operation and hence should be helpful in generating a huge amount of employment in rural areas. Also, not all the labor may have to be fully paid. With appropriate national leadership, some of this labor may be partially or fully voluntary.
Third, it is an important fact that rivers and most large water bodies in Bangladesh are under khas,or government, ownership. This means that in implementing an excavation program, the government will have to face fewer legal problems and fewer expenses. This should be a big advantage. By contrast, construction of embankments usually requires confiscation of land and paying of compensation to its owners. This makes embankment program often legally problematic and financially expensive.
Fourth, the current reduced lean season flow should make the task of re-excavation technically easier. In many cases, there will no need for creating temporary diversion channels. The excavation program can gradually move from smaller river and water bodies to those of larger size. Note that this program may not be limited to re-excavation only. In certain cases new canals may also be constructed. However, to save land, it is always a good idea to re-excavate the existing ones than to construct entirely new ones.
Roads have been often constructed without adequate number and size of culverts and bridges. Travelling in the western districts, it is not unusual to find an entire river filled up from both sides and spanned by a culvert of pathetic size in the middle. A lot of corners have been cut because of either misconception or sheer greed. This has now resulted in many unnecessary obstructions and bottlenecks.
Roads are certainly needed. However, in view of Bangladesh’s situation, the following principles need to be observed. First, it is better to expand and make more intensive use of the existing roads than to build entirely new ones. That is, construct new roads only if these are absolutely essential and there are no other alternatives available.
Second, roads should be aligned with the rivers as much as possible. Third, in all cases, leave maximum passage for water by inserting bridges and culverts of adequate number and size. Fourth, given that large sums have to be spent in repairing roads damaged by flood each year, in some cases it may be cost-effective to have entire road constructed in the form of bridge.
These principles imply that some of the existing roads will need modification. In particular, at points where these roads do not have adequate passage for water, they need to be reconstructed. The excavation program and the programme of alignment and modification of roads will have to be implemented with an eye to restoration and enhancement of waterways. Note that water-transportation no longer has to be a slow mode of transportation. With engines fitted even to the country-boats, the rejuvenated water transportation will be qualitatively different than that featured in the pre-industrial equilibrium.
The excavation programme will have to go hand in hand with a programme of revival of the fisheries. Over the, fresh-water fisheries sector of the country has suffered considerably. In part, this has been the result of filling up and lean season drying up of the water bodies. A second reason has been the increased use of chemical fertilizer and pesticides. The runoff from fields with chemical fertilizer and pesticides often had devastating effect on the fisheries stock of the adjoining water bodies. The opening up strategy will help to restore fisheries in two ways.
First, excavation of inland water bodies and reestablishment of their connections with rivers will enhance the fishing habitat. Second, river inundation will help agriculture to be less dependent on chemical fertilizer, thus reducing the problem of chemical run-off.
