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Wading through waste water

M. Ali Ashraf
FORMAL city planning in this part of the world began with Sir Patrick Geddess producing a Master Plan for Dhaka in 1917. The plan was never implemented. With the establishment of a planning department in erstwhile East Pakistan, now Bangladesh, in the war 1948. planning activities got an institutional beginning.
A British consultant was engaged for producing the Master Plans for Dhaka and Chittagong; Khulna was added later on. The Master Plans for Dhaka and Chittagong were prepared in 1960 and 1961 respectively.
The plans produced were basically zoning maps, with very little or no reference to drainage planning. Drainage planning was taken over by drainage engineering without any conscious endeavour to integrate drainage planning with the traditional land use planning process.
As a result, engineers built drains and rehabilitated khals on the basis of the existing situation in the catch -
merits they served.They did not give much recognition to the fact that the lands that were Hood plains today would be filled and become a jungle of masonry or concrete buildings tomorrow. Very little provisions were made for flood storage.
Architects and planners, on the other hand, went ahead with their zoning proposals for housing and industries. They allowed building in flood plains without providing for the appropriate drainage. Eyecatching layout plans for new residential areas and satellite towns were produced, where drainage w as given very little importance.
While producing a drainage layout for a residential area we simply forget that these drains would be called upon to drain a much bigger hinterland during a rainstorm than the residential area itself. We have designed inadequate and inappropriate sections for our drains.
No matter whether the road is 20 feet or 60 feet wide, the width of the drains remains constant at 2 to 3 feet. We were very generous in
building roads and highways but were equally miserly in building primary, secondary or tertiary drains of appropriate size.
As a consequence, as expected, drainage became a menace for our cities. Cities in Bangladesh are now paying a heavy price for it. Even an hour of torrential rain is sufficient to inundate low-lying areas of our major cities.
Last year, one-third of Chittagong went under water during the rainy season. There were areas where water remained stagnant for days together, causing serious inconvenience and financial loss to the city'dwellers.
Unlike Dhaka, Chittagong, with hills around, could have ensured an efficient drainage system. But, unfortunately, an appropriate storm water drainage system in Chittagong is yet to be implemented.
In a recent survey in Chaktai Commercial Area, a major seat of trade and commerce in Chittagong, only 14.29% of tire people interviewed were found to be living there for ten years and more. 52.38 % people have been living there for four to six years, while 33% people are living lor even less, only 1 to 3 years, indicating that the business community in Chittagong, unlike in the past, are not finding Chaktai a lucrative place for doing business. 45% of the respondents blamed inadequate storm water drainage and water logging as the main causes of thisdecline.
In fact, it is not a problem for the . Chaktai area only; it is the problem of the whole city of Chittagong. Water logging is a major problem, working as a disincentive and discouraging development of Chittagong. Dhaka, too, is in no better shape. This year, even before the advent of die rainy season, we have seen cars plowing through floodwater in Dhaka streets.
Under the circumstances, we must have a change in our thinking; we must consider a major shift in policy. Conscious drainage planning must become an integral part of our city planning and development activities. To begin with, the following could be a part of our checklist:
• For improving local drainage, tertiary' drainage network for all underdeveloped areas and proposed new developments are to be planned in advance, preferably following the road network. In the case of tertiary drains, attached to the neighbourhood lanes, a minimum drain width and depth of 1 ft 6 inches and 2 ft.
respectively, have to be ensured. Depth will be variable depehd-ingon the topography of the site.
• Following the road hierarchy of the existing city master plans, there should be an approved drainage hierarchy. Provisions for appropriate drainage by the sides of all primary and secondary roads must be made mandatory. II the width of the drainage channel is correlated with the width of the road by a set rule, a lot of confusion can be avoided.
• A minimum width equivalent to l/4(h of the road width is to be kept as drainage reserve on both the side of the road for providing primary and secondary drains. Following the aforementioned proposal, if the road width is 60 ft, then total drainage width by the side of the road will be a minimum of 15 ft. That means, a 7.5 ft wide drain is to be provided on each side of the road. If necessary, covered drains can be used with the dual function of a drain and a footpath. There should be provisions for storm water access to these drains from the adjacent roads. Cleaning doors are to be provided at regular intervals. Implementing the above proposal might become difficult in the existing densely developed areas. But, for all new developments, provisions for drains as proposed above have to be made mandatory.
• Since we are basically aiming at
gravity flow for drainage, and since drainage networks will preferably run parallel to the road network, topography and prevailing natural slopes of the area are to be taken into consideration while deciding directional orientation of the proposed road networks in areas opened for new development. If this is done, drains running parallel to the roads will not face the risk of going against the natural slope.
• Open channels/khals are used as open sewers. We should aim at separating the domestic sewers from the storm sewers. A 20 ft wide service lane can be kept on both the side of the natural khals. At the initial stage, Rajuk/CDA/KDA/RDA can impose a moratorium on development on this stretch of land, 20 ft in width, on both sides of the khals. Currently all domestic sewers are linked with these khals. Interceptor sewer lines can be installed in this reserved land. After installation of the sewer lines this reserved land can also be used as a service lane/pedestrian road and/or a green corridor facing the khals. Khals, once free from domestic sewers, will provide a recreational open space for the city dwellers. Some of these khals may even be used for passenger boat services.
• In the event of installation of underground sewer lines, a sewer treatment plant near the mouth of these primary khals. with the aim of discharging treated effluents to the river, will be required. Site selection and land allocation for the treatment plant will require planning clearance and decision.
Cities should have flood storage ponds at appropriate locations. These ponds can also become a part of the recreational open space in a city. Existing ponds over die size of 0.5 acres are to be preserved, with a ban on filling. The ponds can be marked in a land use map and given an identification number. Constructions on the banks of these ponds are to be discouraged.
Dumping of solid waste in the drains is a behavioural problem
commonly observed in our cities. A massive awareness campaign has to be launched against dumping of waste in the drains. An incentive scheme, tagged with payment of municipal taxes, can be thought of to encourage people to keep their surrounding drains clean and waste free. City Corporations may offer 10% reduction in holding tax to property owners with waste free surroundings.
Conscious drainage planning and its implementation will save our cities from inundation, and the resulting financial loss and inconvenience. The sooner our city planners realise this the better it will be for us-- the city dwellers.
MAh Ashraf is a professional engineer and town planner. He is Chairman of the Institution of Engineers Bangladesh, Chittagong Centre.