Noted sanitation and drainage expert Dr Binoy Kumar Das is of the opinion that rise in the size of built-up areas is a major cause for the failure of the Guwahati drainage system. Dr Das is one of the architects of the city's 1971 drainage and water supply master plan. Talking to this correspondent, he said that there was no short cut to remove the havoc caused by improper provision of storm drainage in the Guwahati Metropolitan Development (GMD) area. He held those in power too responsible for the problem. They have been misusing the rural development money. They have also effected amendments to the Guwahati Municipal Corporation Act and Assam Municipal Act, granting voting rights to the encroachers of the hills, wetlands and Government land contrary to legal provisions, he asserted. He said, about 30 to 40 years back, pucca areas, through which water cannot percolate down, hardly constituted ten per cent of the GMD area. Then, the other areas allowed water to infiltrate down. Many low-lying areas were also there that could retain water for some time. Now, inside each of the compounds, almost entire of the plot is cement-plastered. This, together with the impermanent roads and drains, make the storm water rush about in search of permeable points or channels to withdraw from the plain areas. It is obvious that this situation has reduced the status of the city roads into storm water drains, he said. To him, the design of the storm water drains needed change. The drains should be made trapezoidal in shape with earthen bottoms and the sidewalls with enough weep holes. Silt traps at regular intervals with upper barricades to trap floating objects should also be provided within these drains. The drains should also be designed as open ones, he said. Moreover, storm water reservoirs must be surveyed and their boundaries demarcated with permanent pillars and kept free from encroachers, he suggested. The long-term measures to solve the problem, he said, should include, besides the above, a specific chapter in the Building Byelaws for environment protection. The provision of this chapter should be made mandatory for all new constructions and renovations keeping 40 per cent of plot area unpaved and covered with grass. Rainwater should be stored below the plinth of the structures as much as possible and the rest amount be recharged underground within the plot concerned. The buildings should have scientifically designed and very effective septic tanks with the provision of further treatment, soakage and percolation of the effluent through soakage pits. Sullage or gray water from bathrooms and kitchens be collected, treated and allowed to be percolated through the above soakage pits or similar arrangements. Moreover, systems for compulsory separation of garbage as organic and other wastes at the household level, provision for properly designed organic waste digesters and storing of other wastes separately at least for seven days inside the plots concerned, for collection by the agencies for further separation and re-use, should also be there in the new buildings, among others, he said. Explaining his observation on the rural development fund, he said that failure of the rural development programmes was responsible for the loss of most of the hills, wetlands and Government land in and around Guwahati and other urban areas of the State. For, village folks are now rushing to the urban areas in increased number in search of livelihood. The short-term measures, he suggested, include alignment and deepening of the Mora Bharalu on its entire stretch. Besides, satellite imagery should be used to pinpoint the low-lying areas for demarcation and development as storm water reservoirs, even by acquiring private land, he said. Survey around each hill or hill range to locate catch water drains and low-lying deep areas for holding the hill run-off, small earthen dams to retain water and silt at higher levels are also required as short-term measures, he said. Further, he said, the possibility of developing a catch water drain along the oil pipeline should be examined to drain out the hill run-off either to the Deepor Beel or to the Bondajan.