Chennai city and its surroundings are very flat with contours ranging from 2m to 10m above Mean Sea Level with a few isolated hillocks in the southwest.

Chennai’s monsoons are characterized by clearly marked seasons with specific types of weather. The Northeast monsoon (October-December) is the main season when over 50 per cent of the annual rainfall happens.

Chennai’s terrain necessitates an effective storm water drainage (SWD) system and the Corporation of Chennai has a network covering a length of 855 km. Through this network, rainwater runoff gets drained into the 16 open canals maintained by the Corporation and reaches the sea via four waterways - Otteri Nullah, Buckingham Canal, Adyar and Cooum rivers – under the control of the State Public Works Department.

METROWATER discharges most of its sewage into these canals and waterways! Desilting of the drains is carried out twice a year and canals are desilted once in two years. Structural repairs are also carried out whenever necessary and more drains are constructed on a continuous basis. The corporation is in the midst of implementing a massive Rs 1,400 crore SWD project for which substantial funding will come from the Jawaharlal Nehru National Urban Renewal Mission (JNNURM).

Urban development in Chennai Metropolitan Area has drastically altered its land use pattern. Lands with vegetation have been converted into residential, commercial, industrial and other uses. Buildings, roads, streets and other paved surfaces that have sprung up thereof have reduced permeability of lands thereby increasing the runoff generated from the ‘developed’ lands.

Hence urban drainage systems are designed to carry storm waters that dispose of into major waterways as quickly as possible. Since the second half of the last century, the city has grown densely, not adhering to spatial planning principles, especially in the downstream reaches of the rivers in the city area, affecting the runoff pattern.

Most natural drains have been occupied and constructed upon. According to experts, further urbanisation, as envisaged in the Second Master Plan (SMP) along the south and southwest growth corridors would drastically increase flood peaks in the Adyar and Cooum rivers due to increase in impermeability of the surface and quick flow of storm waters.

SMP has laid down certain policies and strategies to combat floods in the CMA. The most important of them is to utilise flood waters to augment urban water supply through creation of additional storage capacity. Developing a cluster of open spaces to provide green environment would enable flood moderators during heavy monsoon.

Micro-drainage being the responsibility of the local bodies, it needs to be fully and effectively integrated with the macro-system. PWD is suggested as the nodal agency for holistic planning and maintenance of existing water bodies by preventing encroachments and implementation of macrodrainage systems.

The root cause for the floods is choking and blocking of natural drains and ‘infrastructure development’. Typical examples are the monstrosity called MRTS (Mass Rapid Transit System) that has killed Buckingham canal as a flood carrier and indiscriminate road laying and raising of road levels all over the city. The much-touted highspeed elevated corridors on the riverbanks and the ‘expressway’ over Chennai’s beaches could drive the last nail in the coffin! Low quality of material used and poor standard of constructing drains result in their breaking soon thereafter.

Loose sand-fillings under low-quality pavement slabs get into the drains and choke them. The weak maintenance system only adds to the woes.

Management and maintenance of water supply, waterways and drainage system is a merry-go-round between METROWATER, PWD, Chennai Corporation and Municipalities with no single, effective authority in charge.

The result is chaos and confusion, a heady concoction for corruption and non-performance. Institutional reform is an immediate imperative if the city and its citizens are to be spared of this recurring agony.