Antiquated drainage system The present storm-water drainage system in Mumbai was put in place in the early 20th century and is capable of carrying only 25 millimetres of water per hour, which was extremely inadequate on a day when 993 mm of rain fell in the city. The drainage system was also clogged at several places. Only 3 'outfalls' (ways out to the sea) are equipped with floodgates, whereas the remaining 102 open directly into the sea for more than 24 hours. As a result, there is no way to stop the seawater from rushing into the drainage system during
high tide. In 1990, an ambitious plan was drawn to overhaul the city's storm-water drainage system, which had never been reviewed in over 50 years. A
project costing approximately 6 billion
rupees was proposed by UK based consultants hired by the
Brihanmumbai Municipal Corporation to study the matter. Implementation of the project would have ensured that rainwater did not flood the streets of Mumbai. The project was planned to have completed by 2002 and aimed to enhance the drainage system through larger diameter storm water drains and pipes, using pumps wherever necessary and removing encroachments. The project, if implemented would have doubled the storm water carrying capacity to 50 mm per hour. The BMC committee had rejected the proposed project on the grounds that it was "too costly". These were a few of the drawbacks due to which the city suffered so gravely.
Uncontrolled, unplanned development in Northern Suburbs Development in certain parts of Mumbai is haphazard, and buildings are constructed without proper planning. The drainage plans in the northern suburbs are chalked out as and when required in a particular area and not from an overall point of view. The Environment Ministry of the Government of India was informed in the early 1990s that sanctioning the Bandra-Kurla Complex, a commercial complex in northern Mumbai, was leading to disaster. No environment clearance is mandatory for large urban construction projects in northern Mumbai. Officials in the environment ministry claimed that it was not practical to impose new guidelines with retrospective effect "as there are millions of buildings".
Destruction of mangrove ecosystems , Mumbai on the verge of overflowing.
Mangrove ecosystems which exist along the
Mithi River and Mahim Creek, are being destroyed and replaced with construction. Hundreds of acres of swamps in Mahim Creek have been reclaimed and put to use for construction by builders. These ecosystems serve as a buffer between land and sea. It is estimated that Mumbai has lost about 40% of its mangroves between 1995 and 2005, some to builders and some to encroachment (
slums). Sewage and garbage dumps have also destroyed mangroves. The
Bandra-Kurla complex in particular was created by replacing such swamps. Mindspace CBD (
Inorbit Mall) in Goregaon & Malad has been built by destroying a large patch of mangroves in Maharashtra. == Academic research ==