KMC’s land area is relatively flat and low-lying and its non-uniform slope generally trends away from the river towards the east and south-east. The area lies within the tidal reaches of the River Hooghly, was once a wetland, but now is the urbanised heart of KMA, a highly and densely populated area.
The city initially grew in a roughly north-south direction along a stretch of the River Bhagirathi, but later extended eastwards to encroach upon the back swamps and wetlands. Growth has been accentuated by high in-migration, with many of the incoming population having to live in low-income neighbourhoods across the city located on marginal land located on the floodplain and along the natural drain paths and drainage channels, narrowing them and effectively reducing their capacity. Inadequate drainage of storm water run-off increases the frequency and severity of localised flooding.
The climate of Kolkata is considered to be tropical wet and dry, with an annual mean temperature of 28.3ºC. Much of the rainfall is received from the south west monsoons during the months of June to September. In the last two decades the precipitation has been sporadic, with long dry spells, followed by heavy downpours towards the end of the monsoon season. This usually leads to flooding/ water logging in various parts of the city.
Several studies indicate that coastal urban areas, particularly mega cities located in low lying deltaic regions, are more prone to the risk of coastal flooding. Kolkata is currently ranked as the third most vulnerable city in the world from coastal flooding. The main impacts of these flood events, apart from damage to life and property is the deterioration in environmental health; a decrease in the wellbeing and living conditions for residents; and the impacts that flooding has on the livelihoods.