Throughout Asia, Africa and Latin America 'new towns' are rapidly being built on the outskirts of major cities with the goal of relieving population pressures, according to study author Andrew Rumbach from the University of Colorado Denver.
The towns often sit in high flood risk zones but designers have minimised the dangers through land elevation, new building codes and quality construction.
The problem, Rumbach said, are the informal settlements that invariably crop up beside these new cities and supply their labour force.
When cyclones or monsoons occur, they suffer flooding along with diseases like cholera, hepatitis and dysentery.
"Many nations are aggressively creating new towns. In India, the government has set an ambitious plan to build 100 of them with a million people each by 2020," researchers said.
Rumbach focused his research on Salt Lake, a fully mature new town on the outskirts of Kolkata.
"Kolkata's current perspective plan calls for more than a dozen new town projects to be planned and developed on the city's periphery, settlements that may eventually house more than four million residents," said researchers.
With a population of 300,000, Salt Lake is an affluent city, home to many of Kolkata's elite.
It sits in an area of frequent flooding but drainage systems, underground sewers and elevated pumping stations mean it rarely suffers from natural disasters, said Rumbach who lived in Salt Lake during his study.
But two major slums Dattabad and Kestopur - border the city and are home to many of construction workers, domestic help, food vendors and others who work in Salt Lake.
Rumbach interviewed 598 workers. The majority lived in slums and was employed in Salt Lake.
He found that most lived in cramped conditions which help spread diseases like influenza, cholera and tuberculosis, especially worrisome following heavy rain and floods.
Houses were mostly made of concrete and brick with occasional cheap tile roofs. Electricity was sporadic and scarce, researchers said.
More than 80 per cent of households in Dattabad and 100 per cent of households in other settlements relied on toilets outside their homes, shared by dozens and sometimes hundreds of households, they said.