Singapore is looking far ahead to identify the risks of coastal and inland flooding here due to climate change.
National water agency PUB has invited companies to submit proposals to study the extent and impact of such risks for almost half of the island, up to the year 2100.
The area involved comprises 12 catchment areas which make up 46 per cent of Singapore's mainland area, and includes the Bedok, Siglap, Kranji, Joo Chiat and Marina East catchment areas.
A catchment area is a basin, with the boundaries being its highest geographical points. All the water that falls in the basin drains to its lowest point.
A PUB spokesman said the 12 catchment areas were chosen because they are in older parts of Singapore where the ground levels of buildings and developments are generally lower, or they are highly urbanised, or both.
PUB chief sustainability officer Tan Nguan Sen said: "As the waterways in some of these catchments eventually flow to the sea, a sea-level rise or storm surge can have an impact on the flood risks in these areas."
Earlier last year, the international Intergovernmental Panel on Climate Change (IPCC) said in a landmark report that the sea level could rise by almost 1m by 2100 if the most aggressive climate change scenario came to pass.
The global mean sea level between 1986 and 2005 was used as the reference point.
Much of Singapore lies within 15m above sea level, and about a third is less than 5m above the water, the National Climate Change Secretariat said.
To address this, in 2011, the Government raised the minimum reclamation level of new projects by 1m, to 2.25m above the highest recorded tide level.
The PUB study will take into account the IPCC's methodologies and guidelines, its climate projections, and initial findings of the Government's ongoing Second National Climate Change Study.
The contractor is expected to generate flood maps "for extreme rainfall and sea-level rise scenarios due to climate change for the 2030s, 2050s and 2080s, taking into account future land use and stipulated drainage networks".
PUB will also provide details of proposed adaptation measures, such as the widening of drains, tidal gates and pumping systems to be modelled by the contractor.
The agency wants the risks of inundation across the catchments to be specified "in terms of locations, total area affected and flood depth". It added: "This will include providing a list of infrastructure, developments and critical installations that will be affected in a flood area."
The study is expected to start next month and be completed within a year.
Mr Kevin Kho, 53, an engineer with more than 20 years' experience, said the study is timely as the impact of sea-level rises on flooding has been well documented in other parts of the world.
"The problem is a mega one and a real one, and that's why PUB needs to put a lot of thought into it now," he said.