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PUB, NEA on weather patterns, impact of drainage improvement work

Are weather patterns changing?

Are weather patterns changing?

National Environment Agency (NEA): Based on an analysis by the Meteorological Services Singapore of hourly rainfall data between 1980 and last year, there has been a general upward trend in the annual maximum hourly rainfall total — from an average of 96mm in 1980, to 117mm last year.

There has also been an increase of 1.5 days per decade in the number of days each year with hourly rainfall totals exceeding 70mm (70mm corresponds to the highest 1 per cent of hourly rainfall intensity for the period 1980 to 2012). Similarly for temperature, Singapore has experienced an average warming rate of 0.25°C per decade since the 1950s, with more frequent warm days and nights.

The upward trend for rainfall extremes over the past few decades in Singapore is consistent with the global trend towards an increase in the number of heavy precipitation events. Rapid development and urbanisation, as well as global warming, are likely to be significant factors which may explain this trend. It is important to remember that we cannot attribute any single event to climate change. What can be said is that the likelihood of these types of heavy rainfall events is increasing across our region because of climate change.

Has drainage improvement work in certain areas led to rainwater run-off spreading to other areas, as some experts have suggested?

PUB: When planning any drainage improvement work, PUB will conduct detailed site investigations, which include carrying out a topographical survey of the area, checking on the existing drainage systems and reviewing the flood protection measures such as the minimum platform levels and crest levels for developments in the vicinity. The proposed drainage improvement work will be designed such that the drain capacity is enhanced and storm water level in the canal/drain will be lower. Computer simulations are also used to help us analyse the flow of storm water, to ensure that the drainage improvement work, while alleviating floods in affected areas, will not make the adjacent areas worse off than before the work was carried out.

What are specific examples where flash floods have been alleviated because of drainage improvement work?

PUB: Some recent examples of completed drainage improvement work are:

Neram Road outlet drain, which has helped to alleviate flooding along Upper Neram Road

Jurong Port Road outlet drain, which has helped to alleviate flooding along the junction of Jurong Port Road and Jalan Tepong

Roadside drain along Lorong 35 Geylang, which has helped to alleviate flooding along Sims Avenue near Lorong 35/Geylang Road junction

Other areas alleviated by the Marina Barrage include Hong Kong Street, Dakota Crescent, as well as parts of Boat and Clarke Quay.

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