The first and most obvious reason is that we are a small island surrounded by the sea. The second reason is that 30% of our land is less than 5m above mean sea level. This is equivalent to 30,000 football fields. And the third reason is that unlike other countries, we do not have abundant high grounds to retreat to.

According to DPM Lawrence Wong, the Government does not yet have good estimates of the cost of the major infrastructural investments needed.
A high-level estimate is that these will cost more than $100 billion over 100 years.
The Government plans to employ a combination of funding methods to finance various climate adaptation measures, in a way that is fiscally sustainable and equitable across generations, DPM Wong said.
Past Reserves
Though the size of our reserves may be big to some, the growth of our reserves is, in fact, not keeping pace with the growth of our economy. For this reason, it would be a mistake to delude ourselves into thinking that we have more than enough firepower to defend the size of our economy in a crisis.
Coastal and Flood Protection Fund and surpluses
In 2020, the Government set up the Coastal and Flood Protection Fund (CFPF) with an initial injection of $5 billion.
With fiscal conditions are good, the Government will be able to set aside monies in this fund for future spending. Surpluses accumulated by the Government are not squandered away in populism. They are carefully stewarded to ensure that the money spent benefits Singaporeans.