KUALA LUMPUR: The Storm-water Management and Road Tunnel (Smart) justified its RM2 billion waters form the city on Monday.

The tunnel diverted more than 550,000 cubic metres of rain water which would have flooded parts of the city.

The success proved a double celebration for Smart as it was also the tunnel's first flood diversion exercise since its completion in late June.

"Monday's incident proved that Smart was capable of battling flash floods," said Kuala Lumpur flood mitigation project director John Abraham.

Abraham, who was on duty on Monday night, said they started making preparations when the river flow at the Sungai Klang recorded a reading of 70 cubic metres per second.

The tunnel was closed at 9.30pm and reopened at 5am on Tuesday.

It is the world's first dual-purpose stormwater tunnel.