A Storm Water Tunnel With Built-in Motorway

Malaysia’s capital of Kuala Lumpur is regularly subjected to flash floods after heavy rains that remain for three to six hours, flooding the city center. After a series of devastating flash floods washed the heart of Kuala Lumpur city center and accumulated losses rose to billions of ringgit, the government approved a never-before-attempted concept to tackle the crippling floods and snarling traffic jams that plaque the Southern Gateway of the city – a SMART tunnel.

SMART stands for Stormwater Management and Road Tunnel. The 13.2m diameter tunnel consists of a 9.7km storm water bypass tunnel, with a 4km dual-deck motorway within the storm water tunnel. The main purpose of SMART is to solve the problem of flash flooding in Kuala Lumpur from the Sungai Klang and Kerayong rivers and also to reduce traffic jams during the daily rush hour.

The dual-purpose SMART tunnel begins at Kampung Berembang lake and ends at Taman Desa lake, diverting floodwaters away from the confluence of the two major rivers that run through the center of Kuala Lumpur. The 4km motorway tunnel incorporated into SMART acts as an efficient alternative route from the Southern Gateway of KL-Seremban Highway, Federal Highway, Besraya and East-West Link from entering and exiting the city centre. For motorists, the tunnel greatly reduces the travel time between the Jalan Istana Interchange and Kampung Pandan – from around 15 minutes down to just four minutes.

The SMART tunnel consist of three sections. The upper two sections are roadways that cater to traffic. Each section allows traffic to travel in one direction only. The third section at the bottom is a storm water tunnel. Under normal condition, when there is low rainfall and no storm, the motorway section is open to motorists and the storm water tunnel is closed. During moderate storm, the SMART system is activated and floodwater is diverted into the bypass tunnel in the lower channel of the motorway tunnel. The upper channel is still open to motorists. During an impending flood, the upper two roadways are closed to traffic and evacuated. Then the entire three sections of the SMART tunnel is ready to carry flood waters.

SMART opened to traffic on 14 May 2007, after four years of construction. The cost of the project was around MYR1,887m (approximately $514m). The tunnel handles 30,000 cars per day and has been used 44 times to divert floodwater. [Kaushik /KPN]