Stormwater Management and Road Tunnel or SMART tunnel is 9.7 km length of waterway for flood water diversion, with 3.0 km of the length are dual-function, being applied as both motorway and waterway.
The tunnel construction began in January 2003 and was completed in 54 months. The components forming the complete system of the SMART tunnel are capable of holding in total 3 million cubic meters of water. It can be divided into 2 main categories which are the main structures and flood detection.
Main structures are diversion structure, Berembang holding pond, tunnel and the receiving pond known as the attenuation pond in Taman Desa. The whole system is then connected to the outfall structures, where the water is discharged back into the natural flow, Sungai Klang via Sungai Kerayong in Taman Desa.
The flood detection system includes rainfall, real-time flow, river level and pond water level monitoring. Real-time data is utilised as an input for the hydrological and hydraulic model. The process involves data collection, transmission, processing and analysis to forecast the flood based on the storm characteristics to determine which mode to be activated.
During normal flow conditions in Sungai Klang, SMART is not activated for flood diversion, that is Mode 1. At this time, the tunnel is dry and the motorway is open for traffic. When the flow is over 70 m3/s, the diversion process is activated, utilising only the lower drain section, this is Mode 2. However, when the flow is more than 150 m3/s, Mode 3 will be activated. During this mode, motorway compartments will be cleared of traffic and so the tunnel will be ready for the activation of the final mode, which is Mode 4. Mode 4 will be activated if the heavy rain prolongs. At this stage, the tunnel is running at its full capacity and the motorway will be fully utilised to flow the flood water.
SMART began operating in July 2007. Since then, it has prevented flash floods in the heart of Kuala Lumpur city during almost 600 events of rainfall, including 9 major storms.
MODE 1
Traffic is allowed in the tunnel
MODE 2
Flood water flows down the tunnel (lower drain)
A traffic tunnel was opened for the passage of traffic in and out of Kuala Lumpur.
MODE 3
Flood water flows down the tunnel (lower drain)
The traffic tunnel was closed and emptied of vehicles.
MODE 4
Flood water flows down the tunnel (lower drain)
Traffic tunnel closed and completely emptied of vehicles