CNN has named KL’s SMART Tunnel among the top 10 world’s greatest tunnels in its recent article, citing the engineering marvel’s ability to switch from a flood relief channel back to a busy road within hours.
Opened in 2007, SMART was designed as a flood mitigation system for a city that is prone to flash flood, on the account that it sits on the confluence of two rivers.
A popular short cut to KL’s Southern gateway – exits and entrances are located in Sg Besi, Jalan Tun Razak near TRX, and one end of Jalan Sultan Ismail - it may not be immediately obvious to commuters that the tunnel is essentially KL’s largest drain.
Its name pretty much spells out its functions: Stormwater Management and Road Tunnel.
“SMART can operate in three ways.
When there's no flooding, it serves purely as a road tunnel.
When there are floods, rainwater can be diverted into a lower channel, and the upper level will remain open to traffic.
When exceptionally heavy floods occur, the tunnel closes to all traffic and watertight gates open to allow floodwater to flow through.”
Among other tunnels listed in the Top 10 were the recently opened 57km Gotthard Base Tunnel that allows train to pass beneath the Alps, the UK-France undersea Channel Tunnel, and the Tokyo Bay Aqualine.
SMART was commissioned after an earlier study found that the critical stretch of Sungai Klang -- between Sg Klang /Sg Ampang confluence and Sg Gombak/ Sg Klang confluence – is prone to flooding. The river is further constrained by the low Jalan Tun Perak Bridge near Masjid Jamek.
During heavy storms, the SMART system diverts quick rising flood water from entering this critical stretch via a holding pond, bypass tunnel and storage reservoir, thus reducing the flood water level at the Jalan Tun Perak Bridge and preventing spillover into the city.
The mid-section of the 11.5 km long, 13.2 km diameter SMART tunnel also doubles up as a two-level road that can cut travel time from Sg Besi to Jalan Tun Razak to seven minutes at normal traffic time.
Extensive monitoring stations ensure there is sufficient time for the last vehicle to exit the tunnel before the automated water-tight gates open.
Photo credit: GAMUDA