MODE 1
When weather is fair with little or no rain and traffoc is allowed in the tunnel
MODE 2
Activated when moderate rainfalls and the flow rate recorded at the confluence of upper Sg. Klang/Sg. Ampang (L4 flow station) is 70-150 m3/s. Only 50 m3/s is allowed to flow downstream
Excess flood water will be diverted to SMART storages and only the lower drains of tunnel will be used to convey flood flow to the Desa attenuation pond
Road tunnel will still be opened to traffic
MODE 3
Activated when major storm event occurs and flood model forecasts a flow rate of 150 m3/s or more at L4
Traffice will be evacuated from the road tunnel. This normally takes about one hour. Only 10 m3/s is allowed to flow downstream
If heavy rain storm stops early or due to some specific circumstances, then the traffic tunnel will not be flooded
Road tunnel will be re-opened to traffic within 2-8 hours after closure
MODE 4
Activated if heavy rain storm prolongs, usually will be confirmed 1-2 hour after Mode 3 is declared
Road tunnel will be used for passage of flood after traffic evacuation completed. Only 10 m3/s is allowed to flow downstream
Road tunnel will be re-opened within 4 days of closure