There are apparently 2 main factors that would bring down a tree - a wind velocity of at least 30 km/h and a rainfall intensity of at least 20 mm/h. These 2 factors coupled together were like a lethal concoction. Trees were more prone to come down during such events. No, it was not the rainfall amount or duration. The statistics showed that the source of tree failure was the saturation of soils as a result of soaking in a perched layer of water and the trigger was the strong winds.
The list of the top 6 trees that were documented to be prone to fail under such conditions is as follows in order of high to low incidences:
- Hevea brasiliensis (common name: Rubber Tree)
- Albizia falcataria (common name: Matchstick Tree)
- Cinnamomum iners
- Spathodea campanulata (common name: African Tulip Tree)
- Eugenia grandis (synonym: Syzygium grande; common name: Sea Apple)
- Acacia auriculiformis (common name: Earleaf Acacia)
Now that the Northeast monsoon is approaching soon, efforts have been stepped up to inspect and prune the trees, where necessary, to prevent the uprooting of trees and snapped branches. But the message we need to pass on is:
"Trees are living things, there will always be some trees which uproot, or branches which snap in bad weather. NParks is doing all it can to minimize these instances."
It was truly a valuable lesson well-learnt.