The two trees that fell in Sembawang Park on Thursday night - with one leading to 14 people being injured - were last inspected in May last year and found to be healthy, the National Parks Board (NParks) said yesterday.
The uprooted trees appeared to have fallen due to heavy winds, based on the direction of the falls and their large sizes, Mr Chuah Hock Seong, NParks' group director of parks, said in a statement, adding that investigations are ongoing.
The two mature trees were uprooted at about 5.30pm at the park on Thursday during an intense thunderstorm with gusty winds.
One of the trees, which was 21m tall, fell onto a shelter in the park, injuring a group of SMRT workers who were having a Christmas gathering. The group of 17 friends had sought refuge there after it started raining heavily, and 14 of them were taken to Khoo Teck Puat Hospital after the shelter collapsed.
As of Thursday night, most of them had been discharged or treated for light injuries such as cuts and head wounds requiring stitches.
The tree that fell on the shelter was an Erythrophleum suaveolens, commonly known as the ordeal tree, and was about 3.1m in girth.
The other tree was a Tabebuia rosea, also known as the trumpet tree, and measured about 18m in height and 3.6m in girth.
FEWER TREE FALLS
With the strengthening of our tree management regime over the years, the annual number of tree incidents has fallen by about 85 per cent, from 3,000 in 2001 to about 400 as of December 2018, despite more intensive rain and stormy weather.
MR CHUAH HOCK SEONG, the National Parks Board's group director of parks.
We have been conducting our camps here every year for the past five to six years without trouble... But after Thursday's incident, we will move indoors when the weather turns bad as it seems the shelters might be unsafe too, especially for the children.
MR JEREMIAH TAN, who is organising a church youth camp at Sembawang Park for about 100 participants aged three to 19.
The area affected by the tree falls at the park has been cordoned off to facilitate tree clearance works, but the rest of the park is still open to visitors, said Mr Chuah.
NParks is the central agency for the maintenance of public greenery. It manages about two million trees along streets, in parks and on state land.
Detailing the tree management measures it has taken, Mr Chuah said that NParks has had a comprehensive programme in place since the early 2000s, which includes "a rigorous regime of inspections and pruning, the use of specialised equipment and professional certification of staff".
Tree inspections are carried out based on tree care guidelines by the International Society of Arboriculture. Since November 2016, NParks has carried out advanced inspections of trees that are more than 4m in girth, and is currently developing modelling tools to better understand the behaviour of trees in different environmental conditions, said Mr Chuah.
"With the strengthening of our tree management regime over the years, the annual number of tree incidents has fallen by about 85 per cent, from 3,000 in 2001 to about 400 as of December 2018, despite more intensive rain and stormy weather," he added.
He said that in addition to pruning and inspecting of trees, NParks officers carry out checks when they do their routine rounds along streets and in parks.
"These checks are intensified during periods of adverse weather conditions to pick out trees for targeted tree pruning and crown reduction, or more detailed inspection," he said, adding that officers also check affected sites after any storm event to identify storm-damaged trees and take necessary mitigation measures.
He also said the frequency of inspection and pruning ranges between one and two years, and varies with a number of factors, such as location, species, age and the condition of trees, with higher frequency for some trees and places.
He noted that this frequency is more stringent than the recommendations by the International Society of Arboriculture.
When The Straits Times visited the park yesterday morning, workers were seen clearing the fallen tree and debris at the site of the damaged shelter.
Mr Jeremiah Tan, 22, who was organising a youth camp for Ambassador Baptist Church at the park for about 100 participants aged between three and 19, said that the group will move indoors when it rains rather than seek shelter within the park.
The camp started on Tuesday and will end tomorrow. The group is staying at The Boys' Brigade and The Girls' Brigade campsite next to the park.
"We have been conducting our camps here every year for the past five to six years without trouble," said the National University of Singapore undergraduate.
"But after Thursday's incident, we will move indoors when the weather turns bad as it seems the shelters might be unsafe too, especially for the children."