My feedback to Housing & Development (HDB) on soil erosion and tree fall at Bukit Batok south hill, aka Bukit Batok hillside park hill 2 (via One Service)

Dear Sir/Madam,

Earlier today, I noticed that parts of Bukit Batok South Hill area (next to Bukit Batok hillside park) have been denuded of trees and shrubs, and the heavy monsoon rain has washed the exposed topsoil away, causing soil erosion.

Heavy monsoon rain causing soil erosion and tree fall at Bukit Batok south hill next to Bukit Batok hillside park area on 13 August 2022 morning

On a steep slope along Bukit Batok West Ave 9 opposite Block 467B, the clearing of vegetation appeared to have resulted in a tree losing its stability and falling onto the pavement.

Tree fall in a steep slope where shrubs and other plants have been removed

This is worrying not only because such tree fall may cause obstruction and potential injury to any passers-by, but also because the hills in Bukit Batok and Bukit Gombak have a long history of slope failures and landslides (in view of their geology, topology, etc, which make them vulnerable to the negative impacts of urban encroachment).

These hazards suggest that we have crossed the ecological threshold through rapid deforestation and urbanisation – please see here for reference on a recent slope failure at Bukit Batok Hillside Park.

Moreover, along Bukit Batok West Ave 5 opposite Bukit Batok Hillside Park area, the cleared land along the perimeter of the marshy grassland may have caused the pavement to be flooded more easily during wet weather.

The removal of vegetation along the perimeter of the marshy grassland reduces soil permeability and increases surface runoff during rain.

Even if the clearance of vegetation has been done to prevent overgrowth onto the pavement, it appears to have been done aggressively to the point where there is less tree and shrub cover to absorb the rainwater.

As this low-lying area was formerly a depression or valley between Bukit Batok South Hill and Bukit Batok Hillside Park before a road (aka Bukit Batok West Ave 5) was built to divide the two hills in 2018, it remains a freshwater marsh on both sides (which support a fairly rich biodiversity) and is also prone to flash floods.

May I urge the relevant authorities and agencies to keep any trimming or pruning of vegetation to a bare minimum in this area please?

This is to ensure that it will not affect the habitats of the wildlife (which include uncommon forest-dependent species such as red-legged crakes and copper-cheeked frogs, as recorded in the Environmental Impact Studies report) and it will also minimise incidences of flash floods, considering the fact that climate change is causing more frequent and more severe storms as reported in the news?

“As for rainfall, the IPCC said that in general, bouts of rain could become more intense and frequent with each additional degree of warming.”

From “IPCC report indicates Singapore could take bigger hits from climate change” (The Straits Times, 9 August 2021)
The excess water pooling on the pavement during and after rain causes the surface to be wet and slippery, posing a hazard for people

Incidentally, I reported a case via One Service recently, in which the slippery pavement along Bukit Batok West Avenue 5 has caused me to almost slip and fall down while travelling along the pavement. The puddles and flash floods in this area during wet weather may pose a hazard to other pedestrians, joggers, cyclists and food delivery riders who use the pavements.

Tree fall along Bukit Batok West Avenue 5, a likely result of edge effects and habitat fragmentation, where trees along forest edges experience increased wind exposure and other microclimatic changes

Last but not least, I learnt that NParks is currently covering several green areas (including Bukit Batok south hill and Bukit Batok hillside park area) and future parks in an environmental impact assessment (EIA) along Bukit Batok nature corridor, in line with its efforts to reduce fragmentation of habitats in Singapore.

“Mr Lee said that based on findings from the exercise, future environmental studies are expected to consider the ecological connectivity of the development site to other adjacent habitats.

Enhancement works in the nature corridor’s two parks will mainly consist of habitat restoration and other works that will help improve ecological connectivity, he added.”

From “Environmental impact assessment covering 122ha in Bukit Batok to start at end of year” (The Straits Times, 15 November 2021)

It would thus be inappropriate (and even unethical) to remove any trees along this critical part of the ecological corridor, which links Tengah nature way to Bukit Batok nature park and Bukit Timah nature reserve, especially while the EIA and ecological profiling exercise are still ongoing, as it would invariably affect the liveability of the environment and the biodiversity that depends on it.

Otherwise, the findings and results of the EIA may be skewed at the expense of the wildlife residents who live and move around here, as well as the human residents in Bukit Batok who have come to enjoy and appreciate the wild nature, the cool ambience, and the mental health and immune boosting benefits provided freely by the forests along Bukit Batok nature corridor, both now and for many generations to come.

Thank you for your attention.

Yours sincerely,
Jimmy Tan San Tek

P.S. My feedback was submitted through One Service bot in Telegram via the blog weblink due to space constraints, as I wasn’t able to submit it via One Service app due to technical issues.

Approximate locations of tree falls along Bukit Batok West Ave 5 and Ave 9 on 13 August 2022. (Source of base maps: One Service app, National Parks Board and Straits Times Graphics)

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