Expert: ‘Hidden’ rivers could cause more landslides in road project

Persiaran Tanjung Bungah 3, which collapsed after a downpour last November. Some of the unoccupied bungalows were damaged as a result. (Pic from Anil Netto’s blog)

GEORGE TOWN: An expert told a forum yesterday how “hidden” underground rivers and waterfalls on the hills of Penang island might mean more disastrous landslides if development is allowed to continue in such areas.

Soil scientist Kam Suan Pheng urged authorities to learn from last year’s rainfall and flood impact in their attempt to build a bypass road which would cross sensitive hill areas.

The road in question is the 10.53km North Coast Paired Road (NCPR), 2km of which will pass through the hill areas of Tanjung Bungah, Batu Ferringhi and Teluk Bahang.

Kam reminded the authorities of the landslide on a hill slope in Tanjung Bungah during last year’s historic rainfall where a road fronting unoccupied new bungalows caved in.

She said the NCPR’s projected route might have a similar topography.

In the Tanjung Bungah incident, she said, the entire road in front of the luxury bungalows caved in, with only a retaining wall holding back the earth from apartments and other buildings below the hill.

She said the authorities had failed to see that the site was sitting on what used to be a river, with a rock face above the bungalows forming a waterfall some 40 years ago.

As time passed, she said, the river was converted into concrete drains as developments cropped up in the area.

Although the river might be expected to flow into the new drains, she added, the forces of nature had pushed it back to its old path.

Hence, the river flowed underground despite being “buried”, she said.

According to Kam, the massive rainfall had triggered the landslide at the bungalow area. She said the old waterfall was “recreated” as rapid waters came down the rock face above the site.

Coupled with the downpour, she said, the spread of the water flowing down the rock face forced it to seep below ground, destabilising the site and causing the road in front of it to cave.

“When rivers cannot take a natural course of flow, they will still try to go through the soil underground. Rivers are never dead.

“My take is, even if we divert (rivers), the drains will be unable to take the rapid runoff and it will definitely go underground.

“As water collects, the soil becomes very saturated and weakens the entire area. The area becomes waterlogged. Saturated soil is heavier than dry soil. That is how the road collapsed.

“This is the likely nature of the route along the NCPR. Isn’t it enough of a lesson for you to think very carefully about whether you want a road like this or not?” she said at a forum titled “NCPR, how is it going to affect you?” by Penang Forum in Tanjung Bungah last night.

The bungalows and road in the Tanjung Bungah incident were located along Persiaran Tanjung Bungah 3, where the units were going for RM1.6 million to RM2.3 million each.

The city council has since assured that the bungalows are safe for occupation while the caved-in road has been repaired.

In 2013, a similar landslide happened some 200m from that location.

The NCPR is being built by the contractors of the undersea tunnel as part of a three-road bypass side project. It will connect Teluk Bahang, Batu Ferringhi and Tanjung Bungah.

This is separate from another highway project pursued by SRS Consortium for the Penang government.

The NCPR will mostly be on the road level with 2.275km as an elevated stretch which requires cutting the untouched hills of Tanjung Bungah and Teluk Bahang.

Residents have objected to the project, citing a variety of reasons including traffic and noise pollution. However, they are mostly concerned over the hill cutting and the permanent damage this will bring to the forests there.

According to the NCPR’s environmental impact assessment (EIA), 46% of the bypass will be on terrain with a higher than 25-degree slope. NGOs have argued that slopes above 25 degrees are usually “sensitive hill lands”.

Despite heavy opposition from residents’ associations, NGOs and other groups, the project was given approval by the Department of Environment (DoE) last November.

The contractors have vowed to follow 59 strict conditions imposed by the DoE and the project owner, the Penang government, has promised to stop the project if these conditions are not met.

The project is scheduled for completion in the next seven years, pending completion of other bypass roads in the RM6.3 billion Penang undersea tunnel and three main roads project.

Kam said while there was no doubt that engineering methods, mitigation and other ways might be proposed to ensure that all goes well in the road project, Malaysia’s track record in doing so had not been stellar.

“What is the track record in terms of developers and authorities being able to follow these conditions and guidelines?”