PETALING JAYA: While heavy rain is the most visible culprit behind slope failures, the Works Ministry has warned that it is not the only trigger.
Minister Datuk Seri Alexander Nanta Linggi (pic) said there are hidden hazards lurking beneath the ground that could trigger landslides.
“Rainfall is a major trigger but it is not the only one. Water leakage from underground utilities, poor drainage, erosion, construction activities and changes to the surrounding ground conditions can also contribute to instability.
“The Public Works Department’s (JKR) National Slope Master Plan identifies rainfall and groundwater rise, leakage of buried water services, erosion and adverse human activities as among the important triggering or contributory factors,” he said in an interview.
Nanta said JKR’s slope maintenance guideline specifically identifies abnormal leakage, widening cracks, settlement and bulging or distortion of retaining structures as conditions requiring prompt engineering attention.
A recent incident in Cheras, where residents were evacuated following a landslip near their flats due to a leaking underground pipe, has put the spotlight on the danger of water leakage beneath the surface.
Stating that the ministry continuously monitors 34,544 slopes nationwide, he said suspicious slopes should be reported to the authorities immediately.
“If several warning signs appear together, especially during heavy rainfall, the public should keep away from the affected slope and immediately inform the relevant authorities.
“Slope management is carried out throughout the year but our level of preparedness is increased during periods of prolonged or intense rainfall, particularly when weather warnings are issued.
“Higher-risk and critical slopes are given greater attention, particularly during periods of adverse weather. This includes enhanced surveillance, emergency patrols, inspection of drainage systems, observation of surface erosion and groundwater seepage and checking for any signs of ground movement.
“One of the most important factors during heavy rainfall is water. Prolonged rainfall can saturate the soil, increase groundwater levels and pore-water pressure, reduce soil strength and eventually trigger slope movement,” he said.
“Therefore, our inspection does not focus only on the physical condition of the slope, but also on how water is entering, flowing through and leaving the slope.”
Currently, JKR monitors 27,216 slopes in Peninsular Malaysia, 4,178 in Sabah, 2,969 in Sarawak and 181 in Federal Territory of Labuan.
JKR director-general Datuk Ibrahim Esa said there are warning signs the public should look for especially during or after a prolonged heavy rainfall.
“Among the more important signs are new cracks or rapidly widening cracks on the ground, roads, pavements or drains; cracks, tilting or bulging of retaining walls; localised settlement or sinking of the ground; new or unusually strong water seepage from a slope or retaining wall; muddy water emerging from the slope; overflowing, damaged or blocked drains; leaning trees, fences, lamp posts or other structures; small falls of soil, rocks or debris from the slope; or sudden erosion or formation of depressions near the slope.
“In serious situations, the public should look for unusual sounds associated with ground or structural movement,” said Ibrahim.
Currently, there are 73 rain gauge stations installed nationwide, comprising 41 in Peninsular Malaysia, 19 in Sabah, 11 in Sarawak and two in Labuan.
In addition, three Robotic Total Stations and one Global Navigation Satellite System have been installed at Sections 44 and 46 of the Simpang Pulai-Gua Musang Road to monitor slope movement.
