Lojing: The second and final article in this two-part report explores the expertise and technology behind the construction of the Lojing Sabo Dam, including how its location and design were determined, the use of technology, as well as monitoring and maintenance measures to ensure the structure's long-term effectiveness.
According to BERNAMA News Agency, the damage visible on a road may merely be the final manifestation of a threat that began much further upstream. In Lojing, heavy rainfall can trigger the movement of water together with soil, rocks, timber, and debris from slopes before the flow converges towards Federal Route FT185, as occurred on January 3, 2021, causing extensive damage at Section 61 of the Lojing-Gua Musang Road.
The incident prompted the Public Works Department (JKR) to review its mitigation approach, as merely repairing damage downstream would not be a comprehensive solution if the threat upstream remained unaddressed. Based on technical assessments and the success of three previous projects, JKR identified the Sabo Dam approach as the best solution and decided to construct one at Section 61 of the route.
JKR director-general Datuk Ibrahim Esa stated that the construction of the project was fully completed on July 14, 2026, after being carried out for 13 months from June 18, 2025. 'The main rationale for its implementation is to provide a long-term solution or mitigation against debris flow risks that could affect the safety of road users, infrastructure, and the accessibility of Federal Route FT185,' he told Bernama.
The nearly RM11 million project involves more than just the construction of a single structure. It is a comprehensive mitigation and rehabilitation package comprising a Sabo Dam, debris flow barrier, slope repair and strengthening, drainage systems, pavement works, road rehabilitation, and utility relocation. The project also involved the acquisition of about 1.7 acres of land to provide sufficient space for the entire mitigation system to be developed more effectively.
Sabo Dam is a Japanese technology, with 'sabo' referring to sand control. In Malaysia, the Lojing Sabo Dam is the fourth such structure in Peninsular Malaysia, after those in Raub, Pahang; Seremban, Negeri Sembilan; and Baling, Kedah. However, the project adopts a distinct approach by integrating several components into a layered protection system.
Ibrahim explained that the decision to construct the Sabo Dam was made following a technical assessment that considered the history and causes of previous incidents, the valley-like terrain between two slopes, the presence of debris materials upstream, and the road's exposure to flows during heavy rainfall. 'The Lojing Sabo Dam adopts an integrated approach, combining the Sabo Dam, debris flow barrier, slope repairs, and drainage system as a layered protection system,' he said.
The main function of the Sabo Dam is to control the movement of sediment and debris from upstream areas, slow the flow, and reduce its impact energy before it reaches downstream areas. During heavy rainfall, water flowing from higher ground can carry soil, sand, rocks, large boulders, timber, and other debris. The Sabo Dam helps trap or retain some of these materials, while the debris flow barrier provides an additional layer of protection to trap rocks, timber, and debris.
The combination is intended to reduce the amount and size of debris reaching the road, minimize the impact on roads, bridges, and drainage systems, and reduce the likelihood of roads being buried or cut off. However, the structure is not designed to stop landslides at their source. Slope instability risks are addressed through slope rehabilitation and drainage management, while the Sabo Dam and debris flow barrier control materials that have already moved downstream.
Behind what appears to be a physical solution, the actual engineering work begins much earlier, determining where the structure should be built and how it should function under real-world conditions. Director of JKR's Slope Engineering Branch Mohd Shaifuddin Abdul Razak said the location of the Sabo Dam was selected based on topographical, geological, and hydrological studies, as well as analysis of debris flow paths.
'For the FT185 Section 61 area, the technical assessment found that the terrain resembles a valley between two slopes, with limited vegetation cover. This combination increases the likelihood of rainwater and loose materials from upstream areas converging along the route and moving towards the road during heavy rainfall,' he said. He noted the location also had a history of serious landslides and debris flows in 2021, which affected the FT185 route.
JKR's approach to disaster risk management has also evolved alongside the use of monitoring technology. Mohd Shaifuddin said JKR is using and expanding the use of technology in slope management and monitoring according to the level of risk and requirements of each location. These include the Landslide Early Warning System, rainfall monitoring, slope movement monitoring, as well as geotechnical and surveying instruments.
Although the project has been completed, JKR cannot yet claim a specific level of risk reduction, as the Sabo Dam only began operating on July 14, 2026. The monitoring period is still too short to draw statistical conclusions based on actual performance. Mohd Shaifuddin said its effectiveness would need to be assessed using field data over a longer period, particularly after several episodes of heavy rainfall and during the monsoon season.
Another less visible challenge is ensuring that the Sabo Dam continues to function after construction machinery has left the site. The structure is designed to trap sediment, rocks, timber, and debris. Therefore, accumulated materials must be inspected and removed once they reach a level that could reduce the structure's effective capacity. Maintenance includes regular inspections as well as special inspections following heavy rainfall or extraordinary events.
From an economic perspective, the Sabo Dam cannot be assessed solely based on its construction cost. According to JKR, preventive and mitigation measures can be more economical in the long term compared with repeated repair works, but the assessment must be based on life-cycle costs. Costs that can be avoided include repairs to roads and bridges, debris removal, emergency mobilization, losses resulting from road closures, as well as additional travel time and costs.
The Sabo concept has a long and well-established history in Japan, which is among the leaders in sediment disaster management. However, the basic principles of the technology do not mean that designs from Japan can simply be applied wholesale in Malaysia. JKR has adapted the technology to local geology and soil types, terrain, catchment characteristics, tropical rainfall intensity, the expected volume and size of debris, the location of roads and bridges, available construction materials, as well as operational and maintenance requirements.
Ibrahim stated the Lojing project has the potential to become a reference model as it demonstrates a shift in approach - from merely repairing roads after disasters to managing risks upstream before debris reaches infrastructure. However, the approach cannot be directly applied to all highland areas. Each location has different geological conditions, rainfall levels, catchment sizes, types of debris, terrain, and assets that need to be protected.