Hill slope development feasible

NST 2010/07/29


THE public, especially those living on hill slopes and elevated areas, must be more aware of issues such as soil erosion and drainage to ensure their safety and prevent untoward incidents.

International Research Centre on Disaster Prevention (IRCDIP), Faculty of Civil Engineering, Universiti Teknologi MARA director Prof Dr Roslan Zainal Abidin says this is crucial as a monitoring system would provide early warnings to the public.

"People fear living on slopes as there have been many cases of disasters in those areas. But with the right knowledge, living on hill slopes can be safe."

Roslan believes the best way to educate the public on matters pertaining to hill slopes would be through roadshows or public meetings between residents, the local authorities and related agencies.

"This is also the quickest and most efficient method. They can gather the residents during the weekends and go to a nearby hillside and brief them on what to look out for.

"This way, the public will be able to give their feedback to the authorities in the event there is soil or land movement owing to heavy rainfall, or if there are early signs of erosion in their areas," he adds.

One of the most basic things that residents can look out for is erosion.

Roslan says erosion patterns are an early indicator of soil movement in the area.

Additionally, simple things such as being aware of blocked drains and observing soil texture are also part of an early monitoring mechanism.

Roslan says at present, the regulations and requirements for building on hill slopes are sufficient but as with all projects, there must be ample monitoring before, during and after the development was completed.

"Rules and regulations must be adhered to and enforced," he says, adding that all technical agencies involved must also play their role to ensure early detection of any potential disasters.

"There is no reason why hill slopes cannot be developed, provided the area is thoroughly assessed and the level of risk identified."

At each level of risk, there is an appropriate engineering solution to ensure the safety of the development project.

Kumpulan Ikram Sdn Bhd's head of Geotechnical Forensic Unit, Mohd Taufik Haron, says all hill slopes and elevated areas must be assessed holistically, taking into account many factors that were inter-dependent.

He adds that local authorities should advise house buyers before they make their decision on whether to buy properties near hill slopes.

"This is necessary so as to restore public confidence. This assures the public that the government is performing its duty."

Generally, slope failure in Malaysia is not only caused by slope geometry (for example, slope gradient more than 35 degree) but also other factors as well, such as soil and rock engineering properties, drainage system, ground water table, geological factor, and rainfall intensity.

Therefore, to minimise the potential of landslides, the above mentioned contributing factors should be considered as a holistic approach.

In the meantime, says Taufik, the community plays an important role in helping to prevent or reduce landslide risk, in that they have a choice to either live in mountainous areas or in a "safer" location.

However, for those already living on hillsides, they do not have to worry if the developers have started developing the second phase of the highlands, as a rigorous approval process would have already been undertaken by them and the local authorities.

At present, development is allowed for hill slopes and elevated areas only if four criteria are met, which are location, land use, intensity (density, plinth and plot ratio) and adherence to all required guidelines by the technical agencies involved.

The sensitivity of an area environmentally is also taken into account. The more elevated an area, the more the sensitivity level increases, thus limiting development.

For areas with mixed classes of elevation, the developer must apply for exemptions and can proceed only after meeting the more stringent engineering requirements.

The developer must also appoint an independent assessor to check its design and monitor the pre- and post-construction works to ensure that the buildings are safe.

At the local government level, the process of application for the development of hill slopes and elevated areas must be coordinated by the one-stop centre to allow ease of legal and technical matters between the agencies involved.

"Man-made slope disasters can be minimised by focusing on three technical phases, namely planning, during construction and post-construction activities.

In the "planning phase", the submitting engineers have to undertake a detailed investigation in a holistic manner, as mentioned previously.

"In terms of approval, developers have to go through a very difficult process because when a decision is made, it is actually not by any single party."

A "hillside development technical committee" will be formed at the local authority level and comprise related government and technical departments, including the Town and Country Planning Department, Public Works Department, Department of Irrigation and Drainage, Tenaga Nasional Berhad, Environment, Mineral and Geosciences Department and the Agriculture Department.

Their opinions will be sought before approval for any hillside development is given.

Under the "during construction phase", periodic supervision by the authority should be implemented to ensure that the construction is executed according to the design requirements and aspects.

In the "post-construction phase", monitoring of instrumentation and periodic slope maintenance should be carried out. By having proper slope maintenance, the signs of slope instability can be detected earlier and minor slope repair can be done, thus minimising the risk of large-scale slope failure.

"The cost of major slope repair is much more expensive that carrying out maintenance works," says Taufik

Ever since the Bukit Antarabangsa landslide tragedy on Dec 6, 2008, people have learned that hill slopes are classified according to varying gradients.

The Federal Government also unveiled the Guidelines for Hillside and Highland Areas Development Planning last year, with provisions to manage hill slope developments.

Among others, the guidelines ban building activities on slopes of more than 35 degrees. Also disallowed are projects on slopes of between 15 and 35 degrees that display signs of erosion, land instability or laden with sensitive geological material.

All development applications must be accompanied by a technical report by a registered engineer.

Slopes have been classified into four classes and four levels of height. Class 1 is for slopes of less than 15 degrees; Class 2 for slopes of between 15 and 25 degrees; Class 3 for slopes of 25 to 35 degrees; and Class 4 where slopes are more than 35 degrees.

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