It is not that difficult to predict which areas of Penang Island are most prone to landslides with a high degree of accuracy (almost 80%). The research has been done.
Red – Highly hazardous areas
Green – Hazardous
Blue – Moderately hazardous
White – Not hazardous
This map of Penang Island was published in a paper titled “Landslide Hazard Mapping of Penang Island Using Poisson Distribution with Dominant Factors” written by Lea Tien Tay, Mutasem Sh. Alkhasawneh, Habibah Lateh, Md Kamrul Hossain, and Anton Abdulbasah Kamil from USM’s Engineering Campus and its School of Distance Education. The paper was published in the Journal of Civil Engineering Research in 2014 – three years ago.
The map is based on 11 dominant factors (selected from 22 factors) responsible for landslides. According to the researchers the 11 factors are distance from drainage, rugosity, height, slope gradient, diagonal length, surface area, distance from fault line, rain, aspect, geology and soil texture.
In an earlier paper “Probabilistic landslide hazards and risk mapping on Penang Island”, published in the Journal of Earth System Science in 2006, researchers Saro Lee of the Korea Institute of Geoscience and Mineral Resources and Biswajeet Pradhan compared landslide location data with a probabilistic model and found an accuracy of 80%.
This was one of the maps included in their paper:
Besides this, the following is an easy-to-understand video explaining the safety factor of slopes, which is a function of resistance force of the slope compared to its driving force. The video shows, among other things, that slope stability is more sensitive to the water content in the soil rather than soil cohesion.
In the Chee Seng Garden of Tanjung Bungah, some have heard the sounds of water coming from the slopes above. One resident described this as the sound of a waterfall. It is believed that are a number of hidden streams and small rivers on the hills in Tanjung Bungah. What happens if any of these streams are obstructed or diverted by development projects on the slopes?
As a parting note, take a look at these two incidents of what happens when risk factors have not been fully understood:
Check out the almost vertical slopes behind this row of houses in Tanjung Bungah. And what driving force pressured the road to collapse? Was there a stream on the slope behind this row of houses?
And here is what happens when streams or drains are diverted by hill-slope projects: