Landslide: Man-Made Failure Due To Emphasis On Development Projects

Man-Made Failure Due To Emphasis On Development Projects

Landslides have posed serious threats to settlement and structures that support transportation, natural resource management and tourism. More than 100 hillslopes had been identified by Malaysian Public Works Department (PWD) as risky for possible landslides (Mukhlisin et al., 2010). Gue and Tan (2006) in the study of causes of slope failure found that eighty-eight percent of the 49 cases of slope failure in Malaysia are man-made slope failures. The failures are mainly due to the either design errors or construction errors. The finding was supported by Jamaluddin (2006) who studies on many cases of slope failures in Malaysia indicated that the slope failures are mostly attributed to human factors such as negligence, incompetence, lack or poor maintenance system, ignorance of geological inputs, unethical practice and various negative human attitudes.

According to the National Slope Master Plan (2009), the main contributing factors to trigger the landslides are found to be geological causes or ground conditions, hydrological causes, morphological causes, physical causes and human causes. These main contributing factors are based on the review of selected worldwide literatures. A total of 30 case studies excluding Malaysia case studies were carried out with reference from countries such as China, Italy, Thailand, Russia, Taiwan, Germany, Korea, Japan, and Australia. The statistics indicate that ground conditions and human causes are the major contributing factors of landslide failures on a worldwide basis. In addition, the occurrence of landslides also due to mismanagement of land use due to the increasing number of population and the needs of land for producing agricultural products that, that force people to stay in landslide hazard areas (Soralump, 2010).

Gue and Tan (2006) found that most of the slope failures in Malaysia are due to design errors, construction errors, design and construction errors, geological features and maintenance. The study is based on 49 investigation cases of primarily large landslides on residual soils.

Causes of Landslides	Numbers of Cases	Percentage (%)
Design Errors	29	60
Construction Errors	4	8
Design & Construction Errors	10	20
Geological Features	3	6
Maintainance	3	6
Total	49	100

Table 1 Causes of Landslides (After Gue & Tan, 2006)

The results of the study indicate that 60% of the failures are due to inadequacy in design alone. The inadequacy in design is generally the result of a lack of understanding appreciation of the subsoil conditions and geotechnical issues. Failures due to construction errors alone either of workmanship, materials and/or lack of supervision contributed to 8% of the total cases of landslides. About 20% of the landslides investigated are caused by a combination of design and construction errors. For landslides in residual soil slopes, the landslides caused by geological features only account for 6% which is same as the percentage contributed by a lack of maintenance (Gue and Cheah, 2008).

National Slope Master Plan (2009) also has similar study after Gue and Cheah (2008). The causes of landslides can be due to the abuse prescriptive methods, inadequate study of past failures, design errors including insufficient site specific ground investigation. However, lack of appreciation of water such as underestimating existing groundwater table and inadequate capacity of surface drainage is also one of the factors causing the landslides. A guideline from government agencies like Minerals and Geosciences Department and Department of Town and Regional Planning stated that the degree of risky hilly area starts at 25 degree. Besides, the hilly area with intrusive acid rock gives higher probability to cause a slope failure (Mukhlisin et al., 2010).

Farisham (2007) has carried out the study on rapid landslide occurrence at the hillside development areas, in the Klang Valley. The study was focused on the architectural approach, the theory and the practice in the hillside development, aspects to be considered by the architect, in proposing the site layout. The study found that the occurrences of landslides in Klang Valley are due to the design and construction failure of the retaining wall, lack of maintenance and triggering by rainfall. In addition, Farisham (2007) concluded that understanding on original terrain is very important; site layout proposal must be done through detail site investigations. The selected design approaches and method of construction for hillside development have given major impact on the safety of the development. Therefore, the hillside area must be designed and constructed, with proper understanding and should be responsive to the natural terrain, in order to protect the stability of the land due to the fact that when the land stability is low or bad the chances of landslide occurrence is very high.