SINERGI Vol. 29, No. 3, October 2025: 599-614
http://publikasi.mercubuana.ac.id/index.php/sinergi
http://doi.org/10.22441/sinergi.2025.3.004

A review of rock slope failures in Malaysia: exploring types,
cases, causes, and consequences
Aidatul Izana Mohd Taha1,2, Nazirah Mohamad Abdullah3*
1

Faculty of Civil Engineering and Built Environment, Universiti Tun Hussein Onn Malaysia, Malaysia
Department of Polytechnics and Community College Education, Ministry of Higher Education, Malaysia
3
Faculty of Applied Sciences and Technology, Universiti Tun Hussein Onn Malaysia, Malaysia
2

Abstract
Rock slope failures remain a significant concern in regions of
Malaysia with varying geological formations. This review examines
the challenges posed by these incidents and addresses key
knowledge gaps. By providing a comprehensive, multidisciplinary
analysis of case studies, technological advancements, climate
influences, disaster management, and socio-economic impacts, it
offers valuable insights for researchers, engineers, and
policymakers. It examines key failure types, including rock falls,
slides, avalanches, and general failures, through notable case
studies such as Bukit Lanjan (Selangor), Kinta Valley (Perak), and
Mount Kinabalu (Sabah). A comprehensive methodology framework
was employed, utilizing manual search techniques (handpicking,
snowballing, citation, and reference tracking) alongside advanced
keyword-based searches with Boolean operators in Scopus,
ScienceDirect, and Google Scholar databases. Findings reveal that
Malaysian rock slopes are highly susceptible to collapse due to
heavy rainfall, human activities, and natural events such as
earthquakes. While these factors can act independently, their
combined effects significantly amplify failure risks, particularly during
intense rainfall. The consequences extend beyond immediate
casualties, injuries, and property damage, leading to infrastructure
failures, economic disruptions, and environmental degradation. This
review underscores the need for sustainable mitigation strategies to
address these risks and highlights the urgency of implementing
effective solutions to safeguard lives, infrastructure, and ecosystems.

Keywords:
Rock avalanche;
Rock slide;
Rock slope failure;
Rockfall;
Slope failure;
Article History:
Received: August 28, 2024
Revised: February 22, 2025
Accepted: March 10, 2025
Published: September 1, 2025
Corresponding Author:
Nazirah Mohamad Abdullah
Faculty of Applied Sciences and
Technology,
Universiti Tun Hussein Onn
Malaysia, Malaysia
Email: nazirah@uthm.edu.my

This is an open-access article under the CC BY-SA license.

INTRODUCTION
Complex and uncertain natural disasters
cause profound effects on the human population.
A significant geological hazard example is
landslides, which produce high fatalities annually.
Hence, this phenomenon emphasizes the crucial
requirement for improved forecasting and
prevention methods. Landslide susceptibility is
also closely associated with natural slope
instability, existing geological vulnerabilities, and
human-induced modifications (cut slopes) [1].

Recent studies provide comprehensive insights
into this phenomenon across different regions,
emphasizing the importance of robust prediction
models and prevention strategies. For instance, a
study in Ambon City, Indonesia, evaluated factors
such as slope inclination, rainfall, and rock type
(related to weathering), producing a landslide
vulnerability map that aids in slope management
[2]. In Turkey, researchers utilized GIS and
frequency ratio methods to assess landslide
susceptibility, identifying geology, slope, and

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proximity to rivers as key factors [3]. Similarly, in
India, logistic regression models were used to
understand the impact of anthropogenic activities
on slope stability, highlighting the role of rainfall
and soil type [4].
These determinants predominantly facilitate
the pervasive incidence of rock slope failures,
representing a crucial concern within geology and
environmental sciences. The manifestation of rock
slope failures in Malaysia presents considerable
hazards to infrastructure, the safety of individuals,
and the ecological balance. These failures, often
triggered by geological, hydrological, and
anthropogenic influences, have been documented
across diverse regions, particularly in locales
characterized by steep inclines and extensively
weathered rock formations. The abrupt and
potentially disastrous collapses of rock masses
substantially influence natural landscapes and
human
undertakings.
This
phenomenon
predominantly transpires in areas exhibiting a
variety of geological configurations [5, 6, 7]. Rock
slope stability is essential due to its direct
influence on infrastructure safety and durability,
and slope failures can lead to severe outcomes.
These outcomes include significant financial
losses,
permanent
environmental
harm,
destruction of essential infrastructure, increased
safety risks, and significant disruptions to
transportation systems [5][7].
Previous studies have examined rock slope
stability from different perspectives. Kinematic
analysis is a prevalent technique for evaluating
potential failure modes in rock slopes, particularly
within limestone terrains [8][9]. Numerical
modeling, incorporating probabilistic techniques,
assesses slope stability across varying conditions,
including seismic events and failures prompted by
rainfall [8][10]. In Malaysia, rock slope stability
assessments have conventionally depended on
kinematic analysis and rock mass rating
frameworks. Nevertheless, there is an emerging
trend towards adopting numerical methods to
enhance precision and dependability [7][9]. An
examination of 39 case studies within Malaysia
showcases the progression from rudimentary
kinematic evaluations to advanced numerical
analyses, indicating a growing comprehension of
rock mechanics [7]. The technical orientation of
current studies frequently overlooks the broader
ramifications of rock slope failures, particularly
their influence on disaster risk management and
policy formulation [7]. A systematic review is
needed that weaves technical evaluations and
incorporates socio-economic dimensions and
policy ramifications, especially in regions like

600

Malaysia, where urban expansion intrudes upon
hillside territories [7].
The Malaysian terrain, characterized by
deep tropical weathering, poses significant
challenges for infrastructure development. This
complexity arises due to a combination of steep
slopes, high rainfall, and diverse geological
formations, which increase the risk of landslides
and ground instability. According to a study on
Malaysian infrastructure, the government faces
numerous challenges in recognizing and
measuring infrastructure assets due to the unique
features of the terrain, such as long useful life and
being part of an asset system or network [11].
Additionally, the Rapid urbanization and extensive
transportation network development in Greater
Kuala Lumpur, including the Klang Valley,
complicate infrastructure development and
necessitate advanced planning and management
for sustainable growth, as evidenced by concerns
over urban sprawl and the need for efficient land
use and transit-oriented development [12].
Advanced
technologies,
such
as
Unmanned Aerial Vehicles (UAVs) and Light
Detection and Ranging (LiDAR), have shown
promise in improving infrastructure project
outcomes. UAVs offer benefits in surveying and
monitoring, but their implementation faces barriers
such as regulatory restrictions, industry
reluctance, and technical challenges related to
data acquisition and quality control. Effective
utilization of UAVs could greatly enhance
construction efficiency and safety, provided these
challenges are addressed [13]. Similarly, LiDAR
technology provides highly accurate terrain
mapping capabilities; however, its adoption in
Malaysia remains limited due to several
constraints. These include challenges in data
processing and filtering that may result in
mismatches, the absence of standardized
operational procedures, and a range of technical
as well as financial barriers that collectively hinder
its large-scale integration into infrastructure
projects [14]. In addition to technological
challenges, Malaysia's construction industry must
adapt to demographic changes, such as an aging
population. This demographic shift impacts
building design, workforce dynamics, and
construction. Preparing for an aging nation
involves ensuring that infrastructure is accessible
and suitable for senior citizens, which requires
additional costs and modifications to current
construction practices [15]. The combined effect of
these factors underscores the complexity and
urgency of addressing infrastructure development
challenges in Malaysia’s diverse and rapidly
changing landscape.

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This paper reviews documented rock slope
failures in Malaysia, categorizing them by type and
examining their causes and consequences. It
integrates geotechnical, environmental, and
socio-economic
perspectives
to
develop
comprehensive strategies for mitigating these
failures. Furthermore, the review aims to bridge
these gaps by providing a comprehensive
overview, covering case studies, technological
advances, climate effects, disaster management,
and
socio-economic
impacts.
This
multidisciplinary approach offers valuable insights
for policymakers, engineers, and researchers in
rockfall hazard management.
Government Policies for Slope
Malaysia has initiated the National Slope
Master Plan 2009–2023 (NSMP) [16] in response
to the significant increase in slope-related
disasters. This plan provides a comprehensive
framework to reduce landslide damages
nationwide by equipping key authorities with the
essential tools and information for all phases of the
disaster management process. Additionally, key
authorities are provided with instructions and
concrete resources to enhance their emergency
preparedness, response, and recovery capacity.
For example, 3D scanners can improve search
and rescue, easing rugged terrain-based travel
and victim identification. This plan can also
establish numerous provisions, such as slope
management
procedures
integrating
riskreduction strategies and improved infrastructure
development. Hence, failures are effectively
prevented when addressing issues related to
slope-related disasters.
The vulnerability of Malaysia to various
natural disasters (floods, landslides, and
earthquakes) has been acknowledged in the
Twelfth Malaysia Plan 2021–2025 (RMKe-12)
[17]. Consequently, disaster risk management
(DRM) at the national policy level has been
elevated to a prominent position. This feature aids
in safeguarding the capabilities and infrastructure
of Malaysian individuals. A detailed structure
concerning proactive strategies is also outlined in
the DRM of the RMKe-12. These approaches
include early warning technologies and
community readiness-related programs in
constructing vital infrastructure for disaster
prevention measures. For example, these
methods are utilized in designing and constructing
important structures (buildings and highways).
This plan also focuses on capacity building,
training, and providing resources to local

authorities with emergency responders to handle
crisis scenarios successfully.
The 2023 Mid-Term Review [18] of the
RMKe-12 has highlighted the dedication of the
Malaysian government to landside disaster
management prevention using two key initiatives:
a landslip early warning system and a National
Geological Disaster Centre. Approximately RM
563,000,000 has also been allocated in the 2024
Malaysian budget to enhance landslide readiness.
This allocation signifies the significant dedication
of the Malaysian government to take preemptive
actions to restore and stabilize more than 2,000
high-risk slopes and implement improved
monitoring and preventive actions [19].
METHOD
This review initially evaluated relevant
studies to identify the correlations between rock
slope failure and factors affecting rock stability in
Malaysia. A study by [20] proposed using several
search algorithms to improve the likelihood of
discovering related studies. The study revealed
two primary search techniques: manual
(handpicking, snowballing, citation tracking, and
reference tracking) [20][21] and advanced
techniques [constructing queries or search strings
using Boolean operators in multiple databases
(such as Scopus and Web of Science)] [22][23].
Meanwhile, [24][25] created a Literature Review
Protocol (LRP) detailing databases, languages
covered, keywords, and search methods.
The relevant studies in this review were
initially retrieved from numerous search engines
(Science Direct, Scopus, Google Scholar,
Mendeley, and the databases of the University for
journals, books, and proceedings). Several
Boolean operators ("OR", "AND", and "NOT")
were then employed to integrate multiple related
terms for targeted search results ("Factor", "Rock
slope failure", "Rock slope instability", "Cliff
collapse", "Slope failure", "Rock Fall", "Rock
Slide", "Rock Avalanches", and "Malaysia"). This
review also broadly examined studies from the
past 20 years, focusing on slope stabilization
procedures in Malaysia and Southeast Asia.
Subsequently, the data were gathered from their
websites or portals for statistical reference. The
inter-library lending and document delivery service
of the University was also utilized for offline and
closed-access
articles
employing
manual
methods. Even though the search process in this
review yielded numerous articles, only the most
pertinent English studies were used.

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Case Study for Rock Slides
The predominant rock slope instability type
in Malaysia is rock slides. This instability occurs as
sliding movements along discontinuities in rock
masses and is categorized based on the motion
and fracturing of the rock mass. Numerous
movement sub-types are observed in the slide,
such as rotational, planar, wedge, compound, and
regular slides. A study by [26] grouped these
slides based on their speed, rock characteristics,
and
movement
patterns.
Recent
field
investigations and kinematic analyses show that
discontinuity geometry and basal rupture
architecture fundamentally control rock‐slope
failure modes and their velocities.
i.Rotational slides: Slow movement on a curved
base, causing the rock mass to rotate forward
[26][27].
ii.Planar slides: Sliding on a flat plane that
daylights; occurs when the slope is steeper than
the plane’s resistance [26, 28, 29]
iii.Wedge slides: A triangular wedge formed by
two planes slips downslope along their
intersection, often rapidly [26][28].
iv.Compound slides: Movement along several
connected surfaces, so different parts travel at
different speeds [26].
v.Irregular slides: Failure follows a rough,
discontinuous fracture path, with sudden bursts
often triggered by water pressure [26][27].
Another study by [7] conducted a study
defining a rock slide as an abrupt and frequently
unforeseeable occurrence in which substantial
rock masses detach and slide down slopes.
Nonetheless, these descriptions were simplified,
and real-world rock slides could be more intricate.
The intricacy of real-world rock slides is
highlighted through various case studies and
analyses that reveal the complexities beyond
simplified
descriptions.
For
instance,
investigations of rock slides in British Columbia
that evolved into flow-like landslides highlight the
dynamic nature of debris avalanches and flow
deposits influenced by ground saturation levels
and topographic gradients [30]. Additionally,
discussions on advanced monitoring and
modeling techniques for rock structures
emphasize technological advancements in
understanding rock mass stress and deformation
[31]. Furthermore, examinations of the hydrology
of active rock glaciers in the Austrian Alps
demonstrate the impact of weather conditions and
meltwater flow on rock glacier discharge patterns
[32]. Figure 1 illustrates two sliding failure types on
rock slopes: a planar sliding failure observed in an
abandoned quarry and a wedge sliding failure on
a road-cut slope.

602

Figure 1. (a) The observed sliding failure on a
rock slope (including planar sliding on an
abandoned quarry) and (b) the wedge sliding on
a road-cut slope [7].
The rock layers were shifted along a noticeable
plane, implying their planar nature (see Figure
1(a)). Meanwhile, the rock displacement occurred
along two parallel planes, creating a wedge (see
Figure 1(b)). Thus, these images aided in
classifying the typical rock slope failures.
On November 26, 2003, Malaysia
experienced a rock slide at the 21.8-km point of
the Bukit Lanjan Interchange on the New Klang
Valley Motorway (NKVE. This area falls within the
authority of the Petaling Jaya district in Selangor,
Malaysia. Approximately 35,000 m3 of rock debris
fell onto the motorway and blocked the road,
mainly comprising different angular block sizes. A
study by [33] documented that the rock slope
failure in Bukit Lanjan was attributed to geological
conditions and triggering events. The study
revealed that the pre-existing rock mass structure
containing steep-dipping faults and unfavorable
joint orientations contributed to instability.
Conversely, the extended period of heavy rainfall
likely triggered the incident.
The failure is confirmed to be caused by a
large wedge block formed by the intersection of
three key planes as follows [33][34]:
i. A steeply dipping fault plane F1 (dip/dip
direction: 80o/225o)
ii. A gently dipping joint plane J1 (dip/dip
direction: 60o/070o)

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iii. A released plane F2 (dip/dip direction:
78o/327o)
The factor of safety (F.O.S.) also decreased
below 1 when simulated water-filled faults and
joints from the hydrostatic pressure conditions
were integrated into the analysis, suggesting
imminent failure. Therefore, the significant impact
of high-water pressure on this occurrence was
demonstrated. This outcome was reinforced by
the unusually high rainfall in November 2003,
surpassing records dating back to 1966 [33].
Although the Bukit Lanjan incident did not cause
fatalities, the economic repercussions were
significant. Figure 2 portrays the massive granite
boulders completely obstructing the NKVE
highway due to the failed rock mass [33]. This
incident cost the Malaysian government
approximately RM 836,000,000 (economic cost)
due to lost revenues and required corrective
actions [16]. The extended traffic disruptions
resulting from this incident also substantially
impacted businesses and residents in the Klang
Valley, exacerbating the economic strain.
Figure 3 depicts a detailed timeline of the
Bukit Lanjan rockslide incident and the following
rehabilitation actions. The initial image depicted a
peaceful green mountainside before the rockslide
incident, showcasing stability and lush vegetation.
Subsequently, the second image highlighted the
immediate aftermath, displaying major collapse
and scattered debris, modifying the terrain. The
third image then conveyed the beginning of repair
work, featuring machinery and terracing efforts to
stabilize the hillside.

Figure 2. The rock slope failure incident at the
Bukit Lanjan Interchange (KM 21.8 of NKVE) on
November 26, 2003. The entire expressway was
closed to the public due to the failure of materials
obstructing the road [33].

Figure 3. A detailed Bukit Lanjan rockslide
incident and the corresponding repair efforts [16]
Likewise, the fourth image demonstrated
continued advancements in the restoration
process involving enhanced terracing and erosion
prevention methods. Finally, the fifth image
presented the finished repair work, featuring
clearly defined terraces, regrown flora, and
preventive measures (stabilizing nets to reduce
the risk of future landslides). This process
indicated a successful restoration of the site.
Case Study for Rock Falls
Compared to rock slides, which typically
entail large-scale mass movements, the
detachment and descent distinguish rock falls
from the bounce of individual rock or ice fragments
[35]. Despite this phenomenon frequently
occurring individually or in clusters, the pieces in
motion primarily interact with the ground rather
than with one another, resulting in minimal
fragmentation. Generally, rock falls contain small
amounts of debris [35][36]. Nonetheless, this
phenomenon can present substantial dangers
owing to its rapid speed and erratic paths. Even
though slopes are prone to rock falls, natural rock
faces in karst landscapes are commonly affected
by weathering and erosion, causing discontinuities
[37].
The NSMP has stated that the rapid
development in Perak (Ipoh area) has led to higher
land demands. This finding has resulted in

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residential and industrial buildings near steep
limestone cliffs [16]. A study by [7][38] noted that
considerable advancements occurring near
certain limestone hills were observed. The study
revealed that residential areas with industrial
complexes and temples were situated near the
hills. Quarrying processes were also ongoing to
extract high-quality limestone aggregates in the
limestone hill regions. Thus, multiple rockfallrelated incidents were documented in the Kinta
Valley between 2004 and 2023.
Table 1 shows that between 2004 and
2023, the Kinta Valley, Perak, Malaysia,
experienced multiple significant rockfall incidents,
highlighting the hazards presented by its
limestone-dominated landscape. Casualties and
damage effects from events like the 2004 Mount
Bercham rockfall and the 2006 Mountain Pass
failure, which highlighted deployment scales of
catastrophic collapses, present an important risk
to life and property. Adding to the public threat, the
2008 Gunung Karang Besar rockfall halted
transport, and since then, significant structural
damage near services such as the Yee Lee Edible
Oils Factory and quarry-related deaths in 2019
stress the occupational danger. Such active and
passive monitoring technologies capable of
carrying out 3D modeling and lineament density
studies can be implemented in areas at risk and
highly prone to landslides, which would've been
used in recent deaths and damage cases such as
the 2022 rockfall incident in Simpang Pulai, and
another extreme-damage incident to other
vehicles in 2023. This has shown how urgent it is
to implement sustainable risk management in
Kinta Valley to protect lives and properties.
Even though several aspects could
influence the rockfall incidents in Kinta Valley,
rainwater was the primary component causing
these events. In Malaysia's tropical climate,
continuous water flow leads to the prolonged
dissolution of limestone, especially along its
discontinuities, which in turn causes the
deterioration of slope stability over time [7]. This
process is a significant factor in the overall
weathering of rock masses in the region [7].
Subsequently, the cohesiveness of rocks at
joints and cracks was further exacerbated by
chemical weathering and quarrying activities.
These aspects also occurred alongside other
factors, including wind-related plant movement,
earthquakes, and vibrations [39]. Another study
also discovered numerous elements substantially
contributing to rockfall incidents in Kinta Valley,
such as seismic activities, water dissolution, and
broad joints with faults [40].

604

Table 1. Significant incidents in Kinta Valley,
Perak, from 2004 to 2023
Location
of
incident

Date of
event

Reported
Damage/
fatalities

Source

Mount
Bercham,
Perak

Dec 12,
2004

Structure
damage, two
deaths, & five
injured

[41],
[42],
[43]

Mountain
Pass, silver
borderPahang

April
2006

[41],
[42]

Gunung
Karang Besar,
Keramat Pulai

June 5,
2008

A mega-sized
failure covered
1/4 of the rock
body on this
mountain.
Vehicle damage
& one death

Yee Lee
Edible Oils
Factory
(Gunung
Lang, Ipoh)

Feb 13,
2012

Structural
damage and no
fatalities

[42],
[43],
[44],
[45]

Gua
Tempurung,
Kampar

April 11,
2012

No reports of
structural
damage or
fatalities

[42],
[43],
[44],
[45]

Quarry at
Keramat Pulai,
Simpang Pulai

July 1,
2019

Vehicle damage
& one death

[7],
[46],
[47]

March 8,
2022

Two deaths &
two injured

[48]

Sept 5,
2023

Vehicle damage
and one injured

[49]

[7],
[42],
[43]

Case Study for Rock Avalanches
A study by [50][51] found that rock
avalanches were remarkable and destructive
natural events. The study described that rock
avalanches were distinguished by their
exceptional speed, enormous size, and the fluidlike movement of fragmented rock. A rock
avalanche typically occurs from significant rock
slides or collapses, in which large masses
(millions of m3) abruptly break away from a
mountainside [50]. The large amount and speed of
the sliding rock turn these masses into a fluid-like
stream resembling a massive waterfall made of
stone [50]. Although the precise mechanisms are
still unknown, rock avalanches often result from
substantial rock slides or falls caused by different
sources. Specific examples that can trigger these
catastrophic events include earthquakes, volcanic
eruptions, heavy rainfall, and human activities [50]
The precise mechanisms driving rock
avalanches remain poorly understood. Numerous
studies have investigated potential causes and
contributing factors. Research by [50] mentions

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that the propagation of a rock avalanche is
influenced by various factors, with shear forces
and internal stress differences playing key roles.
These forces are evident in the sedimentary
deformation structures observed within the
avalanche deposits. Liquefaction is not
considered a primary contributor to the
propagation of rock avalanches. Rather than the
rock mass itself, the nature of the terrain the
avalanche travels over significantly influences its
movement, highlighting the complex and variable
nature of these events [50][51].
Rock avalanches are usually uncommon in
Malaysia. Nevertheless, a rare rock avalanche
incident occurred in 2015 on the rock face of
Mount Kinabalu. This mountainous region is
situated in Sabah, the first United Nations
Educational, Scientific and Cultural Organization
(UNESCO) World Heritage Site in Malaysia [52].
On June 5, 2015, a 6.0 magnitude earthquake
caused rock avalanches on the rocky flanks of
Mount Kinabalu, producing noticeable marks on
the surface [52, 53, 54]. This earthquake was
documented as one of the most powerful natural
phenomena following the 6.2 magnitude Lahad
Datu earthquake on July 26, 1976 [55].
Consequently, a significant boulder avalanche on
the slopes of the mountain caused 18 immediate
fatalities [54][55].
Seven pupils and two teachers from the
Tanjong Katong Primary School (TKPS),
Singapore, and a Singaporean adventure guide
who were reported missing following the
earthquake have been discovered deceased.
Meanwhile, six Malaysians (including four
mountain guides) perished. Two tourists (one
Chinese and one Japanese national) were also
killed [54]. This major incident demonstrated that
the implications of the earthquakes, rock falls, and
debris flow could heighten the exposure and risk
levels due to the mountainous terrain and popular
tourist activities (climbing, camping, and tourism)
[52].
Figure 4 illustrates the earthquake
distribution in Sabah between 1900 and 2019,
obtained from the United States Geological
Survey (USGS) database. During the period,
Sabah experienced 67 light to moderate
earthquakes, most of which were below 5.0 on the
moment magnitude scale (Mw). However, four
significant quakes occurred with magnitudes of
6.0 Mw or higher. These larger earthquakes
include the 2015 Ranau earthquake (6.0 Mw ), the
1976 Lahad Datu earthquake (6.2 Mw ), the 1951
Kudat earthquake (6.1 Mw ), and the 1923 Lahad
Datu earthquake (6.3 Mw ) [55].

Figure 4. The earthquake distribution in Sabah
between 1900 to 2019. This data was extracted
from the USGS database [55]
The majority of this seismic activity was
concentrated in the Ranau and Lahad Datu
regions.
Causes of Rock Slope Failure
Due to the country's rapid infrastructure
development and the inherent geological and
climatic conditions, rock slope failures in Malaysia
are a significant concern. A comprehensive
understanding of the key factors, underlying
causes, consequent impacts, and mitigation
strategies is imperative for effective slope
management and safety.
Table 2 summarizes the causal factors
contributing to rock slope failures in Malaysia. The
table details the effects of weathering, heavy
rainfall, seismic activity, and human actions on
slope stability. For each factor, relevant processes
are outlined, including chemical and differential
weathering, pore pressure augmentation due to
rainfall, seismic shaking through weathered or
fractured rock, and the destabilizing effects of
construction and deforestation. This compilation
provides a concise framework for comprehending
the complex interaction of natural and
anthropogenic factors in rock slope instability.
DISCUSSION
Figure 5 illustrates the critical factors,
causes, consequences, and mitigation strategies
related to rock slope failures, a significant
geological risk in Malaysia. This issue was roughly
comprehended by categorizing it into two
essential aspects: rock movement (failure types:
rock slides, rock falls, and rock avalanches) and
triggering events (factors generating instability).

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Table 2. Causes of rock slope failure.
Cause Factor

Explanation

Ref.

Weathering –
Alteration

Weathering changes rock
properties, forming weak zones
that can lead to slope failure.
In tropical climates, limestone
dissolves under moisture,
reducing its structural strength.
Chemical weathering reduces
the cohesive strength of rock,
increasing the risk of instability.
Varying weathering rates in
sedimentary rocks form weak
planes, triggering slope
instability.

[6]

Intense, frequent rain saturates
slopes and increases pore
pressure, reducing friction and
stability.
Prolonged and high-intensity rain
further infiltrates slopes,
weakening their structure and
promoting landslides.
Seasonal monsoon rains can
trigger landslides, especially in
areas with already-weathered
rock or residual soils.
Rain infiltration raises pore water
pressure, lowering effective
stress and shear strength.
Extended rainfall saturates finegrained soils, significantly raising
the risk of slope failure.

[57],
[58]

Seismic activity can worsen
existing rock weaknesses,
triggering slope failures.
Certain areas in Malaysia, such
as Bukit Tinggi and Ranau, are
more susceptible to seismic
disturbances.
Strong shaking from earthquakes
or heavy loads can cause a
slope to fail, especially in weak
rock.
Events like the 2015 Sabah
Earthquake underscore the
importance of considering
seismic factors in slope stability
assessments.

[56],
[61]

Infrastructure development,
excavation, and poor land use
weaken slopes, triggering
failures.
Deforestation and construction
alter drainage patterns,
increasing slope instability.
Building or operating near slopes
disturbs natural stability, raising
landslide risks.
Slope failures result in significant
economic losses and social
disruption, emphasizing the need
for better land-use practices and
planning.

[56],
[62]

Weathering –
Dissolution
Weathering –
Cohesive
Loss
Weathering –
Differential

Rainfall –
Heavy
Rainfall
Rainfall –
Intensity &
Duration
Rainfall –
Monsoon
Rainfall –
Pore Pressure
Increase
Rainfall –
Soil
Saturation
Seismic –
Activity
Seismic –
Regional Risk
Seismic –
Geology &
Weathering
Seismic –
Historical
Impact

Human –
Activities
Human –
Environmental
Interactions
Human –
Infrastructure
Development
Human –
Economic &
Social Impact

606

[7]
[56]
[7]

[58],
[59]
[56],
[60]
[58],
[59]
[57],
[58]

[7]

[56]

[7]

[56],
[62]
[56],
[62]
[56],
[57]

Figure 5. A flowchart indicating the rock slope
failure aspects involving factors, causes,
consequences, and mitigation strategies.
Each type presents unique challenges based on
the movement and volume of rock involved. These
failures are often influenced by the geological
characteristics of the slope, including the
presence of discontinuities such as joints and
fractures, the type of rock, and the degree of
weathering.
Heavy rainfall has primarily contributed to
slope failures in Malaysia [58, 63, 64]. Rainfall
infiltrating rock formations increases pore
pressure, weakening the rock structure and
making slopes more susceptible to failure.
Additionally, acidic rain accelerates rock
deterioration through chemical weathering, further
compromising slope stability [63]. These factors
underscore the critical role of rainfall in triggering
slope failures in Malaysia, emphasizing the need
for comprehensive risk assessment and mitigation
strategies to address the challenges posed by
changing climatic conditions.
Human actions significantly contributed to
rock slope failures. For example, deforestation
and construction operations disrupted the
equilibrium of slopes, leading to destabilization.
Inappropriate construction on unsuitable terrain
without adequate planning and measures also
increased the likelihood of rock slope failures.
Weather conditions, like freeze-thaw cycles, exert
additional pressure on rock masses, while seismic
events like earthquakes can further destabilize
already fragile slopes. This type of seismic activity

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p-ISSN: 1410-2331 e-ISSN: 2460-1217

can cause subsidence movements, leading to
slope failure as the land gradually sinks, disrupting
the balance and stability of rock slopes. Research
has shown that seismic activities in Malaysia,
notably the earthquake in Ranau in 2015, have
highlighted the vulnerability of slopes to landslides
[54][65]. The seismic considerations in structural
design, as emphasized after the SumatraAndaman earthquake, are crucial to preventing
fatalities and injuries caused by structural failures
during earthquakes [66]. Studies on bridges in
Malaysia have shown varying seismic fragility
curves, indicating different probabilities of damage
levels based on pier heights and ground motion
intensities [67]. Overall, seismic activities can
trigger landslides and affect the structural integrity
of various types of infrastructure in Malaysia,
emphasizing the importance of seismic
considerations in design and construction
practices.
Due
to
Malaysia's
geographical
topography, which features steep hills and
densely populated areas, the frequency of rock
slope failures could increase. The risk of such
failures has also significantly increased,
particularly in Malaysia, due to the expansive
infrastructure development within and around
slopes [62]. There have been various methods in
Malaysia to evaluate and reduce slope instability,
such as rock mass classification systems, slope
mass rating (SMR), including kinematic analysis
[7][68].
Besides,
geophysical
techniques,
including electrical resistivity and remote sensing
tools such as light detection and ranging (LiDAR),
have also been embraced to enhance rock slope
stability investigations in the country [68][69].
Similarly, applying soil bioengineering techniques,
especially on whole plants, has been identified as
an alternative approach for slope stabilization,
particularly in low to moderate-risk category
slopes [62]. The combination of these efforts is
germane to addressing the issues related to
infrastructure development and natural factors
that lead to failures in slope areas within Malaysia.
Rock slope failures in Malaysia can have
severe consequences, as in Table 3, including
human injuries or fatalities, property damage,
economic disruption, and environmental damage.
If these incidents were not mitigated, a chain
reaction of impact could be extended in regions
surrounding the rock slope failures. These
incidents were also costly to resolve.

Table 3. Consequences of Rock Slope Failure
Consequences / Description

Ref.

Loss of Life and Injuries
The 1993 Highland Towers collapse killed 48 people.
Bukit Lanjan failure (2003) endangered a busy area,
while rockfalls at Cheras, damaged property,
requiring mitigation.

[7],
[64]

Property Damage
The Bukit Lanjan incident shut down a major
expressway, highlighting the risk of severe property
damage and traffic disruption.

[7]

Economic Disruption
Slope failures in tourist areas lead to financial losses
from disrupted tourism and damaged attractions.
Repair, mitigation, and maintenance costs add further
economic strain.

[64],
[70]

Environmental Damage
Slope failures accelerate soil erosion, damage
habitats, and disrupt drainage. Sedimentation in
waterways can harm flora and fauna, causing longterm ecological effects.

[71],
[72]

For example, interruptions of transportation
pathways (highways and railways) could produce
decreased productivity, freight delays, and higher
operational expenses. Another example involved
repairing
and
rehabilitating
damaged
infrastructure, which created significant financial
strain on relevant parties. Therefore, long-term
implications could be concerning due to the
negative financial impacts, impeding economic
expansion, and advancement.
Considerable environmental concerns
could be presented from rock slope failure
incidents, in which waterway sedimentation, loss
of habitat, and soil erosion could occur due to
natural landscape modifications. These incidents
can also lead to the contamination of water
sources by releasing dangerous substances,
posing threats to human health and aquatic
ecosystems. Therefore, introducing sustainability
principles in rock slope management strategies is
essential to prioritize preventive actions and
minimize the ecological impact of failures. This
approach allows for identifying methods to
mitigate rock slope failures, as shown in Table 4.
Monitoring and examining failure-prone
areas using extensive tests and advanced
technologies is essential. In high-risk slope areas,
it is necessary to conduct comprehensive tests
and utilize advanced monitoring techniques for
both control and examination.

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SINERGI Vol. 29, No. 3, October 2025: 599-614

Table 4. Rock Slope Failure Mitigation Strategies
Method/ Approach

Key Points

Ref.

Rock Mass
Classification &
Rating
(SMR, Kinematic
Analysis)
Geophysical &
Remote Sensing
(Electrical
Resistivity, LiDAR)

Systematically evaluate
rock-mass quality and
discontinuity orientations
to diagnose failure modes
and prioritize mitigation.
Enhances slope
investigations by imaging
moisture and weak zones;
delivers terrain/structural
data for assessment,
warning, and mitigation.
Stabilizes low, moderate
risk shallow slopes
through root reinforcement
and erosion control,
providing sustainable
mitigation alternatives.
Enables early warning and
risk reduction by
monitoring slope
movements, moisture
changes, and real-time
data.
Implemented after
identifying vulnerable
slopes to reinforce weak
zones, control water flow,
and stabilize failing rock
masses.
Requires strict
geotechnical standards,
effective emergency plans
(rescue, communication,
evacuation), and long-term
recovery efforts like
replanting.

[73],
[74]

Soil
Bioengineering
(Whole Plants)

Monitoring &
Advanced
Technologies
(ERT, Passive
Seismic, DInSAR,
IoT, AI, MEMS)
Mitigation &
Prevention
(Rock Bolting,
Drainage Systems,
Retaining Walls)
Regulations,
Preparedness &
Response

[75],
[76]

[62],
[77],
[78]

[79],
[80],
[81],
[82]

[83],
[84],
[85],
[86]

[16],
[87],
[88]

Effective methods such as Electrical Resistivity
Tomography (ERT) [75][89] can explore
subsurface moisture dynamics, a key driver of
slope failure events. Advanced monitoring
measures like passive seismic monitoring [80] can
detect changes in fundamental resonance
frequencies and slope deformation, offering a
deeper understanding of slope conditions.
Furthermore, contactless methods like
DInSAR [79] can be used cost-effectively and
efficiently to survey large areas for potential
landslide hazards. Integrating technologies such
as the Internet of Things (IoT) and Artificial
Intelligence (AI) for monitoring soil hydrological
conditions and tracking slope movements [81] will
enhance early warning systems and reduce risk.
The use of Micro Electro Mechanical Systems
(MEMS) tilt sensor arrays in monitoring is another
option, providing advances in early warning
against potentially dangerous slope movements
and enabling timely preventive measures, such as
evacuation warnings for high-risk areas [82].

608

Moreover, incorporating the anticipated
probability and timing of future failures should also
be acquired in improved prediction models by
delivering data regarding geological properties,
rainfall, and seismic activity for specific mitigation
initiatives. Subsequently, different mitigation and
preventative techniques (rock bolting, drainage
systems, retaining walls) can be implemented
after vulnerable slopes are located [83].
Strict
regulations
and
geotechnical
expertise should be followed and incorporated into
the infrastructure framework as preventive
measures. Nonetheless, preparedness and
response measures are still crucial if an incident
occurs. A prompt and efficient response involving
search and rescue operations, communication
protocols, and evacuation methods can then be
utilized. The long-term management should also
include sustainability and recovery initiatives, such
as replanting and post-failure recovery plans
containing environmental factors.
Benchmarking our Findings Against Literature
from Recent Studies
Our finding indicates that the performance
of rock slopes is primarily controlled by three
factors: unfavorable rock mass structures, such as
steep, exposed discontinuities, weathering, and
transient forces like rainfall and seismic activity.
This aligns with recent studies from Malaysia that
highlight the same dominant controls and note an
increased risk as urban development expands into
hillside areas [7]. The role of seismic loading is
strongly supported by the 2015 Mw 6.0 Ranau
earthquake. This event generated 5,198 slope
movements across ~810 km², demonstrating that
slopes with pre-existing structural weaknesses are
highly susceptible to rapid failure during seismic
shaking. This corroborates our finding that
adverse geological structures can lead to coseismic failure [54]. Additionally, our findings of
hydroclimatic impacts reported for the same
region further align with our consequence chain,
which is multi-temporal satellite analyses show
immediate channel adjustments after the
earthquake and sustained, five-year geomorphic
responses, underscoring how extreme events
perturb slope river systems and amplify risk
downstream [65]. Finally, our recommendations
for risk assessment, continuous monitoring, and
preparedness are consistent with current best
practices. For example, high-temporal-resolution
terrestrial Structure from Motion (SfM) has been
used to quantify daily rockfall activity, and
automated photo-monitoring systems are now
extracting detailed rockfall inventories for hazard
evaluation. These approaches support our call for

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p-ISSN: 1410-2331 e-ISSN: 2460-1217

implementing near-real-time surveillance systems
for early warning and effective mitigation design
[90][91]. In conclusion, our findings on the causes
of slope failure, which include structural
weaknesses, degradation, and transient forces,
are consistently supported by prior research. This
convergence with existing event inventories and
monitoring studies also extends to the resulting
multi-year
systemic
impacts
and
the
recommended mitigation strategies, such as
instrumented monitoring and preparedness. This
alignment validates our conclusions and
underscores the practical relevance of our
recommendations.
CONCLUSION
This review successfully investigated the
rock slope failure incidents in Malaysia by
presenting the difficulties in areas with varied
geological formations. By categorizing failures into
types such as rock slides, rockfalls, and rock
avalanches, and analyzing the factors affecting
these incidents, including natural events such as
weathering, heavy rainfall, seismic activity, and
human activities, which collectively elevated the
likelihood of rock slope failures (particularly during
intense rainfall). This review also determined
several issues, such as injuries, fatalities, and
property damage. These issues demonstrated
infrastructure disruptions, leading to economic
expenses involving lower productivity, repair
expenses, and transportation delays. Overall,
Malaysia should use comprehensive mitigation
solutions to achieve resilience and sustainability in
dealing with rock slope failures. These solutions
should include early warning systems, slope
stabilizing techniques, and data-informed landuse planning.
ACKNOWLEDGMENT
This review is supported by the University
of Tun Hussein Onn, Malaysia, and the Ministry of
Higher Education, Malaysia, for the Hadiah
Latihan Persekutuan (HLP) scholarship. The
information obtained in this review provides
valuable insights into Malaysian disaster
management's current and future landscape.
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