Lessons Learned from Reina Landslide of the Philippines1
This case study provides the unique example of river basin management problem in
Quezon province in the Philippines, where the debris flow is affecting the river flow,
and increasing the delta region in the river mouth. Lack of proper land use planning and
drainage, the area often has flash flood. The area was hit by a strong typhoon and sever
rainfall in 2004, causing a huge landslide with affected the lives and livelihood of the
people. In the Infanta are of Quezon city, the effect was quite similar to that of
Toyooka case study of Japan. The houses and people were affected by the timbers and
logs transported downstream, and deposited on the flat land. The involvement of the
local governments in the natural resource management and thereby solving the disaster
problems is found to be essential. It has been observed that improper planning is the
root cause in many cases. Proper geo-hazard mapping is not done in the area, and thus,
the case study recommends the coordination between the mapping and the development
practices. 11 lessons were learned from this case study, which are listed below:
Lesson 1: Deltas are built on river debris deposits: The case study area is located along
the Philippines Fault line, which is the weak zone and defines the course of the river
system. Continuous sediment deposit and rain enhance the growth of the delta, and
thereby affecting the debris flow in the region.
Lesson 2: Anomalous drainage pattern: The location is the site has its characteristic
drainage pattern. The topography is such that the drainage area is concentrated over
100 sq km, which is circular in nature. This anomalous drainage pattern also enhanced
the cause of damages. Also, fault controlled river system tend to concentrate the flow
along a narrow river system.
Lesson 3: Vegetation and slope angle: It is argued that thick vegetation controls the
land erosion and helps in preventing landslides. However, it is not only the nature of
1
This case study is a summary of the power point file of the DENR (Department of Environment and
Natural Resources, presented in the NDCC (National Disaster Coordination Council) meeting in the
Office of Civil Defense (OCD).
vegetation, but depends on the slope angle. A gentle slope with less vegetation may not
cause landslide, whereas a steep slope with thick vegetation can cause landslide.
Lesson 4: Rooted trees versus cut logs: Illegal logging is considered as one of root
cause of land erosion in the upstream. But the current landslide and flood showed that
uprooted trees also caused significant damages. Thus, the main issue was basic forest
management.
Lesson 5: Lack of implementation measures at LGU level: Although the DENR
submitted the landslide susceptible maps to the local government unit in March 2004,
the LGS did not pay attention to it. The same areas were flooded by November rainfall.
Lesson 6: Recurring problem: The area is located on an old debris flow deposit. Thus,
there are evidences of several landslide and debris flow in the past.
Lesson 7: Identify other problem areas: The problem is not only confined to landslide
issues. It is related to other different aspects of inter-barangay (local government units)
politics, and is very much related to the local socio-economic and cultural context.
Lesson 8: Disaster Management Education: It is required to enhance the understanding
and awareness of disaster management for the local residents. Many of the houses are
located at the foothills of vulnerable slopes.
Lesson 9: Costly but life-saving measures: It is required to protect cut slopes, although
it may see costly. It has a high value of life saving.
Lesson 10: Coordination: Multi-stakeholder coordination is an essential factor. It is
required to develop coordination among the local authorities, infrastructure builder/
developer and geo-hazard mapping agencies.
Lesson 11: Geo-hazard maps: Geo-hazards maps are useful for both post-disaster
damage assessment as well as pre-disaster planning. DENR is conducting geo-hazard
mapping of priority areas, which are vulnerable to natural hazards.
Thus, in summary, the case study has a series of social lessons, institutional lessons,
policy lessons and technical lessons. Environment and disaster issues are inter-linked,
as evidenced from the current case study.
Vegetation cover
versus land slope
People living at
the foothill of the
vulnerable slopes
Satellite image
before and after
the landslide