View Presentation - University of the Philippines Diliman

Case Studies of Slope
Failures in the Philippines:
A 10 Year Retrospective
Mark Albert H. Zarco
Sandra G. Catane
University of the Philippines
Diliman, Quezon City
THE PHILIPPINES: A HAZARD
PRONE COUNTRY
• The geographic and geologic setting of the Philippines
make it naturally prone to various hazards including:
– Hydrometeorological induced;
– Earthquake induced;
– Volcano related;
• These conditions either individually or in combination
with each other or together with anthropogenic factros
make the Philippines particularly vulnerable to
landslides.
• This presentation summarizes the major landslides in the
Philippines that have occurred in the last 10 years.
CHERRY HILLS SUBDIVISION, ANTIPOLO, RIZAL
(Photo: PHIVOLCS)
Photo:
• August 3, 1999 after 3 days of
continuous rains and 500 mm of
rainfall;
•59 killed, 39 injured, 379 houses
destroyed;
• Attributed to over steepening of
slope during constructions;
• Compound failure mechanism
in soft rock involving rational and
translational components
(Pictures and Data care of EMC2
and Partners)
MUNICIPAL SOLID WASTE SLIDE
JULY 2000, PAYATAS, QUEZON CITY
• July
9, 2000
•16000 cu.-m
• 32.5 m height
• 278 killed, 650 missing,
68 rescued
• 1-day rainfall of 170mm
Pictures and data from Merry
and Kavazanjian, 2004.
RAINFALL DATA, PAYATAS, QUEZON
CITY 2000
160
Daily Rainfall (x 10-3 m)
1800
Daily Rainfall
Total Rainfall
140
1600
1400
Failure
120
1200
100
1000
80
800
60
600
40
400
20
200
0
0
05
/ 01
05
/0 0
/1 5
05
/ 00
/2 9
06
/ 00
/ 12
06
/0 0
/2 6
07
/0 0
/ 10
07
/0 0
/ 24
/0 0
Data from PAGASA
Total Rainfall (x 10 -3 m)
180
Miag-ao Landslide
Profile of UP Miag-ao Landslide
A
A'
100
Globe Tower
Landslide
Slope Cut
Admin. Bldg.
Road
50
Creek
0m
0
100 m
UPV Miag-ao Landslide
Source:
UPViews,
August
2006
Miag-ao Landslide
Panaon Island
December 2003
Panaon Island
(December 2003)
Panaon Island Debris Flow 2003 (Photo: MGB)
• 200 killed
• 200 mm rainfall in
1/day; 700 mm in 3-days
Panaon Island Landslide 2003 (Photo: MGB)
120o E
118o E
122o E
124o E
126o E
N
18o N
0
20 0
LUZON
Lingayen
Gulf
PHILIPPINE
SEA
o
16 N
10 0
SOUTH
CHINA
SEA
Manila
Bay
14o N
Mindoro
Strait
o
12 N
VISAYAS
Palawan
10o N
SULU
SEA
8o N
6o N
MINDANAO
Debris Flow and Flooding, Quezon
Province
December 2004
General Nakar, Quezon, 2004
Photo: Barreto, 2007
Damaged part
General Nakar
General Nakar
Infanta
Accumulated
debris
Infanta
2004 Infanta, Quezon Mudflows
Photo: MGB
The
The landslides
landslides that
that hit
hit Quezon
Quezon Province
Province is
is another
another example
example of
of rotational
rotational landslide.
landslide. (MGB
(MGB
2004)
2004)
Brgy.
Brgy. Mayana,
Mayana, Jagna,
Jagna, Bohol
Bohol Province
Province
July
July 2005
2005
Photo Source: MGB 2005
GUINSAUGON LANDSLIDE
Source Area: Epiclastic Rocks
Guinsaugon
Avalanche Area
Debris Flow Area
Himbungao River
Apex of the
landslide scar
Stream
Translated 3-storey
concrete building
GUINSAUGON
VILLAGE
Damming of streams
Rock Impact Marks
Cobbles and boulders
at fringes of avalanche
Flooding
AVALANCHE
From: R. Solidum, 2007
From: R. Solidum, 2007
From: R. Solidum, 2007
PHILIPPINE RECLAIM PROJECT
(Baguio City)
LANDSLIDES
Landslides in Maasin, Iloilo
Landslides in the upland
villages of Janiuay, Iloilo
MGB-DENR, Region VI
Landslides at the headwaters of Aklan
River
MGB-DENR,
Region VI
Pavia, Iloilo
Kalibo, Aklan
Summary
• Landslides in the Philippines are varied in
nature:
– Involving different types of material: Soft rock
and karst, highly plastic materials, Lahar, and
MSW;
– Involving different mechanism: shallow to
deep seated;
– Involving widely varying time scales from slow
creeping slides to very fast rockslide and
debris avalanches;
– Approach must be site specific
Summary
• Rainfall Seems to be the most common
factor
– Cherry Hills : 500 mm/1 day
– Payatas : 380 mm/ 3 day
– Panaon: 700 mm/ 3 days
– Quezon: 342/ 6 hours
– Guinsaugon: 760/ 15 days*
– Albay: 500 mm/1 day
– Panay: 250-320/ 1 day period
Summary
• Involves multiple hazards
– Guinsaugon: rainfall induced/earthquake triggered;
– Mayon: Volcanic Eruption resulting in debris flow;
– Panay: Landslide resulting in flooding
• Landslides pose a major threat to life, limb and
property
– More than 4000 lives lost in 10 years;
– P 15B to P 20B in lost property, infrastructure and
livelihood;