SPOT REPORT ON THE LANDSLIDE INCIDENT IN
BRGY. MARAYAG, LUPON, DAVAO ORIENTAL
In the first week of January 2014, a Low Pressure Area (LPA) brought torrential rains for several days
in different parts of the region particularly in the provinces of Davao del Norte, Compostela Valley and
Davao Oriental causing widespread flooding and several landslides. Based on the Situation Update of
the Office of Civil Defense XI dated January 14, 2014, 13 were reported as casualties while 7 are still
missing from different areas in the region. Among the fatalities/missing, 3 are from Brgy. Marayag,
Lupon, Davao Oriental.
Brgy. Marayag with geographic coordinates of 126°9'41.789" east longitude and 7°9'21.292" north
latitude is located about 33 kilometers (linear distance) northeast from Lupon proper and can be
reached via the unpaved Mati-Maragusan road. The assessed site is characterized by flat to
undulating terrain flanked by steep slopes and mountainous terrain which is underlain by poorly
indurated and highly weathered diorite to the east and metamorphosed sedimentary rocks to the west
(ABS & CAA, July 1982) while the flat central portion is underlain by Recent alluvial deposits. The
eastern side is part of the Katian Mountain Range with the highest elevation of 1640 masl and to the
west is part of the Tagopo Mountains with its peak at 920 meters.
The area is mainly drained by Sumlog River and its several tributaries characterized by
angular/rectangular drainage system cutting through steeply incised valleys. This type of drainage
pattern is a result of the structural control joints or faults in the bedrock. Sumlog river generally trends
in a NNW-SSE direction in the upper reaches or headwaters and shifts to a NE-SW direction from
Barangay Don Mariano Marcos as it exits towards Lupon and eventually drop is loads to Cuabo Bay.
Based on previous reports (NBA and RTV, Sept 2006), the assessed site as well as the adjacent
Brgy. Calapagan is believed to be a pull-apart basin developed due to the movement of the left-lateral
strike slip fault within the Philippine Fault Zone. The main fault identified as Bitanagan Fault (ABS &
CAA, July 1982) generally trends NNW and passes along the break-in-slope defining the gently
undulating terrain and the mountainous area.
As per interview, the landslide which is a characteristic of a debris flow type of mass wasting occurred
on January 12, 2014 at around 4:00 am. Although several debris flows were noted along the road on
the way to Marayag, the area that was severely affected is Po. Madasigon (proper) of Brgy. Marayag
damaging several infrastructure and houses including the barangay hall and covered court. During the
assessment, it was noted that the debris flow shifted westward towards the barangay hall and houses
as the original channel was already filled up by debris deposit. An estimate of 1 to 2-meters thick of
debris deposit composed of sand to cobble to boulder-size rocks and uprooted trees and logs covered
the area. Most of the gullies in the purok and in the vicinities served as the channel way of the debris
flow.
According to the locals, the occurrence of this type of natural hazard in the area is common. They
added that similar debris flow but in a smaller scale happened in 1976 (?), 1986 (?) and in 1993 (?).
Based on the information given, a 10-year flood/debris flow affects the site or its vicinities. Previous
reports available in MGB-XI also noted the debris flow that affected Brgy. Calapagan in 2006.
Moreover, results of the 1:50,000 scale geohazard mapping, Brgys. Marayag and Calapagan were
Republic of the Philippines
Department of Environment and Natural Resources
MINES AND GEOSCIENCES BUREAU
Regional Office No. XI 669 Konsuela Bldg., Aurora Quezon Street, Davao City Tel. No. (082) 222-5601 Telefax No. (082) 221-6535 Email: [email protected]
identified as very highly susceptible to landslide taking into account its location within the Philippine
Fault Zone.
During the undertaking, two possible temporary relocation sites were identified by the undersigned.
These are located in Po. DTM (Brgy Site) and Po. Marasigon (Ridulla property), all in Brgy. Marayag
and approximately centered in geographic coordinates 126°9'39.8" east longitude/7°9'50.377" north
latitude and 126°9'53.291" east longitude/7°9'26.713" north latitude, respectively. Po. DTM relocation
site is approximately 1km north from the barangay hall. It is situated on a relatively elevated area
bounded by gullies to the east and west. The second relocation site is located in Po. Madasigon about
400 meters NE from the barangay hall. The site is also elevated and bounded by a perennial creek to
the east. It is characterized by flat to nearly flat topography and grades to moderately steep towards
the north. However, taking into account the geologic setting of the area, earthquake-related geologic
hazards, slope failures and flooding may likely affect the area in the future.
BEVERLY MAE M. BREBANTE Supervising Science Research Specialist
“MINING SHALL BE PRO-PEOPLE AND PRO-ENVIRONMENT IN SUSTAINING WEALTH CREATION
AND IMPROVED QUALITY OF LIFE”
PHOTOS