Department of Environment and Natural Resources

MINES AND GEOSCIENCES BUREAUGeological Sciences Division

Region XIIKoronadal City

Tel. No. (083) 228 61 30 & 31

GEOHAZARDS IN REGION XII

JAIME G. FLORES, MS ERM

Chief Geologist

Mines and Geosciences Bureau

Region XII

PROVINCETOTAL

MUN/CITYTOTAL BRGYS

AREA, sq. km

SOUTH COT 11 199 3,689.69

NORTH COT 19 591 14,227.85

SULTAN KUD 12 248 4,755.89

SARANGANI 8 166 4,636.48

TOTAL 50 1,204 27,309.91

ADMINISTRATIVE MAP

ACCESSIBILITYROAD NETWORK

SLOPE MAP

PHYSIOGRAPHIC MAP OF REGION XII

Four Major Landforms of Region XII

1. The Cotabato Basin at the center (Marshland) have less rainfall compared to the others due to elevation

2. The Lanao-Bukidnon Highland on the north

3. Daguma Mountain Range

4. Central Cordillera on the east

5. . Sarangani Peninsula on the southeast

DRAINAGE SYSTEM and WATERSHED AREAS

Code Watershed Run Off

Volume, m3

River

Discharge

,

m3/sec

Jurisdiction

W1 Allah River 8.3 x 108 47.41 AVLDA

W2 Banga River 2.7 x 108 8.45

W3 Kalaong River 2.6 x 108 8.20 Maitum

W4 Seguil River 2.2 x 108 7.00 Gensan/Maasim

W5 Marbel River 2.1 x 108 6.74 Kor City, Tupi,

Tampkan

W6 Silway-Clinan

River

1.9 x 108 6.16 Polomolok, T’boli,

Gensan

W7 Buayan-Maribulan

River

1.3 x 107 Gensan & Alabel

W8 Lun Grande River 5.2 x 106 Alabel &

Malapatan

W9 Maitum-Kiamba

River

3.9 x 106 Maitum & Kiamba

W10 Maasim River 3.5 x 106 Maasim

W11 Big Glan River 3.4 x 106 Glan

W12 Margus Grande

River

2.2 x 106 Glan

W13 Malapatan River 1.9 x 106 Malapatan

W14 Makar River 1.3 x 106 Gensan

W15 Sinawal River Gensan

W16 Ticulab River 1.2 x 106 Maitum

W17 MalitubogMaridag

o River

North Cotabato

W18 Kabacan River North Cotabato

W19 Pulangi River Central Mindanao

Watershed is defined as A NATURAL SYSTEM THAT CAN BELOCATED ON THE GROUND BY TRACING THE RIDGELINETHAT SEPARATES THE FLOW OF WATER AND DRAINS TO ACOMMON OUTLET

GEOLOGIC MAP

Mt. Parker

Mt Ragang

Mt Matutum

Mt. Apo

CLIMATE

Rainfall Classification

ITCZ

RAINFALL –RUNOFF PATTERN(SOUTH COTABATO BASIN)

Mean Annual Rainfall (mm) Mean Annual Runoff (mm)

RAINFALL –RUNOFF CHARACTERISTICS

Rain is produced when warm and moist air strikes mountain

ranges (orographic effect) causing to rise to the atmosphere at

condensation point to form droplets of water falls free under pull of

gravity to the earth while the sizes of rain drops increase by

coalescence.

It is noted that rainfall intensity is high at Daguma Range and low

at the surrounding areas of Liguasan Marsh.

Rainfall has its depth measure either in inch or mm duration in 1

hour or 1 day, distribution with respect to geographic position in

earth and pattern reflected in dry and wet seasons.

Runoff is water that flow rapidly from the hill and mountain slopes down to the stream during rainfall.

It is directly influenced by rainfall pattern

Runoff depth refers to water flowing represented in inch or millimeter.

The Allah Valley Landscape

AVL is delineated based on the watershedprinciple stating that any total land areacontributes to the flow of a particular waterbody(river, creek, or stream) and drains to a commonoutlet.

AVL is a natural system and its boundary can belocated on the ground by connecting all thehighest elevations near and around the saidwaterbody thereby tracing the ridgeline thatseparates the flow of water from one river toanother.

Its landscape boundary line is traced betweenpeaks connecting ridges of Daguma and Roxas-Matulas ranges

The landscape with common outlet at Sapakanforms NW trending area enclosing Allah andBanga rivers that joins at Kapingkong beforereaching Liguasan Marsh.

Hazard maps and responsible agencies

Agencies Hazards

MGB, PAGASA Flood

MGB Rain-induced landslide

PAGASA Storm surge

PHILVOLCS Earthquake-related: ground

rupture, ground shaking,

liquefaction, earthquake-

induced landslide, tsunami

PHILVOLCS Volcanic hazards: ashfall,

lava flow, pyroclastic flow,

lahar

FLOOD DEFINED

Flooding is defined by PAGASA as abnormal rise

in the water level of stream that may result in

overflowing by the water of the normal confines

of the stream with subsequent inundation of

area, which are not normally submerged.

Rainfall Intense ranging 45 to 100 mm/hr in 2 to 3 hours

Slope Flat lying area having 0-3% gradient – floodplain

terrain

Drainage System

& Watershed

Area of watershed and capacity of channel ways to

contain its runoff peak discharge

Soil/Rock Types Rocky/Clayey/ soil – Low infiltration, high runoff

Land Use Cover Barren and poor vegetation/Kaingin – Low

infiltration, high runoff

Major Contributing Factors to High Incidence of Flooding

REGION XII FLOOD SUSCEPTIBILITY MAP

SOUTH COTABATO PROVINCE

FLOOD RATINGS

MUN/CITIES TOT BRGYS HIGH MODERATE LOW WATER BODIES

Koronadal City 27 11 10 6 Buloc Crk and Marbel rivers

Gen Santos 26 7 4 15 Silway, Makar, and Buayan rivers

Banga 22 13 8 1 Banga River

Lake Sebu 19 2 17 Alah-Gao River

Norala 14 8 5 1 Banga River

Polomolok 23 3 1 19 Polomolok Crk

Sto Nino 10 2 8 Banga River

Surallah 17 9 6 2 Alah-Sapali River

Tampakan 14 3 3 8 Taplan River

Tantangan 13 7 6 Buluan Lake & Sarcon Crk

T'boli 25 1 3 20 Alah River

Tupi 14 3 12 Palian River

TOTAL 224 69 54 101

NORTH COTABATO PROVINCE

FLOOD RATINGS

MUN/CITIES TOT BRGYS HIGH MODERATE LOW WATER BODIES

Alamada 17 6 3 8 Libungan River System

Aleosan 19 4 1 14 Libungan Marsh

Antipas 13 13

Arakan 28 28

Banisilan 20 20

Carmen 28 11 17 Pulangi-Kabacan River

Kabacan 24 17 3 4 Kabacan River & Liguasan Marsh

Kidapawan City 40 40

Libungan 20 14 6 Libungan River System

Magpet 32 31

Makilala 38 3 38 Malasila River

Matalam 34 6 4 23 Malasila River

Midsayap 57 18 18 20 Liguasan Marsh

Mlang 37 14 7 16 Liguasan Marsh

Pigkawayan 40 13 10 17

Kimarayag River & Libungan

Marsh

Pres. Roxas 25 1 1 28 Kabacan River System

Pikit 42 31 5 6 Rio Grande River

Tulunan 29 7 2 20 Liguasan Marsh

Cotabato City 37 37 Tamontaka & Rio Grande rivers

TOTAL 580 179 57 349

SULTAN KUDARAT PROVINCE

MUN/CITIES TOT BRGYS

FLOOD RATINGS

WATER BODIESHIGH MODERATE LOW

Bagumbayan 19 8 11 Alah River

Columbio 16 3 2 11 Alip River

Esperanza 19 4 12 3 Alah River

Isulan 17 7 7 3 Alah River

Kalamansig 15 1 5 9 Limulan River

Lambayong 26 16 11 Alah River

Lebak 27 9 8 10 Salaman & Tran rivers

Lutayan 11 9 2 Buluan Lake

Palimbang 39 10 13 17 Kraan River

Pres. Quirino 19 19 Buluan Lake

Sen. Ninoy Aquino 20 6 14 Kulaman River

Tacurong City 20 20 Alah River

TOTAL 248 73 99 78

SARANGANI PROVINCE

MUN/CITIES TOT BRGYS

FLOOD RATINGS

WATER BODIES

HIGH MODERATE LOW

Alabel 12 4 2 6 Molo-Ladol Creek

Glan 31 3 23 Glan River

Kiamba 18 5 9

Tual, Badtasan, Tambilil

rivers

Maasim 16 1 14 Maligang & Cablacan rivers

Malapatan 12 1 6

Big Lun, Little Lun, Tuyan &

Malaptan rivers

Maitum 19 6 9

Saug, Kalaong & Pangi

rivers

Malungon 31 31

Buayan, Mateo, Mainit &

Malungon rivers

TOTAL 139 20 98

Most destructive earthquakes Source: OCD, PHIVOLCS, SEASEE

Date Mag Location Dead Injured Missi

ng

Total

Casualty

Remarks

June 3, 1863 Manila 876+ 387+ 1263+ Building collapse

Tsunami

Aug 15,

1918

8.3 SouthCot 100 Houses destroyed tsunami

Apri 1,1955 7.5 Lanao 291 713 1,004 Houses Damaged

Feb 2, 1968 7.3 Casiguran 270 600 870 Building Damaged

Aug 17,

1976

7.9 Moro Gulf 3,792 9,240 1,937 14,969 Building Damaged

July 16,

1990

7.8 Central

Luzon

1,283 2,786 321 4,390 Buillding Damaged,

Landslide, Liquefaction,

Ground Rupture

Nov. 15,

1994

7.1 Oriental

Mindoro

83 430 8 521 Building damage

Tsunami, Liquefaction,

Ground rupture

Liquefaction• transformation of buried sediments to a liquid-like paste by intense ground-

shaking, causing lateral ground spreading, subsidence and sandboils

Tilting/Settlement Lateral Spreading Ground Oscillation

Buoyant rise of buried structures Tilting/Settlement

Characteristics of liquefaction prone areas

Localities prone to liquefaction are:

• a)water-saturated (shallow water table), low-lying

• b) Have loose (unconsolidated), sandy or siltydeposits

• river banks, abandoned rivers, flood plains

• Coastlines

• swamps

Liquefaction Susceptibility Map (PHIVOLCS)

Areas Highly Vulnerable to Ground Shaking and Tsunami due to the presence of Cotabato Trench

1. Cotabato City2. Lebak, Sultan Kudarat3. Kalamansig, Sultan Kudarat4. Palimbang, Sultan Kudarat5. Kiamba, Sarangani6. Maitum, Sarangani7. Maasim, Sarangani

Tsunami

Giant sea waves due to large-scale displacement of the sea floorOverview of

TSUNAMI/STORM SURGE

RATINGS

MUN/CITIES TOT BRGYS HIGH MODERATE LOW

Bagumbayan 19

Columbio 16

Esperanza 19

Isulan 17

Kalamansig 15 11

Lambayong 26

Lebak 27 15

Lutayan 11

Palimbang 39 22

Pres. Quirino 19

Sen. Ninoy Aquino 20

Tacurong City 20

TOTAL 248 48

TSUNAMI/STORM SURGE

RATINGS

MUN/CITIES TOT BRGYS HIGH MODERATE LOW

Alabel 12

Glan 31

Kiamba 18 10

Maasim 16 11

Malapatan 12

Maitum 19 6

Malungon 31

TOTAL 139 27

CONCLUSION

Geologic hazards such as EARTHQUAKE, VOLCANIC ERUPTION, TSUNAMI, LANDSLIDE AND FLOODING are geological or natural processes in the formation of the earth.

They become HAZARDS when lives, properties, infrastructures, growth of economies are at RISK.

The RISK is HIGH when the location & time of human activities, properties and growth of economies are incompatible with presence of HAZARDS.

CONCLUSIONS

• Natural hazards such as flooding and landslide recur in a given place, condition and pattern with magnitude.

• It can be determined, calculated, mapped in terms of vulnerability and forecasted in terms of probability.

• The forces of natural hazards are strong and potentially fatal to lives of the people, damaging to properties, structures, and economy if located in a highly vulnerable areas.

• The impact of hazards is rapid and the chances of saving life of the people, the cost of properties, structures and economy is through effective preparation and quick response.

CONCLUSIONS

• Barangays with o-3% and located near bank of major river channels are highly vulnerable to flooding

• Barangays with slope greater than 18% slope are highly vulnerable to landslide according to Bennet and Doyle (1997), control and limitation, abatement and adjustment are the three principal approaches in dealing with flood hazards

• The choice of management options for mass movement hazards includes: 1) do nothing and accept the loss; 2) remove the problem; 3) avoid the site; and 4) mitigation works and careful building design (Bennet & Doyle, 1997).