region xii geohazards
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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).
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