Landslides and Flooding

2017/11/17

Welcome Delegates to the 53rd CCOP Annual Session!!! October 16 – 19, 2017

“The Role of Geosciences in Safeguarding Our Environment”

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Cebu City

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Geohazard Information: An Indispensable Tool for Land Use Planning and Disaster Risk Resiliency Implementation

RD LEO VAN V. JUGUAN Mines and Geosciences Bureau 6 53rd CCOP Annual Session October 2017

Philippine Setting Prone to GEOHAZARDS

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Porphyry Cu belts Philippines

Porphyry Cu belts

• Within the Ring of Fire

• Within the Earthquake Belt

• Within the Pacific belt of tropical cyclone (average of 20 TYPHOONS A YEAR)

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Tectonic Map of the Philippines

Source: PHIVOLCS

Negros Oriental Earthquake

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1:50,000 SCALE GEOHAZARD MAPPING AND ASSESSMENT (2005-2010)

The National Geohazard Assessment and Geohazard Mapping Program of the DENR Mines and Geosciences Bureau mandated the conduct of a geohazard mapping for the country as included in the Medium Term Philippine Development Plan of 2004-2010.

HIGHHIGH LANDSLIDEFLOOD SUSCEPTIBILITY SUSCEPTIBILITYAreas likely to experience flood heights Unstableof 1.0 to areas,2.0 meters highly and/or susceptible flood to duration mass movementof more than. 3 days. These areas are immediately flooded during heavy rains of several hours.

MODERATE LANDSLIDE SUSCEPTIBILITYMODERATE FLOOD SUSCEPTIBILITY StableAreas likelyareas to with experience occasional flood or localizedheights of to mass0.5 to movement. 1.0 meters and/or flood duration of 1 to 3 days.

LOWLOW FLOODLANDSLIDE SUSCEPTIBILITY SUSCEPTIBILITYAreas likely to experience flood heights of <0.5 meter and/or flood duration of less Stable areas with no identified than 1 day. These areas include low hills landslideand gentle scars,slopes. either They also active have or sparse relict . to moderate drainage density.

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1:50,000 TIGBAUAN QUADRANGLE (ILOILO & ANTIQUE Province)

1:50,000 LANDSLIDE SUSCEPTIBILITY RATING

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STATUS AND UPDATES ON THE GEOHAZARD MAPPING AND ASSESSMENT IN REGION 6

1:50,000 scale (CY 2005-2010)

Assessment Geohazard Landslide and Assessment Results Maps Flood Threat Report and Available at Available at Advisory Maps MGB 6 MGB 6 Issued to Distributed LGUs to LGUs Aklan Antique Capiz Guimaras Iloilo Negros Occidental

1:10,000 SCALE GEOHAZARD MAPPING AND ASSESSMENT (2011-2014)

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VERY HIGH FLOODLANDSLIDE SUSCEPTIBILITY AreasUnstable likely areas, to experience significant flood areas of heightswhich are in excessaffected of by 2.0 mass meters and/ormovement. flood Humanduration initiated of more effects than 3 days;are usually also prone high. to flashfloods.

HIGH FLOODLANDSLIDE SUSCEPTIBILITY Areas likely to experience flood heights ofSUSCEPTIBILITY 1.0 to 2.0 meters and/or flood duration ofUnstable more than areas, 3 days. highly These susceptible areas are to immediatelymass movement. flooded during heavy rains of several hours.

MODERATE FLOODLANDSLIDE SUSCEPTIBILITY AreasStable likely areas to withexperience occasional flood orheights oflocalized 0.5 to 1.0 to metersmass movement. and/or flood duration of 1 to 3 days.

LOW LANDSLIDEFLOOD SUSCEPTIBILITY Areas likely to experience flood SUSCEPTIBILITYheights of <0.5 meter and/or flood Stableduration areas of less with than no 1identified day. These landslideareas include scars, low either hills activeand gentle or relict . slopes. They also have sparse to moderate drainage density.

1:10,000 MUNICIPALITY OF LEON, ILOILO

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1:10,000 LANDSLIDE SUSCEPTIBILITY RATING

STATUS AND UPDATES ON THE GEOHAZARD MAPPING AND ASSESSMENT IN REGION 6

1:10,000 scale (CY 2011-2014)

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DIFFERENCE BETWEEN 1:50,000 and 1:10,000 Scale

1:50 ,000 scale 1:10,000 scale

• Data collected is on Landslide •Data collected is on Landslide and and Flood susceptibility in the Flood susceptibility of puroks/ barangay proper sitios

• Assesses other important structures in the barangays, such as schools, churches, roads and possible evacuation and relocation sites.

OBSERVATIONS AND FINDINGS

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RESULTS OF THE GEOHAZARD MAPPING AND ASSESSMENT (1:10,000 SCALE)

• Based on the 2011 mapping and assessment in San Joaquin, Miag-ao, Igbaras and Tubungan, all in the Province of Iloilo, LANDSLIDES and FLOODING have a significant impact on agriculture, infrastructure projects and school structures.

IMPACTS OF LANDLSIDES AND FLOOD

AGRICULTURE productive farmlands Less productive More work intensive Unusable

INFRASTRUCTURE PROJECTS High Maintenance Cost Unsafe Unusable Abandoned

SCHOOL STRUCTURES Unsafe school buildings Unsafe evacuation sites

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Day Care Center and Ricefields, Brgy. Buenavista, Tubungan, Iloilo (2011)

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Head

Base

Approximately 10.5 hectares of farmlands were affected/ destroyed by the a landslide in Brgy. Buenavista, Tubungan, Iloilo. (2011)

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A hectare, more or less, of farmland affected by a landslide in Brgy. Signe, Igbaras, Iloilo. (2011)

Affected area

Ricefields affected by flooding, bank scouring and erosion, Brgy. Frantilla and Wayang, Miag-ao.

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Rice Peanuts 2.6 (MT/ha) 1624 kg I. Production Yield per PhP 44,200.00 PhP 41,786.00 hectare Gross Income (Selling price at PhP 17/kg) (Farmgate price at PhP 25.73/kg) (USD 884.00) (USD 835.00)

II. Total Production Cost PhP 13,670.00 - Labor Cost PhP 13,415.00 - Material Inputs PhP 1,820.00 - Drying/Handling/Hauling PhP 28,905.00 PhP 22,981.00 Total (USD 578.00) (USD 451.00) PhP 15,295.00/ha PhP 18,805.00/ha III. Gross Margin (USD 306.00) (USD 376.00)

• Estimated amount of losses to landslides and/or flooding per hectare every cropping period in case farmlands will be affected by landslides and/or flooding (2011)

INFRASTRUCTURE PROJECTS

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BACOLOD NATIONAL HIGH SCHOOL, MIAG-AO, MAY 2011

BACOLOD NATIONAL HIGH SCHOOL, MIAG-AO, AUGUST 2011

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Project Estimated Cost (PhP)

A. Cost of repairs for damaged school building 20,000 to 200,000 (USD 400 to 4,000)

B. Cost of one typical concrete classroom more or less 500,000 (USD 10,000)

• Repairs of damaged classrooms and replacement of destroyed school buildings can be very costly

Road Road Unsafe and hard to maintain road in Brgy. Dalije, Miag-ao.

Road

Unsafe and abandoned 4-kilometer road project, Brgy. Bulho and Cumarascas, San Joaquin, Iloilo. Cost of the road project: PhP10 million(CY 2011.)

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Re-activated Landslides!!!

May and August 2017 landslide in Igbaras, Iloilo

Collapsed portion along Igbaras-Tubungan National Road at Barangays Buga and Riroan, Igbaras Iloilo as a result of a landslide on May 1-2, 2017.

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The MGB 6 assessed the landslide in Igbaras-Tubungan National Road along Barangays Buga and Riroan, Igbaras Iloilo on May 3, 2017 in response to the report and request of LGU-Igbaras to assess the area. In the MGB geohazard assessment and mapping (1:10,000), the two barangays have generally low to moderate landslide susceptibility rating while with some portions have high to very high landslide susceptibility ratings.

August 4, 2017 - The landslide reactivate in the same area.

Landslide that has reactivated last August 04, 2017 and situated along Igbaras-Tubungan National Road, Both the road and its retaining walls were subjected to mass movement.

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According to the DPWH, the damage caused by the landslide to the road construction project amounted to P25,000,000.00 (USD 50,000)

Location map of the subject area within Barangay Buga, Municipality of Igbaras. (Source: Igbaras, Western Visayas, Philippines. 10°44’32.70” N and 122°16’22.90” E. Google Earth)

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Location map of the subject area within Barangay Buga, Municipality of Igbaras. (Source: Igbaras, Western Visayas, Philippines. 10°44’32.70” N and 122°16’22.90” E.)

Infrastructure Projects Estimated Cost (PhP)

10 million A. 4-5 kms. of unpaved farm to market road (USD 200,00)

500,000 to 1 million B. Gabions (20 meters long, 1 meter wide) (USD 10,000 to 20,000)

C. Labor and machine rentals for road at least 10,000/day maintenance (USD 200)

100,000 to 500,000 D. Barangay Hall/Plaza/Basketball Court/Chapel (USD 200 to 10,000)

P25 million E. National Road (USD 500,000)

• Estimated losses for each infrastructures project damaged/destroyed due to landslides

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San Project Miagao Igbaras Tubungan Total Joaquin A. Total No. of barangays 45 79 46 48 218 assessed B. No. of barangays with agricultural areas that are 188 31 68 44 45 highly prone and/or affected by (86.24%) landlslides and flooding C. No. of barangays with infrastructure projects that are 26 39 33 37 135 (62%) highly prone and/or affected by landslides and flooding B. No. of barangays with day care centers, elementary and high schools that are highly 16 16 16 17 65 (29%) prone and/or affected by landlslides and flooding

• The unaccounted impacts of landslides and flooding to agricultural areas, infrastructure projects, education and disaster management to the four landslide-prone municipalities is EXTENSIVE AND VERY COSTLY.

• It may worsen in the coming years if the proper and necessary mitigating and adaptation measures are not formulated and implemented.

THE RELEVANCE OF GEOHAZARD ASSESSMENT AND MAPPING

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THE BARANGAY CAMANDAG, LEON, ILOILO EXPERIENCE June 2008

 In 2006, MGB 6 conducted a geohazard assessment of (7) critical barangays in Leon, Iloilo.  Landslide Threat Advisories issued  Lectures were conducted to the residents of these barangays on landslide and flooding susceptibility of the areas  Preparedness and mitigation measures were emphasized

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 In June 2008, Typhoon Frank hit Iloilo  Brgy. Camandag was severely affected by landslides  32 houses out of 49 were totally damaged and buried.

 Total population is 323.

Brgy. Camandag

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THE GOOD NEWS!!!

 THERE WERE NO CASUALTIES IN BRGY. CAMANDAG . .. DESPITE DAMAGES TO PROPERTIES.

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THE BARANGAY CAWILIHAN, LEON, ILOILO EXPERIENCE August 2011

COMMUNITY APPRECIATION AND APPLICATION OF THE GEOHAZARD MAPPING AND ASSESSMENT RESULTS: THE BRGY. CAWILIHAN, LEON EXPERIENCE

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BRGY. CAWILIHAN, LEON, ILOILO

 About 10.5 kilometers (aerial distance) NW of Leon town proper;  With 56 households;  Located in a ridge, surrounded by steep slopes;  Underlain by highly weathered beds of sandstone, siltstone and mudstone and alluvium;

BRGY. CAWILIHAN, LEON, ILOILO

 Classified as highly susceptible to landslides during the 2008 geohazard assessment;

 The results were discussed with the Punong Barangay and a landslide threat advisory with corresponding recommendations was issued;

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 The advisory was posted in the bulletin board at the barangay hall for reference and information of the residents;

LANDSLIDE THREAT ADVISORY

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 At about past 10:00 A.M. on August 25, 2011 ground shaking was felt in the area;

 According to PHIVOLCS, an earthquake occurred with a 4.5. magnitude and San Jose De Buenavista, Antique as epicenter;

 On August 27, 2011, a landslide occured at Brgy. Cawilihan, Leon at 10:30 p.m. due to strong and continuous monsoon rains brought about by Typhoon Mina.

 Head of the landslide - Barangay proper;  Base of the landslide - Sibalom River;  The affected area is about 20 hectares;  Eight (8) houses occupied by 11 families were totally damaged; • Rendered 20 hectares of farmland unfit for rice production.  Portions of the barangay road, more or less 50 meters long, collapsed;

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BRGY. CAWILIHAN, LEON

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Landslide debris flow into Sibalom River may cause damming, and its sudden breaching may cause flashfloods dowstream.

THE GOOD NEWS!!!

• THERE WERE NO CASUALTIES IN BRGY. CAWILIHAN DESPITE THE SEVERITY AND EXTENT OF THE LANDSLIDE;

• THE RESIDENTS WERE ABLE TO REMOVE ALL THEIR BELONGINGS INSIDE THEIR HOUSES BEFORE THE LANDSLIDE;

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RELEVANCE OF GEOSCIENCE INFORMATION

• Proper and consistent implementation of the geohazard mapping and assessment program can result to: A. Increased LGU awareness on recognizing the signs of impending geohazard events in the likes of rain induced landslides and floods, B. Make them understand more the dangers posed by landslides and floods, and C. Empowers the community and its populace to respond accordingly to the situation.

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Installation of community-based geohazard warning signages

Miagao, Iloilo

Valderrama, Antique

Orientation on Pre-Disaster Risk Assessment 71

Pavia, Iloilo

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Lambunao, Iloilo

The MGB Geohazards Web Portal www.denr.gov.ph /www.mgb.gov.ph/ pia.gov.ph / essc.gov.ph

Option to download the specific geohazards map (e.g. Masinloc Provide information on susceptibilities of a specific NAMRIA Quadrangle Map Sheet) barangay to landslides and

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Making people aware through IEC

• Conduct of province- and municipal-wide information and awareness campaign • Distribution of IEC materials on geohazards (posters, flyers, comics,videos)

DILG (TAPATAN 2012)

HLURB Seminars

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IN PARTNERSHIP WITH THE OFFICE OF THE CIVIL DEFENSE (OCD), REGION 6

Geohazard Presentation for the LCEs (2012)

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When the community can relate and constantly use the results of disaster preparedness and mitigation programs of the government, the negative impacts of natural hazards can be minimized, and most importantly, the loss of lives can be prevented.

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CONTINUING PROGRAMS AND ACTIVITIES

 Updating of 1:10,000 Geohazard Maps

 Vulnerability and Risk Assessment (VRA)

 1:10,000 Coastal Geohazard Mapping

 Detailed Karst Subsidence (Sinkhole) Hazard Mapping and Assessment

THANK YOU FOR YOUR ATTENTION!