Landslides and Flooding
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2017/11/17 Welcome Delegates to the 53rd CCOP Annual Session!!! October 16 – 19, 2017 “The Role of Geosciences in Safeguarding Our Environment” 1 2017/11/17 Cebu City 2 2017/11/17 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 3 2017/11/17 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) 4 2017/11/17 Tectonic Map of the Philippines Source: PHIVOLCS Negros Oriental Earthquake 5 2017/11/17 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. 6 2017/11/17 1:50,000 TIGBAUAN QUADRANGLE (ILOILO & ANTIQUE Province) 1:50,000 LANDSLIDE SUSCEPTIBILITY RATING 7 2017/11/17 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) 8 2017/11/17 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 9 2017/11/17 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) 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 10 2017/11/17 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 11 2017/11/17 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 12 2017/11/17 Day Care Center and Ricefields, Brgy. Buenavista, Tubungan, Iloilo (2011) 13 2017/11/17 Head Base Approximately 10.5 hectares of farmlands were affected/ destroyed by the a landslide in Brgy. Buenavista, Tubungan, Iloilo. (2011) 14 2017/11/17 A hectare, more or less, of farmland affected by a landslide in Brgy. Signe, Igbaras, Iloilo. (2011) Affected area Affected area Ricefields affected by flooding, bank scouring and erosion, Brgy. Frantilla and Wayang, Miag-ao. 15 2017/11/17 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 16 2017/11/17 BACOLOD NATIONAL HIGH SCHOOL, MIAG-AO, MAY 2011 BACOLOD NATIONAL HIGH SCHOOL, MIAG-AO, AUGUST 2011 17 2017/11/17 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.) 18 2017/11/17 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. 19 2017/11/17 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. 20 2017/11/17 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) 21 2017/11/17 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 22 2017/11/17 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 23 2017/11/17 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 24 2017/11/17 In June 2008, Typhoon Frank hit Iloilo Brgy.