Alternative Local Disaster Countermeasures for Agos River, Infanta Quezon

Resito V. David1, Jessie C. Felizardo2

1Project Director, PMO-Flood Control and Sabo Engineering Center, Department of Public Works and Highways, Manila, Philippines 2 Engineer, PMO-Flood Control and Sabo Engineering Center, Department of Public Works and Highways, Manila, Philippines

Abstract

Three successive typhoons from November 13 to December 03, 2004 crippled the coastal towns of Real, Infanta, and General Nakar in Quezon and Dinggalan in Aurora. Extra ordinary heavy rains had brought flash floods, landslides, slope failure and debris flow which devastated the communities leaving numerous death and damages to properties. Due to the magnitude of disaster, the paper limited the discussion on Agos River which affected Infanta, Quezon, where three meter high flash floods rampaged the communities.

In preparation of the rainy season, non-structural measures using local resources and means help lessen the danger pose by the unpredictable inclement weather. Local warning system engaging the participation of the residents, disaster awareness and evacuation procedures through timely information with the aide of hazard maps, establishment of evacuation centers in safe places, and reforestation of the basin are the urgent alternative suggestions to gnawing fear of another disaster.

Key words : warning system, hazard map, accessibility, information dissemination, community participation

The Disaster

On 29 November 2004, 342 mm rainfall was recorded at the PAGASA synoptic station. Between 6 to 7 pm, flash floods swept through Infanta, Quezon. Approximately 3 meters of flood rendered thousands homeless. Flashfloods came with drifted logs, uprooted trees and mud. Agricultural fields and irrigation canals were buried. The entire livelihoods were washed out and most of Infanta’s residents were left with no means to generate income for a number of days.

The rainfall collected by PAGASA synoptic station in Infanta, Quezon was from 8 am to 5 pm. of that day. Thereafter no data was available since the rain gauge was submerged by flood. This intensity is equivalent to 15 day rainfall of November (1951-2002, PAGSA annualized rainfall data)

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From the website of 2005 NINFA Z. BITO The summary of damages1 are as follows :

o 176 casualties, 112 recovered bodies, 53 reported missing, 11 injured, 12,007 affected families.

o 16 out of 36 barangays were severly damaged.. Php 103.3 M damage to agriculture

o Crops, livestock, etc PhP57.5 M o Fisheries PhP 46.7 M

4,256 houses damaged o 1,592 washed out

1 Report from the Infanta, Quezon Municipal Engineering Office

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o 3,674 partially damaged

Damages to public infrastructures and utilities/facilities amount to PhP300 M. total damages to private properties, ecology, are still unknown. Infanta is one of the oldest towns in Quezon Province. It is situated in the northern tip of Quezon mainland lying along the coast of the Pacific Ocean. It is approximately 144 km northeast of Manila. It is a solid plane at the foothill of the Sierra Madre Mountains with a total land area of 342.76 km² and with a population of 58, 580 (2004 cencus) scattered among its 36 barangays with density of 419 per km2. 7 urban and 29 rural barangays comprise the municipality. The Average annual income: is Php 38, 492, 522.83

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Source : Central Intelligence Agency (CIA) Date 01 Oct 1993

Geology Infanta is located in fluviatite alluvium composed of unconsolidated clay, silt, sand, gravel, cobbles and boulders derived from weathering and erosion of pre-existing rocks. The zone is broad alluvium plain. The highest elevation of this zone is 10 meters and the lowest elevation is 5 meters with slope of 0-2%, reckoned from the mean seal level.. Two normal faults have been observed at the western side of Infanta, one almost north south,

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starting from Gabriesl Point to Tacligan Point and other along Agos River suggesting that Agos River is fault-controlled1. Geography Infanta lies on the northeast cost of Luzon east of Sierra Madre Mountain Range, which runs on the Eastern Luzon on the provinces of Cagayan, Nueva Viscaya, Laguna, Rizal to Quezon. Climate The climate of Infanta, Quezon belongs to Type II. The Philippines climate follows Corona Classification described below. Type I Two pronounced seasons, wet form June to October and Dry from November to

May Type II No Dry season but a very pronounced period of maximum rainfall from

November to February Type III No pronounced maximum rain period but relatively dry from November to May Type IV uniformly distributed rainfall.

1 Santos, Teodoro M. PhD, et.al, Summary of Observations During Reconnaissance Survey of Damaged Placed in the Disaster Areas Towns of Real, Infant, General Nakar and Aurora Province with Focus on Bridges and Rivers 2005.

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Source : Study for the Preparation of Flood Control Manual for DPWH Technical Standards and Guidelines The River System Agos River Basin covers the towns of Infanta, Real, General Nakar in the Quezon, Tanay, Antiplolo and Montalban in the province of Rizal. The river discharges to the Pacific Ocean. The catchment area is approximately 928 sq. km., reckoned, 300 meters downstream of the Infanta-Gen Nakar Bridge. It has two major tributaries upstream; the Kanan and Kaliwa Rivers. Kanan river lies on the Real, Infata while the Kanan River flows from Gen Nakar and surrounding municipalities in Rizal.

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Source: PMO-FCSEC Jurisdiction Map

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Land Cover

The land cover of the basin is predominantly woodland. Small percentage of coconut plantation and grass lands are spread over the basin. The downstream area is predominantly built up, with mixtures of agricultural lands on the outskirt and residential areas. Mangroves grow on the deltaic portions.

Logging has been banned in the mountains around the worst-hit towns of General Nakar, Infanta, and Real for 30 years, but the stress from human encroachment is relentless1.

1 Copyright 1995-2005 - TerraDaily. AFP and UPI Wire Stories Agence France-Presse and United Press International.

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Source : NIA GIS Cause of Disaster Anticident followed by a weeklong rainfall from November 13, 2004 caused by four typhoons Unding (international Name Mufia), Winnie (Nanmadol), Yoyong and Zenyang triggered flash floods, slides and sediment movement. On November 29, the rainfall intensity reached its maximum which brought three meter deep inundation in the town proper of Infanta and General Nakar, Quezon. Meanwhile, Real, Quezon was ravaged by flowing debris, slope failures and landslides. Reports attributed the disaster to illegal logging, and slash and burn practices of the farmers, which destabilized the top soil. Old forests were converted to agricultural lands.

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Unstable strata, according to some geologists, is due to the fault lines along Infanta and adjacent municipalities.

Tons of Logs and Debris flowed down from the mountain.

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Accessibility during the disaster The recent past disaster left the town isolated as massive slope failures and land slides were induced by heavy rainfall and carried by the rampaging water, washing out and burying the populated low lands. Mud, uprooted trees, drift woods and other debris were everywhere. The disaster areas’ accessibility for a couple of weeks or so was very limited. Rescuers ventured by foot on muddy roadway blocked by boulders and debris to reach the area. Vehicles could not enter to deliver the relief goods and the badly needed medical services. Floating logs filled up the coastlines and the sea preventing any incoming ship or bancas. The only means were choppers owned by NGOs, US and Philippine Military, and other organizations. Urgent Countermeasures It is a common belief by the residents and municipal officials that the flash floods that occurred directly hit the town proper from the river when the 300 meter retaining wall on the right bank was breached at the height of rainfall. The flow diverted from the river to the town as the collapse of the wall and the scouring of the banks took place. The bridge connecting towns of Infanta to General Nakar and its approach, located just upstream of the retaining wall, blocked and retarded the accumulating logs and sediment as carried by the runoff. The overflow on the bridge and the impact of the runoff rampaged and devastated the nearby communities. The local government of Infanta sought the help of the national government to highly prioritize the rehabilitation of the retaining wall out of fear of the recurrence of flood in the coming rainy season. The Philippines suffers from budget deficit for considerable years. Infrastructure development relies heavily on foreign assistance. The shift of focus of international donors will delay any relief in terms of grants for infrastructure countermeasures. Locally, funds are drops in a bucket to initiate any hardware solution in consideration of the degree of work to be done. This predicament places the municipal government in quandary.

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Breached River Wall where the Flow Passed Directly to The Community The main river course of Agos is changeable due to the shifting sand bars in span of years without any channel maintenance by dredging. In addition, the recent disaster has caused insurmountable unstable sediment on the hill slopes and beds of the river which may flow down any time with significant rainfall intensity. The amount of remnant uprooted trees and driftwoods on the hillsides are still unaccounted at present. Any low value countermeasure introduced may be ineffective in relation to the big catchment area of the river. Comprehensive studies have not commenced yet to determine the actual sediment yield and discharge since the disaster last year. Meanwhile, the residents face impending danger as the rainy season approaches. Alternative Countermeasures For a couple of weeks, the disaster has gained international attention from different donor countries until a Tsunami occurred in the South Asia. The tsunami which crosses intercontinental coasts eclipsed the Quezon tragedy in the magnitude of losses to lives and damages in coastal nations. Foreign aids were shifted to more severe tragedies. Any effective hardware measures are improbable within the five year period. Affordable community based approach to disaster prevention and countermeasures are feasible at present in response to impending disaster. Rainfall and Water Level Data Measurement

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Rain triggers runoff and movement of unstable sediments and logs from the hillside. Determination of the amount of rainfall while in the cloud is realistic in developed countries. However, in the Philippines there is no radar instrument to predict the amount of rainfall due to the operation and maintenance cost it requires. The catchment area of Agos River transcends boundaries of three provinces covering the city of Antipolo, towns of Tanay and Montalban in the province of Rizal, and Real and Infanta in Quezon. Collecting the data from the administrative jurisdiction of the basin requires concerted effort and cooperation between these city and municipalities. Usual practice is to monitor the rainfall and the river stages during rainy season especially during storms. Upstream of Agos River is mountainous which is subjected to orographic lifting and point rainfall while the downstream is flat as it is on the alluvial plain prone to flash floods. Ideally, key observation points are strategically accessible for operation, maintenance and for more accurate representative data. Agreement and cooperation among the municipalities concerned should be established to ensure smooth observation operations and exchanges of the available real time information. Tipping bucket or rainfall collecting device such as ordinary bucket will suffice to determine the real time rainfall. It is preferable to use simpler observation method rather than sophisticated ones due to its cost and maintenance involving imported spare parts. Rainfall gauges are commonly distributed in the catchment basin for more reliable information while the staff gauges can be placed at the junction of Kanan and Kaliwa Rivers, tributaries upstream of Agos River, and on the pier of the bridge connecting Infanta and General Nakar. Lag time is determined lag time for warning operation. Hydrological study based on the new topographical features is not yet surveyed. Observers are preferably living by or near the gauge sites and are essentially trained to read, calibrate the instrument and are able to relay any information at the right time to agency concerned. Operating procedures are documented in layman’s term and pass-on-able. As much as possible, more people are trained and can understand the operating procedures. Information and Communication With the proliferation of cellular phones, communication even in far flung areas becomes more convenient. A central monitoring station will be the information receiver and repository for dissemination to the affected areas. Barangay (smaller administrative body within the municipality or city) headquarters are sub monitoring stations responsible in their jurisdiction, the adjacent and downstream affected barangays. Any information from the barangays are relayed to the main headquarters. Warning System Indigenous means of relaying the message to the people to alert and mobilize them to safer place at the earliest is the main objective of the warning. Roving volunteers from barangays on bicycles, patrol cars, motorcycles, motorboats and horses on rugged terrain

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can disseminate the information and alert the people. Use of people is more reliable than the instruments and equipment such as remote sirens and. electronic boards, where the municipality has no luxury to procure. The disadvantage of using the latter is when power failure hit the municipality, the instruments become non-functional. Locally, the solar panels are very costly and are frequently subject to theft To distinguish the persons in charged of warning, uniforms, for example may be worn by them with hand carried megaphones with sirens for any announcement or alert information. Slope Failure and Landslide Warning System In the Philippine context, slope failure and landslide are basically the same. Technically, landslide is slow movement with gentler slope and can be observed by stages while slope failure is faster movement on a steeper plane. Although, the densely populated area is on the plain, some are living in or near the slopes of the mountains. Compared to the victims in Real, Quezon where most of them were buried by landslides and slope failures, the Infanta victims were due to the flash flood. Foreign technology uses tensiometer and piezometer attached to the computers. Any change in the soil and water pressure is an indicator of impending or ongoing slope movement. Detecting and predicting land slides and slope failures using indigenous means need further study. Installation of instruments may be planned in the future. However, it is more appropriate to avoid the critical slopes and debris flow path by relocating the residents to safer places. Observation also on the debris flow can be reported to central monitoring station to warn the people downstream. Disaster Preparedness Education Part of educating the people is by the use of visuals on boards in public or conspicuous places such as school entrances, compound of municipal halls, hospitals, barangay headquarters, main thoroughfares and others. Warning signs and evacuation procedures in caricatures understandable by the general public are normally depicted. Leaflets, flyers and comics are useful materials to elucidate the warning alert levels, evacuation procedures, the danger zones and other information. The system established in Camuigin Island, another disaster area in the southern Philippines, is worth replicating and can be modified to suit the culture of the local people. Flow of information was briefed to the people involved; from the municipal and the barangay officials down to the lowest rank. Series of training and orientation on the mechanics of the warning, evacuation system and relief operations were explained at different venues with different groups and ages. Dry runs of warnings and evacuation

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drills are the forms of familiarizing the town folks of the system. Rehearsals were carried out on different occasions with the participants playing their actual roles in case of actual incidence. Hazard Mapping. The November 29, 2004 incident has brought the densely populated barangays of Infanta inundated since these areas lie on the alluvial plain. Wide scale flood have swept the town of rainfall intensity equivalent to 342 mm for around nine hours. The extent of flood can be determined through interviews with the residents. However, distinction of the hazards brought about by different rainfall intensities and flood levels are quite difficult presently due to insufficient resources. Some barangays have rough drawings of maps covering their territorial jurisdictions. Roughly the extent of different flood depths can be indicated on the map as related by the residents. Delineation of severity of damages can be also reflected in the maps. Temporary production of these materials is made available to the public and as a future reference for detailed hazard mapping. Although subjective judgment can not be avoided in the determination of the hazards in the area, this can be minimized if standard method is employed. Hazard mapping in the country is not that popular and few people refer to this kind of map. However, this can be used for visual presentation and information dissemination in preparation for disaster prevention. Tsunami Warning East of Infanta, Quezon is the Pacific Ocean, which makes it prone to tsunami. Susceptibility of the place may be lesser compared to other locations in the Philippines since Polillio Islands is located east of Infanta, which may block the incoming wave from the Pacific Ocean. However, tsunami warning may be considered in the very near future. Mobilization and Evacuation Centers During the flash floods, people stayed on rooftops until the water subsided. Most of the buildings are two storeys and very few are higher. Some school buildings were also damaged and can not be safe places for evacuees. Higher elevation should be identified as alternative evacuation centers. It is recommended to build evacuation centers in each barangay with proximity to residents and easily accessible which can accommodate bigger number of people. On the process of rehabilitation, some school buildings and other public facilities should be constructed higher than two storeys. Access to medical services, food supplies, beddings, health hygiene, and lights are indispensable.

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The municipal government can start considering emergency bancas or rubber boats stationed on strategic places to be used in case high water is experienced to rescue and transport people to evacuation centers. As early as the warning is given by the proper authorities, people should start to head towards the evacuation center specially those in the high risk zones. Accessibility During Disaster Relief Operation As mentioned earlier, landslides and slope failures have isolated the towns of Infanta, Real and Genaral Nakar from the rest of Luzon Island for many weeks. Bridges were destroyed, all roads leading to the towns were blocked by boulders, uprooted trees, and sediment debris, and the seashores were filled with floating logs. Transportation by land was impassable and sea was not navigable. Clearing operations were done by heavy machines with the concerted efforts of government and the local NGOs. Donations from foreign countries in terms of heavy equipment relieved the affected municipalities. At present it is quite difficult to suggest alternatives to sea and land transportation in case similar magnitude of damages recurs. Building new roads does not guarantee isolation because of the random probability of landslide occurrence and it requires huge amount and time. An immediate alternative is the quick clearing of the roads in case of similar incident with the stand by equipment to allow emergency passage of any aid or assistance.

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Source : Philippine Star, December 1, 2004

Blocked Roadway by Debris From Slope Failure

Relocation At the downstream of Agos River, high velocity flows with sediment and floating logs have eroded river banks and breached retaining wall which directed the runoff to the town proper. The area is unprotected while the wall is not yet rehabilitated and no countermeasures are introduced. Places highly vulnerable to disasters are to be avoided as residential areas. In anticipation of the heavy downpour, the high sediment yield due to slope failure, landslide and the remnant uprooted trees and logs on the hills, flood plain should be vacated.. It is ideal to have hazard maps as basis for identifying and establishing the relocation area, however, in its absence the knowledge and experience of the residents can be sought. In light of the safety of the residents, land use and zoning regulations should be formulated and established with reference to the hazard maps. The planned land use will serve as the blue print for resettlement which may require more than a decade to be realized. As a starting point, the residents of the severely devastated places should be resettled to safer locations. Community Participation

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In a meeting held at the municipal hall of Infanta, Quezon, the municipal government officials mentioned that they can mobilize their constituents on a voluntary basis to help in the channel works. Mud and logs deposited on the community were hauled and by the town folks for several weeks through labor intensive and later with the assistance of NGOs with modern machineries. Roadways were cleared of mud and the spoils were deposited on vacant lots. Logs mostly with high commercial value were scattered around the community. These were salvaged, chain sawed and used to repair the damaged dwelling places. Others were made into furniture. The breached retaining wall, which was the urgent concern of the municipal engineers, may be replaced temporarily with longitudinal heap of boulders as dikes to armor the nearby community. Boulders abound on the rivers and can be sourced out by quarrying or be carried through labor intensive if machinery is not available. Motivation is required to sustain the work which should be inspired by the municipal officials. Parallel to these activities is reforestation. Civic organizations, school children, government offices, religious entities and other groups may participate in tree planting. However, sustainability and growth of the trees must be ensured. Small percentage of the trees survive after they are transplanted on the site due to lack of monitoring and proper care. On the other hand, aside from the tree planting the residents should preserve the forest by guarding any illegal logging and inhibit any slash and burn practices which induce soil erosion. The Infanta, Real and the towns covering the Agos River basin can emulate and forge the practices in the Palawan Province, central western part the Philippines. People are vigilant to preserve the forest. Active surveillance by the local people of. forest hinders and minimizes the would be violators to pursue their intention. Violators caught are featured in the media and penalized. There is concerted efforts between the residents and the local government.

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Street Cleared with mud. Marks of mud deposit still fresh on the fence wall Conclusion The political and socio-economic turmoil prevailing in the country dampened the hope to implement comprehensive infrastructure measures in Infanta, Qeuzon. Meanwhile it is indispensable to formulate alternative plans that can be achieved by the available resources in anticipation of the inclement weather. Understanding the basic questions of what, where, when, and how of disaster mitigation lessens damages to properties and lives. The Infanta, Quezon proposal shall include identifying the safe places for evacuation, increasing the awareness and alertness by education and drills and mobilizing the people immediately as soon as the warning started, relocation of residents to safer areas, and community participation in the reforestation and rehabilitation of the municipality. Likewise, evacuation centers responsive to the needs of the weaker gender and children include privacy, health and sanitary provisions, sufficient supply of food, medical services and others. References Flash Flood and Debris Flow Disaster Prevention Manual for Camuigin Island, Earth System Science Co., Ltd., Center for Disaster Preparedness, Foundation, Inc., Pacific Consultants International, Philippines, 2005.

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Philippine Star Draft Field Report: Philippine Flooding/Typhoon Rapid Environmental Impact Assessment, Ole Danbolt Mjoes, Hazard Research Center, Norwegian Nobel Committee, 2005

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