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View the document Natural disasters in the Philippines

Natural disasters in the Philippines

by John TOWNEND

The recent eruption of Mount Pinatubo has once again drawn the world's attention to the Philippines. In this article, an attempt is made to place the recent eruption of the volcano within the context of other natural hazards which the country has had to face in recent years. The timing of this article is also relevant as the Community's relationship with the Philippines has recently been strengthened by the formal opening of a Delegation in Manila. This has followed the gradual development of a comprehensive programme of assistance, particularly aimed at helping the smaller, more vulnerable fanners living in the poorer rural areas. Funding comes mainly through the development budget for Asia and Latin American (ALA) countries.

 

Earthquakes

The Philippines archipelago lies between two of the world's major tectonic plates - the Pacific and Eurasian, with the former drawing closer to the latter at a rate of 7.2 cms per year. As a result an average of 5-6 'imperceptible' to 'perceptible' tremors occur every day. Between 1589 and 1983 there were 63 earthquakes which caused major destruction.

The most significant earthquake of recent times occurred on 16 July 1990 with a magnitude of 7.7 on the Richter Scale. It struck Central and Northern Luzon, claiming the lives of 1666 persons, injuring 3561 and causing damage to property worth more than ECU 275 million. The damage to agriculture alone was estimated at more than ECU 30 million.

A focal point for the earthquake relief effort was Baguio City, in which the loss of life, homes and employment were severe. However, the attention on Baguio tended to draw public attention away from both immediate and long term impacts on the low access, marginal farmers of the high-lands, who themselves are the focal point of one of the EEC project called 'CECAP' or the Central Cordillera Agricultural Programme (ALA 8616).

Amongst the damage quickly identified by the project was the following:

- Accelerated soil erosion or landslips in which farmers had lost up to 90% of their upland cropping land.

- Inundation of rice paddies and communal irrigation schemes, built primarily by farmers with project assistance.

- Damage to access routes from the mountain areas, preventing high value vegetables getting from Kayapa Central to markets in Manila and denying farmers a major source of income.

- Damage to major transport routes, water supplies and buildings including hospitals.

As a result of the projects investigations, the European Community was 5 able to respond quickly, preparing and funding a project soon to be known as the Earthquake Reconstruction Programme (ERP). This will be funded over five years and will have the following components: - An Agricultural Component to assist with the agricultural rehabilitation and reconstruction in seven municipalities of the Central Cordilleras.

- A health component to help with the reconstruction of two provincial hospitals in Nueva Vizcaya and Benguet provinces.

- A strategic studies component to assist with the long-term redevelopment and reconstruction of Baguio City and Dagupan.

 

Typhoons

The earthquake of July 1990 was quickly followed by another natural phenomenon which regularly strikes the Philippines - a typhoon. This compounded the earthquake damage and caused subsequent flooding.

Typhoons, with high wind speeds, accentuate the damage to structures and vegetation. Through excessive rainfall and the flooding which accompanies them, they inflict heavy damage on agricultural crops, accelerate soil erosion, damage private and public property, and cause loss of life whilst disrupting commercial activities.

Storm surges are also a common feature of typhoons, sweeping away coastal housing, damaging port facilities, - roads, bridges and other coastal engineering structures. Small scale fishermen are particularly at risk, with fishing gear; boats, nets and fish corrals often lost, damaged or washed out to sea. Ricefields and vegetable farms close to their homes may also be inundated with harmful salt water.

The typhoon season in the Philippines stretches from July to December. During the early part of the season they tend to cross the Northern part of the country, but during the latter part (October, November and December) the South and Central Philippines are usually more at risk. There is a 100% probability that at least 4 typhoons will make land fall in any one year, with the probability of 9 typhoons a year as high as 48%. To put this in perspective, an average of 30 typhoons a year develop in the northwestern Pacific Ocean - about 38% of the world's total. No less than 20 of these will enter the Philippines area of responsibility.

 

Volcanoes

Not content with earthquakes and typhoons, the country is also susceptible to volcanic activity, as recent events have confirmed. The Philippines has more than 200 volcanoes distributed along 5 volcanic belts. Until June 1991, no less than seventeen volcanoes were considered active and now we can safely raise that number to eighteen.

After a rest period of 600 years, Mount Pinatubo showed its first sign of awakening on 2 April 1991, in the form of small scale steam explosions scattering 'cold' dust over the upper flanks of the volcano. Monitoring equipment was promptly installed by PHIVOLC's (Philippines Institute of Volcanic Studies), and on the 6 June, local earthquakes began to increase dramatically.

This was followed by new explosions on 8 June by which date, scientists had declared a high probability of major eruptions and recommended evacuation of the area within a radius of 20 km. This area included the forested and deforested slopes around the volcano, home to around 30 000 indigenous negritos tribal ! people known locally as 'Aetas', as well as the residential quarters of the Clark, Airbase.

The explosive eruption of fresh volcanic material began on 8 June 1991, followed by the first really violent explosions on 12 June and sustained emissions of extreme violence and great volume on 14 and 15 June, when volcanic ash and larger projectiles were thrown to a height of about 30 km, out of the atmosphere and into the stratosphere. At the same time, giant pyroclastic avalanches descended the major valleys to a distance of 20 km, filling the deeper canyons with lahar (lava and ash) to a thickness of over 100 metres.

Fragmentary materials from the volcanic eruption column fell most thickly in the main downwind sector between south and west with a thickness of up to 25 cm on coastal settlements at a distance of 35 km from the volcano. This caused widespread collapse of roofs. In Angeles City (population 280 000) located 2025 km east of Mount Pinatubo, ashfalls accumulated to a thickness of 8-10cm, resulting in the collapse of 5-10% of the roofing structures.

Major evacuations took place before the cataclysmic eruptions of 14-15 June. At the onset of this phase, evacuation of the much larger population within 30 km was recommended, and the danger zone was temporarily extended to 40 km, when the possibility of a massive debris avalanche was recognised.

The climax of the eruption removed the summit of the mountain, opening a crater ' 2 km in diameter. According to a preliminary estimate, some two cubic kilo- . metres of fragmentary unconsolidated: material was ejected, making this the world's largest eruption since 1912. In terms of evacuees the number (well over 200 000) was three times larger than any previous historical evacuation due to volcanic eruption.

The climax coincided with the passage of the first typhoon of the 1991 rainy season nicknamed 'Diding' from which the heavy rainfall generated large mud flows which swept away several major road and railway bridges as well as widening the deep river channel through the centre of Angeles by as much as 80 metres. In the process the Angeles City General Hospital was demolished.

As the typhoon passed from the East, between Baguio City (close to the epicentre of last year's earthquake) and the volcano, the centre-winds of 80 kph rotated counterclockwise, blowing the lower portion of the ash column to the south and south-east, onto the City of Metro Manila. On Saturday 15 June, 'night was turned into day' and about I cm thickness of ash was deposited throughout the city, closing the International Airport for a further five days. On the positive side, the heavy rain which followed helped to settle the fine dust and to wash away some of the thinner deposits.

Since then, the explosive eruptions have continued at a reduced but still impressive level through to the present date, ejecting ash and large fragments to a height of 5 to 19km. Winds blowing predominantly north-eastward between 20-25 June, caused an accumulation of a further 8 cm of air fall deposits at 30 km distance from the volcano (indeed-Pinatubo is now gaining the reputation of being a 'democratic' volcano depositing ash 'one day on Tarlac, the next day on Pampanga and the day after on Zambales province').

 

Damage assessment

During the week of 21-27 June, a major effort was made by the relevant government departments to collect comprehensive statistics. As of 28 June 1991, the casualty count was 289 dead, 39 missing and over 300 injured. Considerable uncertainty remains over these figures because of the difficulty in determining exactly how many nomadic Aeta tribespcople had been living in the area and had perished.

Economic losses as of 28 June include over 16 000 houses destroyed and more than 19 000 damaged, mainly roof collapses. Infrastructural losses (bridges, roads etc.,) have been estimated at ECU 45m. Damage to schools amounts to about ECU 26m.

The cost of rehabilitating agriculture (not including loss of production) has been assessed at ECU 35m. These figures are believed to include the major components, but are not yet comprehensive for all sectors and all parts of the area likely to be affected in the near future. They will therefore be subject to increases, especially due to the dynamic nature of the eruption and the risk of further typhoon damage as the rainy season progresses.

It helps at times of adversity to know that the international community is sufficiently concerned to make a meaningful gesture of support. So far the European Community has quickly made available, ECU 300 000 of emergency aid through the Delegation in Manila. Also Mr Alistair Macdonald, Development Counsellor and the author made a visit to the slopes of the volcano with senior officials from the Ministry of Agriculture on 26 June to see the damage at first hand. The visit was confined to the Southeastern and North-eastern slopes of the volcano, where access routes hand not yet been destroyed. (The photographs accompanying this article were taken on the trip)

The first thing that made an impression was that the deposit of ash is likely to continue for some time; up to three years according to some informed sources. The final inundation of damage will therefore depend very much upon weather conditions, and the amount of debris which continues to be ejected.

The fact that the eruption took place at the onset of the main rains and typhoon season implies that the next few months will be critical in determining the concentration and spread of debris.

The main source of damage will be physical, caused largely by inundation and movement of sediment down the main drainage channels from the mountain. Preliminary analyses suggest that the ash is not as acid or hostile to crop growth as was originally anticipated. The inclusion of material from the sea bed in the ejecta has ensured that more than a moderate amount of lime is present, not only giving the impression of snowfall, but ensuring that the ash is already relatively fertile. The pH of initial samples handled by the Department of Agriculture appear well within the normal range for plant growth (pH 6-7), and containing significant quantities of calcium, silica and iron. This explains why on the field visit, little evidence of 'leaf scorch', especially where inundation was light, was seen.

The initial damage to crops, fodder supply for livestock, buildings, infrastructure, and watersheds was noted. Coconut, banana and other fruit trees were bent under the weight of sediment, leaves covered in a film of 'cement'. Rice and sugar-cane fields were damaged according to the level of deposition, varying from 10-15cm to 15-30 cm in some places. Of some concern must be the risk of inundation of the major rice growing areas of central Luzon.

Of more immediate concern was the lack of fodder supplies to feed animals. Many examples of livestock being slaughtered to capitalise upon their existing carcass weight were encountered. Also there is a danger that the buffaloes (carabao) will become so weakened, that they cannot plough rice paddies in the coming rainy season. High value vegetable growing areas, at altitude on the already fertile weathered soils on the slopes of the volcano will have been destroyed.

Clearly it will be some months before the overall damage picture can be clarified, with the next few months of the rainy season perhaps the most critical. During this period, thoughts must remain with the rural poor Filipinos, hit once again by a natural disaster. Yet at the same time there is a certain admiration for the rapid and well coordinated response of the local authorities which has taken place so far. Their efforts have certainly lessened the loss of life, and done much to help the displaced communities rendered home less by the eruption.

J.T.