Faculty of Arts, Cultures and Education | University of Hull

Disasters, 2003, 27(3): 95–109

Constructing Vulnerability: The Historical, Natural and Social Generation of Flooding in Metropolitan Manila Greg Bankoff Wageningen Univ and Univ of Auckland

Flooding is not a recent hazard in the Philippines but one that has occurred throughout the recorded history of the archipelago. On the one hand, it is related to a wider global ecological crisis to do with climatic change and rising sea levels but on the other hand, it is also the effect of more localised human activities. A whole range of socio-economic factors such as land use practices, living standards and policy responses are increasingly influencing the frequency of natural hazards such as floods and the corresponding occurrence of disasters. In particular, the reason why flooding has come to pose such a pervasive risk to the residents of metropolitan Manila has its basis in a complex mix of inter-relating factors that emphasise how the nature of vulnerability is constructed through the lack of mutuality between environment and human activity over time. This paper examines three aspects of this flooding: first, the importance of an historical approach in understanding how hazards are generated; second, the degree of interplay between environment and society in creating risk; and third, the manner in which vulnerability is a complex construction. Keywords: Philippines, vulnerability, flooding, urbanisation, history. The state of the Philippine environment in the new millennium is not encouraging. Prey to frequent seismic and climatic hazards, buffeted by the vagaries of 381 years of colonial misappropriation followed by the much more ruthless exploitation of international market forces and having a population of around 80 million, the country suffers from severe environmental strain in part manifested by the increasing magnitude of floods. On the one hand, this phenomenon is related to a wider global ecological crisis originating in climatic change, ozone depletion and the rapid loss of biological diversity, but it is also the effect of more localised human-induced activities. A whole range of socio-economic factors such as land use practices, living standards and policy responses are increasingly influencing the frequency of natural hazards such as floods and the corresponding occurrence of disasters. In particular, the reason why flooding has come to pose such a chronic risk to the residents of metropolitan Manila has its basis in a complex mix of inter-relating factors that emphasise how the nature of vulnerability is constructed through the lack of mutuality between environment and human activity over time. Rainfall, topography and subsidence combine with demographic increase, urban growth and the volume of waste products to prevent runoff and impede drainage. Even the palliative measures taken often only shift the locale © Overseas Development Institute, 2003. Published by Blackwell Publishing, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA.

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of disaster from one area to another, usually to the disadvantage of the more socially vulnerable without addressing the root causes of that condition. Rather than regarding floods as purely physical events requiring largely technological solutions, they can be viewed primarily as the result of human actions. Terry Cannon persuasively argues that while hazards are natural, disasters are not. Social systems generate unequal exposure to risk by making some people more prone to disaster than others and that these inequalities in risk and opportunity are largely a function of the power relations operating in every society. Critical to discerning the nature of flooding in Manila, then, is an appreciation of the ways in which human systems place people at risk in relation to the environment and to each other, a causal relationship that is now mainly understood in terms of an individual’s, household’s, community’s or society’s vulnerability (Cannon, 1994: 14–15, 19). Above all, though, it is also an historical process. Only through a perspective that pays attention to changes in topography, demographic growth and urban development over time can the measure of flooding in the metropolitan area truly be gauged. It is the interplay between these three — history, nature and society — that determines how the vulnerability of the city’s inhabitants is constructed.

Climate and history Any appreciation of the nature of floods in the Philippines first requires an understanding of the impact of typhoons on the archipelago’s climate. Each year about 20 typhoons cross the Philippine Area of Responsibility (Brown et al., 1991: 196). A distinction should be made between ‘remarkable’ or destructive typhoons and the more ordinary variety of tropical cyclones. The former are ‘one of the greatest natural calamities that may occur in any place’, while the latter are responsible for much of the rain that makes the climate so ideal for agriculture (Coronas, 1920: 446). While tropical cyclones can occur in any month of the year, they are much more frequent between July and November and very rare between January and March. Just as significant as this seasonality are the routes taken by tropical cyclones and the consequences for various parts of the islands. At least five main tracks have been identified: one that crosses to the north of Manila; one that traverses south of the capital; one that passes east or north-east of the archipelago either disappearing or recurving in the Pacific; one that forms in the China Sea to the west of the Philippines; and another that re-curves in the China Sea between the parallels 10º and 20º. As a result, some provinces are more frequently exposed to typhoons than others. A comparative historical analysis of the total number of tropical cyclones experienced by each major region of the archipelago reveals that northern Luzon receives by far the highest number but that there is little difference between central Luzon, southern Luzon and the Visayas, although two islands in the latter, Samar and Leyte, figure among the 10 most exposed provinces. Mindanao, on the other hand, presents a very different profile with fewer tropical cyclones and a higher percentage of milder events proportionately than any other region (Census, 1920: 1, 462). This pattern of tropical cyclones is important to understand both the intensity and regularity of flooding in the Philippines as they constitute up to 38 per cent of annual average rainfall in the archipelago, especially during the latter half of the year (BAS, 2001: 9). Historically, floods are the source of much privation and suffering and are largely of two types: the sudden raging torrent that peaks sharply and dies away

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quickly as a result of localised rainfall, and those of a much more widespread nature and longer duration usually associated with persistent rainfall. The minutes of local ‘town chronicles’ give frequent accounts of such hazards in the past (Bankoff, 2003: 41–51). A list drawn up from these sources found in the Archive of the Manila Observatory constitutes a record of major floods that occurred between 1691 and 1911. While almost certainly incomplete, it does provide an indication of the primary causes, geographical predisposition and even the frequency of such events in specific areas. In particular, the chronicles regularly refer to flooding in connection to the passage of tropical cyclones; over 56 per cent of all recorded incidences are directly attributed to typhoons (AMO, Box 10-37). On other occasions, floods are mainly attributed to heavy rainfall and the monsoons. Moreover, the close association between flooding and typhoons suggests a certain seasonality in the their occurrence that corresponds to the peak in the latter’s annual cycle between July and November. The geographical predisposition to flooding is even more tenuous to gauge as the records largely reflect the principal centres of Spanish colonial power. Still, the preponderance of the northern part of Luzon over the rest of that island is consistent with the higher incidence of typhoons there. Some idea of what the incidence of floods on local communities might mean can be estimated by closer scrutiny of the more complete local chronicles that suggest how often people were faced with such situations. The records for Nabua in Camarines between 1691 and 1856, and those for Pangasinan 1768–1872 depict just how frequent a life event floods were. In Nabua, a person experienced one such event every 9.7 years on average but once every 5.6 years between 1733 and 1800 (AMO, Box 10-37). Other local histories present a glimpse of the reality of this hazard for communities. The rising of the Abra River to a height of more than 25 metres above its normal level caused over 1,800 deaths on 25–7 September 1867 or, again, the flood in Santa Maria, Ilocos Sur destroyed the barrio of Sumagui, carrying away more than 22 houses and causing more than 100,000 pesos worth of damages in 1911 (AMO, Box 9-35). Nor has the number or severity of floods lessened in recent times. Heavy rainfall led to the submergence of low-lying areas in Pampanga and Bulacan in July 1972, August 1974 and October 1978. Continuous rain killed over 200 people and damaged 200,000 hectares of agricultural land in Mindanao in January 1981 (Brown et al., 1991: 198–9). There was severe flooding during the summer of 1986 and again on 6 September 1995 when the sides of Lake Maughan burst, killing 57 and affecting more than 60,000 people in South Cotabato (NDCC, 1995).1 But the flash flood that overtook Ormoc on 5 November 1991 was exceptional even by Philippine standards. Torrential rainfall at the height of a weak tropical cyclone dumped nearly 150 millimetres on to the denuded mountain slopes above the small eastern Visayan city in a short period. Water levels rose to over six metres in a matter of minutes, while an unusually high tide prevented the flood from running straight out to sea. The whole episode was over in less than 15 minutes but the flood destroyed between 80–90 per cent of buildings, left 5,365 people dead and a further 2,046 missing (Vitug, 1993: 8; Laurel, 1991: 7). Moreover, statistical trends suggest that floods have become more numerous and more devastating in recent years (see Figure 1). Certainly, the frequency of events and the number of people affected have increased steadily as human-related activities such as deforestation, overgrazing and urbanisation aggravate environmental conditions, making communities more vulnerable. The toll, too, has been rising. Floods have been responsible for 1,353 deaths, 423 injuries and 433 missing since

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Figure 1 Number of people affected by floods, 1973–2001 Source: Disaster Data 1973 to 1999 Floodings/Flashfloods (NDCC, 1999) and Disasters in the Philippines 2001 (CDRC, 2001a: 2, 10).

1973. No fewer than 1,563,342 families comprising 8,021,739 people have been affected, 5,133 houses destroyed and a further 14,984 damaged and property and agriculture losses estimated at P7.575 billion ($303 million) (NDCC, 1999). Floods were the sixth-most-common disaster in 2000, affecting 227,306 families or 1,115,344 individuals (CDRC, 2001b: 1–2).

Flooding in Metro Manila Metro Manila is situated in a semi-alluvial floodplain formed by sediment flow from the Meycauayan and Malabon-Tullahan river basins in the north and the Marikina river basin in the east. It encompasses a land area of 636 square kilometres, measuring about 20 kilometres in length along a north-south axis and stretching more than 22 kilometres at its widest. The conurbation is open to Manila Bay on the west and to Laguna de Bay, a large lake, on the south-east. As such, the metropolitan area now constitutes a vast urbanised drainage basin that experiences frequent inundations from overflowing rivers and storm waters that render the existing system of esteros (modified natural channels) and canals constructed during the Spanish and American colonial periods inadequate (Liongson, 2000). Despite the growing vulnerability of much of the metropolitan area, however, rapid urbanisation has continued unabated with residential homes, industries and commercial sites increasingly exposed to flood-related destruction. The administratively designated National Capital Region (NCR) now comprises 12 cities and five towns. Leonardo Liongson and Peter Castro classify flooding in Manila into three types: local, moderate and regional. Local street flooding is the result of intense, sudden thunderstorms over a few city blocks that cause inundations of 20–50 centimetres, light property damage and heavy traffic congestion. Typically flooding


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Figure 2 Per cent of Barangays in Metro Manila by city affected by flood in 2000 Source: Hazard Prone Areas in Metro Manila (OCD, 2000a).

happens because curb inlets, drainage culverts or natural upland ditches are insufficient to handle the sudden volume of water. Such events occur all over the metropolitan area but are more frequent in low-lying areas. Moderate flooding is produced by intense rainfall of over an hour’s duration that is often associated with tropical cyclones and affects a wide area of the city with inundations of more than 30 centimetres. Damage to property can be considerable; there may be isolated cases of personal injury or even loss of life; and whole districts become impassable to vehicle movement. Again, moderate flooding mainly occurs in low-lying areas of the capital. Regional flooding, on the other hand, affects whole cities and may cover several river basins. It is a largescale condition consequent upon typhoons that ensues from heavy rainfall lasting over several days and may be aggravated by high tides or storm surges. All gainful activities are severely curtailed until the waters subside (Tabios et al., 2000: 19–20). While flooding variously affects all areas of Manila, some cities and municipalities are more vulnerable than others due to their location and height relative to sea level. Some 20 per cent of the capital’s 63,600 square hectares is designated as flood prone, of which 5,385 square hectares (41 per cent) are served by pumping stations and the remaining 7,715 square hectares (59 per cent) suffer frequent and longlasting inundation (MMDA, n.d./a). Areas to the east, south-east and south of the capital around Marikina, Pasig, Mandaluyong, Muntinlupa and Parañaque and especially those adjacent to Laguna de Bay such as Taguig and Pateros are acutely susceptible to flooding (see Figure 2). In some particularly exposed cities such as Muntinlupa and Taguig, all barangays (the basic unit of local government) are regularly inundated and the coverage of flooding extends to 88 per cent and 83 per cent of their respective land areas (OCD, 2000a). Flooding affected 162 of Manila City’s 897 barangays in November 1998 causing hardship to an estimated 61,104 families or approximately 305,520 people, fully 18 per cent of the total population (OCD, 1998).

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Unsurprisingly, there is often a positive correlation between flood-prone areas and those cities and municipalities that have larger proportions of low-income residents. Flooding has been a feature of daily life in Manila since at least the 19th century. When rains were particularly strong or tides high, the natural drainage system was unable to cope with the sudden volume of water and the city was turned into one vast lake that its inhabitants had to traverse by canoe. The gradual expansion of the urban area into the surrounding marshes only increased the frequency and magnitude of such inundations: workers in the booming cigar-making factories of Arroceros were distinguished by their high-heeled sandals worn to gain access safely to their places of work (Huetz de Lemps, 2001: 495). More recently, rapid population growth, differences in land usage and environmental factors have combined to magnify the nature and extent of flooding in the metropolitan area. In the 1950s, areas below the flood line of 12.5 metres above sea level in Manila (Tondo, Sampaloc and Santa Mesa) as well as those low-lying barangays in Quezon City, San Juan and Mandaluyong were regularly inundated. Flooding was mainly attributed to natural causes such as flat terrain, rainfall intensity and high tides in Manila Bay. However, even by the late 1950s, activities associated with modernisation such as the spread of urbanisation in the hills to the east of Manila and the encroachment of structures along the banks of the Pasig River led to severe reductions in the width and depth of tidal channels. By the 1960s, almost 70 per cent of the city was subject to floods that ranged in depth from 3.6 to 4.5 metres. The spread of congested neighbourhoods, especially along the banks of rivers and creeks, proved to be especially susceptible to floodwaters that regularly swept away the flimsy housing of the urban poor. Floodwaters reportedly reached a height of 6.1 metres in the squatter colony of Tatalon on one occasion and even lapped across the floors of Malacañang, the presidential residence, on another. The severity of flooding was undoubtedly aggravated by the fast pace of urban expansion, in particular the rise in the number of paved roads and the growth in building complexes that enlarged impervious surface areas and increased the incidence of flash floods. The massive deforestation of the Marikina and Montalban watersheds and the further encroachment and even disappearance of esteros (an estimated loss of 21 kilometres) severely restricted the dissipation of floodwaters (Zoleta-Nantes, 2000: 43–4). By the 1970s, the degree of soil erosion turned floodwaters brown and murky while silt and garbage clogged remaining waterways, further restricting the flow of water. Flooding was perennial in Malabon and Navotas and simply a fact of life to many living in Manila, Quezon City, Pasay and San Juan. Heavy floods left thousands of families homeless and severely disrupted power, communications and transport, forcing many people to have recourse to rafts and small boats as a mode of urban conveyance. Silt deposits reduced the water-holding capacity of Laguna de Bay by 64 per cent while surface run-off from denuded watersheds increased its level by 2.7 metres during the 1980s with dire consequences for low-lying communities along its shores. Matters were only aggravated by the development of new sub-divisions on former agricultural lands in Marikina, Cainta, Pasig, Pateros and Taguig. Floodwater depths continued to rise in the 1990s, especially in the south and south-east and in the northern cities of Kalookan, Malabon, Navotas and Valenzuela. Hundreds of thousands of families regularly required evacuation to higher ground and the subsequent traffic congestion following a torrential downpour turned commuting into a nightmare, trapping some inside their vehicles for up to 16 hours. Floods were usually accompanied by outbreaks of infectious diseases such as cholera and leptospirosis, power outages that paralysed industrial and manufacturing operations and property


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losses that were estimated at P900 million ($36 million) over the period (ZoletaNantes, 2000: 45–8). The first widely recorded instance of serious flooding dates to 1942 when unprecedented high water levels were reported that inundated the city for several days (Fano, 2000: 53). Major floods also occurred in 1948, 1966, 1967, 1970, 1972, 1977, 1986 and 1988 as water overflowed the main rivers and canals. The flooding caused by Typhoon Miding in 1986 inflicted the most serious damage in recent years with floodwaters extending to 103.6 square kilometres or over 16 per cent of the total area of Metro Manila. Flooding in 1988 caused by Typhoon Unsang also inflicted serious but more localised damage in the Marikina river basin and along the low-lying shoreline of Laguna Lake (MMDA, n.d./b). Nor have matters improved much of late: thousands of Manila residents were stranded on the streets or trapped in vehicles all night after heavy rains on 28 July 1995 and major flooding incidents happened again on 28 May 1996 and 18 August 1997 (Page, 2000: 86). Over the past half-century, floods have become both more extensive and more severe. Areas regularly inundated have spread from the low-lying coastal areas to encompass suburban neighbourhoods, newer urban developments and along the shores of Laguna de Bay. Nor have the expensive subdivisions built on former agricultural lands been spared and flooding has even become prevalent in locations with higher elevations (Zoleta-Nantes, 2000: 49). Moreover, water depths have also steadily risen over time making flooding a major hazard to residents and prompting a recent newspaper article to quip that: ‘Though the deluge mentioned in the Bible may be argued as allegorical, the flooding that occurs in Metro Manila streets after a downpour is definitely not’ (Afuang, 2001: B4).

Constructing vulnerability Topography predisposes Metro Manila to flooding. Climate makes the city still more vulnerable: average annual precipitation over the area between 1961 and 1990 varied from 1,834 to 2,257 millimetres, with rainfalls of 200 millimetres or more over a twoday period not uncommon and substantially higher rates recorded in the event of typhoons. The volume of run-off is greatly intensified by the widespread use of bitumen and concrete associated with urbanisation. In many low-lying coastal or riverine areas, flooding is also associated both with tidal variations that can inundate lands above mean sea levels and with poor drainage of alluvial soils in the Marikina valley (Zoleta-Nantes, 2000: 35–8). Over recent decades, moreover, the extent of flooding has been considerably aggravated by the subsidence of the land fringing Manila Bay. The sediments that underlie river deltas have a high water content that is subject to ‘squeezing’ by the weight of succeeding deposits, a process that is greatly accelerated when groundwater is extracted faster than it can be replenished by natural recharge from rain seeping back into the ground. Records taken at Manila’s South Harbour show that mean sea levels rose about two millimetres a year between 1902 and the early 1960s but accelerated sharply thereafter, reaching a rate of approximately three centimetres by 1991. Such an increase cannot be explained as solely a consequence of global warming and bears a marked correlation to the rise in both groundwater extraction and population growth.2 As the land around Manila Bay sinks and the level of the sea rises, flooding has become more prevalent not only in Metro Manila but in the surrounding provinces (Siringan and Rodolfo, 2002: 4; Rodolfo, 2003).

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These climatic and environmental factors that themselves are evolving over time partly as a result of natural processes and partly from human-induced ones also inter-relate in complex ways with the changes brought about as a result of human activity to make Metro Manila more flood prone. Principal among these latter developments is the sheer rise in the size and density of population. Since 1903, the number of people living in the metropolitan area has risen from 328,939 inhabitants to 10,491,000 in 2000, an increase of 3,189 per cent. Population density in the region also rose accordingly from 517 people per square kilometre in 1903 to 3,872 in 1960 and 16,495 by 2000 (see Figure 3). These averages, however, conceal an enormous variation between cities whose densities range from a low of 10,717 people per square kilometres in some areas of Quezon City to 50,042 persons in more congested areas (Zoleta-Nantes, 2000: 40). The sheer weight of human numbers puts considerable pressure on resources that, in turn, has substantial consequences on the environment and intensifies both the severity and duration of floods. Much of Metro Manila’s population increase has come about as a result of massive urban migration since the Second World War as rural folk are attracted to the city by higher incomes and greater livelihood opportunities. Approximately 300 families have migrated to the NCR each month since the 1980s (Zoleta-Nantes, 2000: 40). The level of urbanisation in the Philippines, that is the proportion of urban population to the total, rose from 21.7 per cent in 1950 to 47.6 per 12,000,000

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Figure 3 Population data for Metro Manila, 1903–2000 Sources: Zoleta-Nantes, 2000: 41; OCD, 2000b.

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cent in 1997 (Rebullida, 1999: 16; Ibon, 2000: 66). Most of these people were poor and could not afford the high costs of land, housing materials and construction. Land values throughout the country increased 12 to 15 times between 1940 and 1969 but 27 times in the NCR. In the 1980s, land prices rose 35 to 40 times in Quezon City, 50 to 80 times in Makati, 250 to 400 times in Diliman and a staggering 2,000 times in Escolta. In 1996, the CBD was registering an annual increase of 50 per cent and even the value of land in peripheral areas rose by 25 per cent annually (Rebullida, 1999: 16– 17). As a consequence, migrants have generally had to find accommodation in the informal housing sector becoming interchangeably squatters (illegal occupiers of land), slum dwellers (residing in blighted urban communities) and makeshift dwellers (living in shelters made of scrap materials). Such neighbourhoods are often situated on the urban fringes or wastelands that proliferate in Third World cities, especially near to areas that provide work and along major transport hubs and links. In Metro Manila, the banks of rivers, canals and esteros have frequently served in this capacity. Since the demand for land is at such a premium, spaces that are vacant or only nominally owned by national, city or municipal authorities prove particularly attractive as locales for squatters. The result is that makeshift housing often encroaches on to available waterways, blocking the access of maintenance personnel and equipment from the Department of Public Works and Highways (DPWH) or the Metropolitan Waterworks and Sewerage System (MWSS) and, by a gradual process of accretion, narrows their flow capacity and diminishes the volume of discharge they are able to handle (Labrador and Bualat, 1996–7: 44).3 A recent report submitted by the Office of the City Engineer details the specific histories of how such processes actually occur. How the Estero de Tanque in Paco was partly filled in and is now occupied by adjacent lot owners and squatters; how the Estero Tripa de Gallina in Santa Ana was subdivided and disposed of by the Land Authority to tenants during the administration of President Macapagal; and how a portion equivalent to 1,788.30 square metres of the Estero de Aviles in San Miguel was titled to a certain Arsenio Dy of 3011 Nagtahan, Sampaloc as TCT Nos. 67,425 and 67,426. Nor are squatters and the urban poor the only ones responsible for these encroachments. Thus the Estero de Maytubig in Malate that has been dried up since 1925 is currently occupied by the Agno-Leveriza government subdivision, Bank Plaza and the Manila Zoo among others, or the Estero de Concordia in Paco that is currently included in the private land title of the Manila Gas Corporation (Aboy, n.d.). The extent of the esteros problem is indicated by the number of what are termed informal settler families (ISFs) that were deemed by the DPWH to be in urgent need of relocation before the onset of the rainy season in 2001. Priority areas included 279 families living near or on the Estero de Valanecia, 336 on the Estero de San Miguel, 200 on the Estero de Aviles, 151 on the Estero de Santibañez, 858 on the Estero de Magdalena and 650 on the Estero de San Lazaro totalling 2,474 families and costing an estimated P208 million to relocate (DPWH, 2001). Recent estimates of ISFs living along the banks of the metropolis’s waterways are 27,300 families — or some 164,000 people (Fano, 2000: 59). Unfortunately, the construction of informal housing is not the only environmental problem related to the encroachment and gradual infilling of esteros. Residential communities are primarily responsible for generating about half the total volume of the metropolitan area’s solid wastes. Metro Manila inhabitants disposed of 6,050 tons of garbage daily in 1995 with an annual increase estimated at 2 per cent and were generating on average 0.71 kilograms of waste per person per day by 2000 (Ibon, 2001: 4–5). Only 71 per cent of this rubbish is collected by trucks and taken to landfill centres. The remaining 1,750 or so tons are simply left on street corners, dumped on

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vacant lots or thrown into storm drains, canals, creeks or rivers. Anything from rubber tires to dead animals are disposed of in this manner. A study completed in 1995 found that from 0.9 to 2.6 per cent of people in the NCR, according to age, disposed of their trash in the esteros, the under-30s being far less environmentally conscious than the over-60s (Perez et al., 1995). Altogether, this represents an amount of from 55 to 157 tons of solid wastes each day that clog the network of drainage canals, posing a considerable risk to health and greatly increasing the likelihood of flooding. That such a quantity of waste represents a serious threat to flood-control measures is borne out by the quantity of garbage recorded at the metropolitan area’s various pumping stations and related facilities. Approximately 15,500 cubic metres of rubbish accumulates annually around the capital’s 16 pumping stations and two trash screens, although the volume at any one time can vary enormously from the average 29 cubic metres at Makati to the 4,217 cubic metres at Tripa de Gallina. Although the total amount of accumulated garbage actually fell in 2000, more worrying is the trend that suggests a steady decline in the percentage of garbage that is collected with corresponding risks to the maintenance and efficiency of these stations and their pumps (see Figure 4). The building of pumping stations to facilitate the dispersal of floodwaters represents only one of the ways in which city and municipal authorities have attempted to deal with the problem of chronic flooding within the metropolitan area. As early as 1882, a plan was drawn up for the refurbishment of the drainage system based on the existing network of esteros. Regarded as the only practical scheme given the financial constraints of the time, the project had only been partially realised by the eve of the 1896–98 Philippine Revolution (Huetz de Lemps, 2001: 502–3). A sewerage system was had been constructed under the American administration between 1904 and 1911 but was only designed to serve an urban population envisaged at half a million people

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(Zoleta-Nantes, 2000: 40). Currently responsibility for flood control in Metro Manila depends on the scale and extent of the problem. Localised flooding associated with drainage basins of a few square kilometres are handled by city or municipal officials usually through the construction of gutters and storm drains that direct rain into existing natural or artificial waterways. Major flood-control problems involving issues that affect the entire metropolitan region and nearby watersheds were made the responsibility of the Department of Public Works and Highways in 1987 and the Metro Manila Development Authority since 2002.4 After the widespread flooding of 1972, a major flood-mitigation programme was undertaken, financed by the Overseas Economic Cooperation Fund it resulted in the raising of the Pasig River walls and the erection of the first seven pumping stations, two floodgates and four drainage mains between 1974 and 1978. In 1980, excavation of a 10-kilometre long diversion channel known as the Mangahan Floodway Project (MFP) was begun linking the Marikina River at Pasig (Barangay Mangahan) to Laguna de Bay at Taytay, Rizal. Using the lake as a temporary catchment basin in times of intense rainfall over the metropolitan area to divert 70 per cent of the flow coming down the Marikina River and reduce the likelihood and extent of inundation along the Pasig River, the channel also acts as a reverse flow at times when the water level in Laguna de Bay is higher than that of the river. The Marikina River is one of 13 tributaries that discharge into the lake but there is only a single outlet: the NapindanPasig River that carries water from the lake to the sea at Manila Bay. The flow of water out of Laguna de Bay has been subsequently regulated by the construction of the Napindan Hydraulic Control Structure — locks that open to control the reverse overflow into the lake through the reinforced channel of the Napindan River to accelerate the lowering of its level and alleviate flooding along its shoreline (MMDA, n.d./d). A major dyke is now envisaged to protect the neighbourhoods adjacent to the lakeside running from General Santos Avenue in the south to the Mangahan Floodway in the east. The core of the DPWH flood mitigation works, however, remains its network of drains, canals, esteros and rivers that discharge into Manila Bay. This system consists of 44 kilometres of main drains, 1,200 kilometres of lateral drains, 290 kilometres of canals and esteros and 153 kilometres of rivers and major streams (Fano, 2000: 66). Problems, however, arise with this purely technological solution to the question of flooding in Metro Manila. In the first place, the cleaning and rehabilitation of existing flood-control structures and facilities is both costly and difficult. Some P152 million is spent annually to cover such services and a full-time staff of 446 maintenance crew employed. The impossibility of keeping the esteros clear near major market places and sites heavily occupied by squatters has led to the innovative recruitment of local Bantay estero teams, composed of five to seven labourers, whose sole responsibility is to maintain a specified section of waterway free of garbage (Fano, 2000: 67; MMDA, n.d./e). Nor, of course, can the question of ISFs be simply regarded as a matter of flood mitigation. The eviction and demolition of such communities has serious socio-economic implications and important political ramifications that few elective office holders choose to ignore. In many cases, drainage or maintenance work is suspended because there are informal dwellings. A recent MMDA document cites three examples of flood-control projects not completed for this reason: the dredging of the Estero de Magdalena only 40 per cent accomplished and then suspended on presidential instructions to defer demolition and relocation of informal settlers; the cyclone wire fencing of the Vitas pumping station only 35 per cent accomplished and then suspended because of the presence of informal settlers; and

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the steel sheet pile driving as part of the improvement works on the Estero de Sunog Apog only 54 per cent accomplished and then suspended for the same reason (MMDA, n.d./f). While squatters and ISFs provide useful media scapegoats and are largely blamed for encroachment on the existing waterways system and of impeding cleaning operations, industry, business, government and fish-pen operations are also major contributory agents and just as culpable (Page, 2000: 87–8; Rodolfo, 2003). Moreover, the prevailing assumption that the problem of flooding in Metro Manila necessitates purely technological solutions is often itself a factor in making some sectors of the population more vulnerable to hazard as in the case of the Mangahan Floodway Project: the MFP’s diversion of the overflow from the Pasig River only exacerbates the rising water levels in Laguna de Bay and contributes to the frequency and severity of flooding among shoreline municipalities such as those in Taguig. Nor is it completely incidental that these neighbourhoods also house a large percentage of the metropolitan’s urban poor, many of whom are squatters without legal title to the land their dwellings are sited on.

Conclusion There are three aspects of flooding in Metro Manila that this study illustrates: first, the importance of an historical approach in understanding how hazard is generated; second, the degree of interplay between environment and society in the creation of risk; and last, the manner in which vulnerability is a complex construction. A fuller appreciation of the nature of vulnerability is still often hampered by the lack of an adequate historical perspective from which to understand the contexts and roots of disaster causality (Oliver-Smith, 1986: 18; Lees and Bates, 1984: 146). It is not simply the occurrence, frequency and intensity of environmental events that are significant but their sequence that is of critical importance (Winterhaler, 1980). The relationship between climate, topography, resource use and culture over time is the basis to determining the nature of flooding in Metro Manila as it is to any other location under review. History, far from being a scholarly topic with little practical application, actually provides both the framework as well as sets the conditions within which these other factors relate. Without proper consideration of the temporal dimension, hazards remain random, disasters unaccountable and societies simply exposed. Certain communities or segments of populations are often situated in more perilous settings than others due to the consequences of political, economic and social forces that change over time and in relation to the landscape and its use and to the nature of hazards that also have their own cycles and historical evolutions. Just as history reveals that vulnerability may take centuries in the making, so is the sense of its complex construction important to the way in which disaster is increasingly conceptualised. The notion that hazards are not merely physical phenomena but that human agency is also a contributing factor to their occurrence has led to a considerable extension in understanding how disasters come about and how the root causes of vulnerability lie in a variety of relational exchanges. It is the dynamics between stakeholders (human agency and animal behaviour), ecosystem (the specifics of the environment) and nature (extreme physical phenomena) that determine the increasing complexity of these events. Flooding is not a recent hazard in the Philippines but one that has occurred throughout the recorded history of the archipelago: it is the result of the low-lying


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nature of much of the terrain and the frequency of typhoons. These typhoons do not necessarily constitute hazards as such and are, in fact, responsible for a significant percentage of the annual rainfall that makes the islands so fertile and thus ideal for agriculture. This fertility, in turn, encourages or at least permits demographic growth and the location of people in large cities such as Metro Manila. The demands of this steadily expanding urban population for basic amenities such as water, together with the nature of modern development, generate environmental problems like accelerated subsidence and garbage disposal that, in conjunction with the torrential rainfall associated with tropical storms, aggravates the incidence and severity of flooding in the metropolitan area. The concentration of employment, educational and health among other opportunities in the ‘big city’ only spurs more rural-to-urban migration, creates shortages of suitable residential land and encourages the occupation of areas more prone to flooding or that have important drainage functions. The actions of governments and the technological solutions they mainly favour have only limited outcomes and may actually aggravate conditions usually to the disadvantage of the most vulnerable poor, whether urban or rural. The construction of vulnerability to flood in Metro Manila, therefore, clearly shows how societies and destructive agents are very much mutually constituted and embedded in natural and social systems as unfolding processes over time.

Notes 1. Kelvin Rodolfo claims that the crater was deliberately breached with high explosives by a cartel of miners, local government and military personnel seeking treasure in the lake and that the number of casualties was much higher (2003). 2. The withdrawal of groundwater greatly accelerates the compaction of delta sediment. When water is withdrawn faster than it can be replenished, grains of sand and gravel that constitute an aquifer begin to draw moisture from the surrounding layers of clay. As both layers begin to settle and lose volume, the land surface above them subsides. 3. Shanty dwellers must also rely on shallow wells for their water needs and so further contribute to the problem of subsidence and flooding in yet another way. 4. A Metro Manila Flood Control and Drainage Council was establishment by PD 18 on 7 October 1972 that among other powers was authorised to collect an Adjustment Tax of P0.25 levied on all film tickets.

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