|A flood affected resident looks from a window of a school building serving as an evacuation center in Marikina town, suburban Manila on Aug. 9. (AFP-Yonhap News)|
There was no storm over Metro Manila last week. But why was there so much rain? Why was the flooding so severe?
Those were the questions asked by Jose Ma. Lorenzo Tan, CEO of the environmental group Worldwide Fund for Nature (WWF)-Philippines.
Filipinos, not the monsoon rains, are to blame for the deluge that paralyzed the metropolitan area of 14 million residents last week, according to Tan.
In an analysis, Tan said the latest disaster to hit the Philippines was a result of an unfettered and mindless march to urbanization that had replaced soils and trees, which could absorb the rains and reduce flooding, with concrete jungles.
One classic example is Quezon Memorial Circle. What used to be a vast green space has been transformed into a giant “tiangge” (market) and “carinderia” (eatery).
Construction by the Quezon City government of buildings continues unabated in the park, where grass is fast disappearing just a spitting distance from cavernous shopping malls.
Now, during downpours, the areas surrounding the park are flooded and traffic is snarled.
The buildings, the concrete and the asphalt have trapped and increased the temperature in the metropolis, making it an “urban heat island,” or UHI, Tan said.
Pollutants from buses, cars and factories also contribute to the warming of the city as they block the heat rising to the atmosphere.
Because of all these urban development and human activities, there is more heat that lingers on the ground that interacts with the weather, Tan said.
In the case of Metro Manila this time of the year, the UHI worsens the southwest monsoon, the dominant weather system.
Along with the Philippines’ location on the typhoon path and climate change, UHI is the third factor for the unusually heavy and relentless rains that crippled the capital last week, Tan said.
“Urban heat islands” are aggravations that intensify the water cycle. They are “magnets” that draw in and enhance weather systems such as cyclones, low-pressure areas and the monsoon.
“In some cases, they have been known to spawn local tornadoes. We saw that right in Quezon City just last year, where seven barangays (villages) were reported to have been badly affected,” Tan said.
Record rain since ‘Ondoy’
The monsoon drenching last week produced the highest volume of rainfall seen in the city since the record-breaking downpours brought by Tropical Storm “Ondoy” in 2009, claiming close to a hundred lives in the rampaging flood tides.
The amount of rain from August 6 to 8 reached 1,007 millimeters. The weather bureau’s projected accumulated rainfall for August was only 540 millimeters.
The torrential rains that enveloped the city forced 2 million people in Metro Manila to evacuate to safety and crippled 80 per cent of the city.
Tan’s statement aligns with the findings of a researcher at the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa).
The UHI effect distorts the heat balance, wind circulation and precipitation in the city, according to Nivagine Nievares, a weather specialist at the Pagasa.
Nievares’s 2010 masteral thesis showed that rapid development in the city had made Manila hotter compared to the rural regions around it.
Metro Manila’s buildings, the roads and the pollutants in the air absorb and trap the heat from the sun, pushing the mercury higher especially during summer, Nievares said.
Solar heat flux
According to Nievares, Metro Manila’s temperature during April is 1-2 degrees Celsius higher than in the nearby and less developed province of Bulacan.
“Later in the day, as net solar radiation increases, most of the urban surface materials absorb and store a lot of energy [and] convert most of this energy into sensible heat flux,” Nievares said. “The increase of sensible heat flux contributes to the increase of temperature over the urbanized area.”
During the dry season, the UHI phenomenon could generate oppressive heat. But at this time of the year, during the wet season, the phenomenon could help intensify monsoon downpours, she said.
Nievares noted that pollutants interact with the water molecules in the atmosphere.
“A chemical reaction takes place; the pollutants stick to the molecules of the water vapor,” she said in an interview yesterday. “This makes the raindrops bigger. This is why sometimes the rains feel heavy.”
Depending on the season, the UHI could also change the wind circulation and the patterns of cloud formation, variables that affect rain clouds and thunderstorms, she said.
Politics, poor planning
But the UHI effect could not be blamed on the vagaries of weather. Tan’s and Nievares’ findings clearly showed that rapid urbanization was the culprit for the UHI.
“The problem lies in Metro Manila’s poor planning, political gridlock, inadequate or inappropriate urban management, the inadequate implementation of zoning rules and land use plans, haphazard real estate development, among others,” Tan said.
“Like most megacities in Asia, Metro Manila has adopted the long outdated Western development model referred to as ‘the urban sprawl.’ Megacities that extensively convert porous and water-absorbent land to impervious expanses of concrete generate a tremendous amount of heat. When land conversion and real estate development are allowed to grow in a haphazard manner, it only makes things worse,” he said.
Nievares said the concrete and the asphalt that covers Metro Manila generate a lot of heat that contribute to the warming of the city. The dark color of the city’s roofs is also a problem.
Because Metro Manila residents tend to use gray or red paints on their roofs, the heat from the sun is not reflected to the atmosphere. Instead, it is absorbed on the ground.
More erratic weather
Tan warned that Metro Manila would see more extreme and erratic weather in the future, thanks to the triple whammy of the UHI effect, climate change, and the country’s position on the typhoon path.
“Historically, most typhoons entering the Philippines come from the Pacific Ocean. Over the last four years, however, we have seen extreme weather systems develop in the West Philippine Sea,” Tan said.
“Although this was not a frequently recurring situation ten or twenty years ago, the West Philippine Sea is now occasionally warm enough to be a spawning area for a phenomenon called tropical cyclo-genesis, i.e., the birth of storms. The province of Pangasinan has experienced this, first hand. With global warming, we should not be surprised if this is happening,” he added.
“Climate change changes everything. Humankind created it. The haphazardly built megacities of Asia are aggravating it. Metro Manila’s garbage mess and woefully inadequate transport system just makes it worse. We started it. We can stop it. But, let’s stop pointing fingers at the monsoon,” Tan said.
“Some of the decisions will not be easy. But we have no choice. We only have one Philippines, and one planet.”
By Kristine L. Alave
(Philippine Daily Inquirer)