By Henrylito D. Tacio
Three’s a company, so goes a popular saying. So is disaster. In the Philippines, disaster arrives together in three forms: typhoon, rain, and flood.
Among the three disasters, flood tops. Rain happens all the time. Of the 20 tropical cyclones that hit the country every year, only 6-9 typhoons make landfall, according to the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA).
But flood is a different story. Once it happens, no one can stop it. Flood wreaks havoc not only to the surrounding that it passes through but also destroys home, buildings, bridges, and even takes lives.
The Department of Science and Technology (DOST) classified flood under the so-called hydrometeorological hazard that also include tropical cyclone, storm surge and rain-induced landslide.
Volcanic eruption, landslide, earthquake and its related hazards (ground shaking, liquefaction, ground rupture, tsunami and landslide) are categorized under the geological hazard.
Flood — which comes from the Old English flod, a word common to Germanic languages — happens “when water from streams, rivers and other bodies of water overflow to low-lying areas due to heavy and prolonged rainfall and when rain waters are not drained rapidly due to inadequate or defective system or when coastal water rises due to high tide or storm surge.”
Rosalie C. Pagulayan, weather specialist II of PAGASA, said typhoons generally bring floods. But typhoons are the not the only flood initiator. “Floods are due to the complex combination of weather, climatic and human activities. Most floods occur as a result of moderate-to-large-scale rainfall events,” she explained.
The Philippines, given the location and the topography of the country, experiences four other weather-causing phenomena which can bring floods. These are: thunderstorms, cold front, monsoons, and intertropical convergence zone (ITCZ). The weather bureau gives the following insights on the four phenomena:
Thunderstorms, called local storms, occur when towering cumulus clouds reach a height where the temperature is well below the freezing point. Among the associated hazards are heavy rain (which may cause flashflood) and lightning (which may cause death, burns or fire).
Cold front is formed when cold air moves over areas of warm air. Since cold air is heavier than warm air, the warm air is pushed aloft by the cold air giving rise to widespread cloudiness. The cold front affects the eastern part of the country from November to late April or early May.
There are two types of monsoon: Southwest and Northeast. In the former, the Asiatic continent becomes warmer than the surrounding seas and a low-pressure cell develops over the continent. This causes a flow of moist southwest wind over the Philippine area. At times, when this southwest flow becomes thick in depth, it persists for a long period causing continuous rains which may last for weeks during the months of June to September.
The Southwest monsoon is responsible for the great portion of rainfall during the country’s wet season. Known by sailors as the doldrums, the ITCZ is an area where the northern hemisphere trades meet the southern hemisphere trades. According to the weather bureau, ITCZ is characterized by towering clouds of cumulonimbus clouds accompanied with showers of widespread thunderstorms.
“The axis of convergence, which is usually oriented in an east to west direction, does not remain stationery at the equator but migrates north or south of the equator,” a briefing paper from PAGASA explains. In the Philippines, it oscillates during the months of May to October.
All these weather disturbances bring a lot of water causing flooding in affected areas. But there are also human activities that cause floods, according to the DOST-published book, Reference for Emergency and Disaster. These are: increased urbanization and coastal development; indiscriminate dumping of garbage in waterways, canals and drainage systems; informal settlers constructing illegal structures along and on top of waterways; deforestation; blasting that causes landslides and damming of rivers; and failure of levees.
A really big flood can cause billions of pesos in damage to agriculture, infrastructure, loss of productivity in industry and commerce, not to mention loss of human lives. Congested urban centers like Metro Manila could stand still for days.
“With too much rain and floods, agriculture production especially in flood-prone areas will be adversely affected with physical and economic losses,” pointed out Dr. Rafael D. Guerrero, who is with the National Academy of Science and Technology. “Floods will wash away crops, hasten soil erosion and increase crop spoilage due to poor storage and distribution problems.”
The Department of Health said floods will accelerate food-borne and water-borne diseases. “Flooding can contaminate the public water through the disruption of water purification and sewage disposal systems, rupture of underground pipelines and storage tanks,” the health department said.
Using contaminated water can cause a wide spectrum of illnesses, among them: acute gastroenteritis, dysentery, typhoid fever, cholera, and hepatitis A. “Foods that may have been in contact with contaminated floodwater should not be eaten,” the health department advised.
In addition, there is an increase of leptospirosis cases after heavy rains or flooding incidents. This livestock disease transmissible to many may be acquired through wading in water contaminated with urine of infected animal.
Mosquito-borne diseases like dengue fever and malaria also rise with the increase in mosquito breeding grounds. And with the cold weather also come airborne diseases like influenza, which spread fast in congested areas such as Davao City’s inner cities.
As floods are common throughout the country, the weather bureau has launched the Flood Early Warning System (FEWS) capacities. It has five basic elements: prediction, detection, communication, decision-making, and mobilization.
“In any disaster of given magnitude, the first line of defense is still awareness of the communities at risk,” reminded Pagulayan.
It’s rainy season once more. As another saying goes, forearmed is forewarned. Listen to the woes of one flood victim: “The downpour of rain is unprecedented. The rain came without much warning. When we woke up in the morning, there was intermittent heavy rain and I thought that it is seasonal – indeed the rainfall throughout this year has been quite heavy, unlike during the last three years. The rain water reached two feet on the main streets. I couldn’t drive, there was water everywhere.”
Now, for our weather forecast!