A season of floods

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Saturday, August 31, 2013

THE scene was straight out from “The Impossible” movie – except that it didn’t happen in Thailand but in the Philippines, particularly Compostela Valley, during the time when Typhoon Pablo struck the province.

As onrushing water held them captive, Rogelio Saging held tight his three young children with his eldest son Rudyard close behind. His wife Violeta was also trailing them. But the current was so strong; the water was loaded with silt, gravel, boulders and clumps of fallen trees that they almost lost their hope of surviving.

Then, the unthinkable happened. The parents saw how a fallen coconut tree hit the head of their third year high school son and carried him away from their grasp. All was chaotic after that; they, too, were swept away by the strong flood.

At around 2 in the afternoon, it was a joyful and tearful reunion as the parents had found all their 4 children – except for Rudyard, who was in a very critical condition. Rescuers had found him barely clinging on to his life. Rogelio had only a few precious moments to talk with his son before his torn and mangled body finally gave up.

Scenario like this will again be common reality in various parts of the country as rainy season is here again. Along with the rain are devastating typhoons and ensuing floods. So far, only 5 typhoons have entered the Philippine Area of Responsibility (PAR) this year. Typhoon Emong is the most recent.

This means there are 15 more typhoons coming. “Each year, about 20 tropical cyclones enter our country,” says Rene Paciente, chief of the weather forecasting and warming system of the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa).

Fortunately, only 6 to 9 of these tropical cyclones make landfall. In the Filipino dialect, tropical cyclones are called “bagyo,” a word which came after a 1911 storm in the city of Baguio, which had a record rainfall of 46 inches within a 24-hour period.

Tropical cyclones are low pressure systems characterized by relatively low atmospheric pressure at the center with very strong winds blowing counterclock wise (in the northern hemisphere) towards and around the center.

Depending on the intensity and strength of the winds that they bring, tropical cyclones are classified as tropical depression, tropical storm, and typhoon. A tropical depression has maximum winds from 35 kilometers per hour (kph) up to 63 kph. A tropical storm has winds moving anywhere from 64 kph to 117 kph. When it exceeds 117 kph, typhoon ensues.

When there is typhoon, there is always flood. “The back-to-back typhoons left waters raging across the Philippines” was how the United Press International (UPI) described of the inundation that came in the wake of typhoons Ketsana and Parma in 2009.

“Scores of people have died as heavy rains caused flooding and landslides in the Philippines,” UPI reported. “Ketsana made landfall at the Philippines September 26, killing about 300 people and destroyed thousands of homes. Parma reached the country about a week later with about 120 deaths associated with the storm.”

In 1991, Ormoc City in Leyte was once devastated by a colossal flood, killing about 8,000 people, wherein half of the victims’ bodies were never recovered. Walls of mud and water emanating from mountain washed away shanties and swept people into the sea, a tragedy that brought lamentations all over the place and in the whole Philippines.

A flood is an overflow of water that submerges land which is normally dry. “Floods are due to the complex combination of weather, climatic and human activities,” notes a briefing paper circulated by Pagasa during a seminar workshop convened by the Department of Science and Technology in Davao City recently. “Most floods occur as a result of moderate-to-large-scale rainfall events.”

Among flood’s natural causes are intense and prolonged rainfall, storm surge, and high tide. “Weather disturbances such as low pressure areas, tropical cyclones, intertropical convergence zone (ITCZ), monsoons and cold fronts could lead to flooding,” the Pagasa briefing paper states.

A low-pressure area is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere.

Known by sailors as the doldrums, ITCZ is the area encircling the earth near the equator where the northeast and southeast trade winds come together.

Traditionally, monsoon is defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. Generally, the term monsoon is used to refer to the rainy phase of a seasonally-changing pattern.

A cold front is defined as the leading edge of a cooler mass of air, replacing (at ground level) a warmer mass of air, which lies within a fairly sharp surface trough of low pressure.

All these weather disturbances bring a lot of water causing flooding in affected areas. The same thing happens when there is a storm surge, “a rise of seawater above the normal level on the coast generated by the action of the wind and atmospheric pressure, associated with the occurrence of a tropical cyclone.”

According to a Pagasa briefing paper, a storm surge can inundate low-lying coastal communities as the level of the ocean is raised by several feet. This happened in Metro Manila in 2011, when large waves that hammered the coastline of Manila Bay caused flash floods in areas. The huge waves caused by the storm surge battered the bay's seawall, causing portions of the wall to collapse.

Likewise, high tide that coincides with high stream flows can aggravate flooding near the coasts. Early this year, torrential rains inundated many barangays in Davao City as Bankerohan River overflowed and submerged houses along river banks displacing hundreds of residents.

There are several human activities that can alter the natural ground cover of a river basin thus increasing the size and frequency of floods.

For instance, encroachment by informal settlers of the waterways can obstruct the normal flow of floodwaters. In addition, indiscriminate dumping of garbage can also cause clogging of waterways.

Increased urbanization and coastal development can increase the impermeable surfaces due to concreted roads and losses its ability to absorb flood waters that may result to flash flooding.

Deforestation and blasting likewise contribute. Deforestation reduces the infiltration capacity and speed of the flood flows. Blasting, on the other hand, causes landslides in the slopes of hills and mountains and may result in unintentional damming of rivers and streams.

Failure of levees and dams can create the worst flood events by releasing large quantities of water, according to the PAGASA briefing paper.

The briefing paper also shared some safety tips before flooding, during the flood, and after the flood. It said that when warned of flood, the following should be done. Securely anchor weak houses. Drinking waters must be stored in containers as water service may be interrupted.

Household belongings should be moved to upper levels while livestock are bought to higher grounds.

Should there is an advice of an evacuation, it must be followed. “Do not panic, move to a safe area before access is cut-off by floodwaters,” it said. “Turn off main electricity switch and gas valve, and lock your house before evacuating.”

Before flooding occurs, keep these in mind: Keep informed of the daily weather conditions and forecast from the weather bureau. Be aware how often your location is likely to be flooded and to what extent. Know the flood warning system and evacuation plan of your community and make sure your family knows them. Designate an evacuation area for the family and livestock and assign family members specific instructions and responsibilities according to an evacuation plan. Keep a stock of food which requires no or little cooking and refrigeration, good at least for 3 days. Keep a transistorized radio and flashlight with spare batteries, emergency cooking equipment, candles, matches, and first aid kid hand in case of emergency.

During the flood, stay indoors. Do not attempt to cross rivers with flowing streams where water is above the knee. Beware of water-covered roads and bridges. Do not go swimming or boating in swollen rivers. Beware of contaminated food and water.

After the flood, here are the things you need to do: Reenter the house with caution using flashlights. Flammables and dangerous animals like snakes may be inside. Be alert for fire hazards like broken electric wires. Do not eat food and drink water until they have been checked for flood water contamination.

Report broken utility lines (electricity, water, gas, and telephone) to appropriate agencies or authorities. Do not turn on the main switch or use appliances and other equipment until they have been checked by competent electrician. Do not go “sight-seeing” in disaster area. Your presence might hamper rescue and other emergency operations.

It’s rainy season again – and 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.”

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