Geological Factors that contributed to the destructive nature of Typhhon Quinta that hit Iloilo and Capiz last month and measure to address these problems: A Reaction Paper With 52,172 families (251,152 persons) affected, many Filipinos celebrated their recent holiday vacations with grief as Typhoon Quinta hit the Phlippines destroying millions of properties and owing 15 people their lives. Millions of pesos worth of agricultural crops and infrastructures were also damaged in 544 barangays of the 40 municipalities and four component cities of Negros Occidental, Iloilo, Capiz, and Aklan. Typhoon Quinta brought more devastation to many towns in Iloilo and Capiz compared to Typhoon Frank as far as flood water is concerned. Waters from Suague River which originates from the mountains of Janiuay and Jalaur River in Calinog engulfed towns along its way towards the sea especially after combining as one river in the Municipality of Mina even though Tigum and Aganan Rivers did not overflow its banks.
Towns of Pototan, Barotac Nuevo, Dingle, Dueñas, Dumangas, and Zarraga located downstream were devastated as the waters of the combined rivers made flood water levels relatively higher than that of Typhoon Frank’s. The natural recipe for flooding is that a day before a heavy downpour is hours of light rain as a forward effect of an incoming typhoon which will saturate the upper ground portion. When the typhoon comes in bringing with it heavy rains at 20 mm/hr., the ground cannot accept anymore the additional heavy downpour. So instead of a 9 percent penetration with 91 percent run off of overload flow, it will now be 1 percent penetration with 99 percent of the heavy rain as storm water runs off, hence a heavy surge of water across the land which we experience as flood. Now what hit most towns north of Pavia appears to be heavy rains of about 15 to 20 mm/hour.
Trees play a very vital role together with watersheds in relation to flooding. The leaves of trees act as cushion to rain so that it will fall slowly and that by falling slowly, rain will gently reach the ground surface preventing compaction and therefore allowing more time to infiltrate the ground to be part of the underground regime. A study conducted for the Aganan and Tigum watersheds made by a hydro-geology consulting firm, Sweco, hired by MWID in 1997 showed that a hundred years ago, rain infiltration was 15 percent but at the time of study, it declined to only 9 percent. This was mainly because of the reduced forest cover and the increase of impermeable surfaces such as roads, basketball courts, houses, and other structures which prevent the effective infiltration of rain into the ground. In addition, a watershed is a land area where rain falls and is drained by a river system, hence the Suague watershed is that mountain portion in Janiuay where rainfall is drained by the Suague River which passes the town proper before merging with Jalaur River which also drains a separate mountainous area.
The best watershed in the country would be the rainforests found only in remote mountains in Mindanao, however, such are already fast vanishing. These are virgin forests with trees of hundreds or thousands of years old with thick undergrowth of vines and shrubs. The top soil is composed of thick decayed vegetation that if one jumps on it, the entire top soil up to 20 meters away vibrates and behave like a sponge and therefore a very good absorbent of rainfall. For us to restore our watersheds to rainforest condition there should be a strict implementation of the rule of absence of human activities because the mere planting of trees already seemed to be not enough. Raising cows and carabaos in the Tigum watershed must be prohibited so that the ground will not be compacted and people will not frequent the mountains.
The rise of flood waters in Typhoon Quinta was so fast that in just a matter of minutes, it reached 5 to 8 feet high. This is basically because our rainforests are in a bad condition. The condition of our watersheds in the mountain determines the timing of the release of storm water towards the plain of lowland where population centers are located. If our mountains are fully-covered with trees and there is undergrowth of vines and shrubs plus an increase in rain penetration, then the flow of water towards the rivers will be gradual instead of a surge thus preventing a destructive flood. With increased globalization and modernization, our economy cannot afford to be left out by the rest of the world. Of course, we must also keep up with technological innovations. However, we must not forget our responsibilities in protecting our environment.
We must not put into risk the future of the next generations that would inhabit the world but instead, we must take into consideration the concept of sustainable development. Our government should pass and strictly enforce laws that maintain hydro-geological conditions of our rainforests before and after any developments in infrastructures. Also, we citizens must be cooperative in these efforts of the government and must follow these rules. Typhoon Quinta highlighted the importance of disaster preparedness.
We must always keep in mind what National Disaster Risk Reduction and Management Administrator Usec. Benito Ramos said: “the typhoon should teach us to be always prepared and it is a lesson for all of us that whenever there is a weather disturbance anywhere in the Philippines, there is no place that will not be affected.” The bottomline is, what we need is discipline and a sense of responsibility. Whatever happens in this world, we, its inhabitants, always have something to do with it. If only we’ll be disciplined enough to impose and follow rules, and be responsible to take care of this only place where we can live, then we won’t be facing such disasters and surely, we’ll live in this world safe and sound.
Courtney from Study Moose
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