A look back at Cagayan flooding

MANILA, Philippines — If there’s a word to describe the recent flooding that happened in Cagayan due to Typhoon Ulysses, it would be “surprising,” at least according to Governor Manuel Mamba.

When parts of the province of Cagayan was hit by flooding during the fourth quarter of 2019, Mamba said the water level at the Cagayan River only reached 11 meters. But during the height of Typhoon Ulysses, the governor said the water level rose to 13 meters.

The water level was so high that Tuguegarao residents reported that there was flooding in areas for the first time in 45 years, said Mamba.

The flooding in Cagayan left many residents stuck on their roofs, waiting to be rescued. Those who were not able to get to safety as the water quickly rose perished.

Eyes are on the National Irrigation Administration (NIA). Local government officials see the discharge of water from Magat Dam, one of the largest dams in the Philippines along the Magat River, as one of the biggest contributors to the flooding.

Advisories were released

Wilfredo Gloria, department manager of the NIA Magat River Integrated Irrigation System, said that under their protocols, water has to be released from dams two to three days before the expected impact of the storm.

And that was what they did, Gloria told INQUIRER.net in a Zoom interview.

According to Gloria, advisories were sent to the Office of Civil Defense (OCD) and municipal and city government offices six hours before opening the floodgates in Magat Dam.

Gloria said notices were sent regarding the pre-release of water in Magat Dam on November 9 when two gates were opened. This was three days before the expected arrival of Typhoon Ulysses in Northern Luzon on November 12.

“It was sent through emails, text messaging, tsaka yung mga hard copies then sinabayan natin ng pagbibigay din ng notices sa ating mga radio stations kasi alam naman natin na malawak ang sakop ng ating mga radio stations,” Gloria said.

Gloria added there were also flood warning systems along the Magat River.

“Ito ‘yung may public address system na sinasabayan din ng siren na ibig sabihin, ‘yung mag-antabay ‘yung ating mga kababayan na nasa along the riverbank of Magat River, sa loob ng anim na oras ay dadaloy na yung tubig na pakakawalan ng Magat Dam. May sirena, may siren,” he explained.

(These are public address systems with sirens, which means that those along the riverbanks of Magat River should be on alert because there would be water discharged from the Magat Dam in six hours. There are sirens.)

But on the night of November 11, Gloria said the Cagayan Valley started to feel the impact of Typhoon Ulysses as heavier rainfall poured in the area.

This prompted the NIA to open more gates on November 12 as water flow in Magat Dam increased, said Gloria. However, the NIA official clarified that the seven floodgates of the dam were not opened simultaneously.

“For every additional opening ng ating gates, may corresponding notices din tayo through texting, so ‘yun ang ating mga proseso,” he said.

(For every additional opening of gates, there is a corresponding notice, that’s our process.)

“Then ‘yung sa notice of pre-release natin, it was sent through emails, all means na makarating sa ating mga kababayan ‘yung impormasyon na ‘yun,” he added.

(Then for notice of pre-release, it was sent through emails and all means that would reach our residents.)

Message unclear

But if it were up to Mamba, the likely impact of the dam water discharge, as well as the gravity of flooding that it may cause, was not adequately conveyed and explained.

“Sa amin, we don’t know the extent of the effect on the flooding itself. Kahit na sabihin mo sa aming 6,000 [cubic meters per second of water], kahit sabihin mo sa aming apat na swimming pool per second ang mailalabas niya,” Mamba told INQUIRER.net in a phone interview.

(We don’t know the extent of the effect of the flooding itself. Even if they tell us to expect 6,000 cubic meters per second of water, even if they tell us it’s equivalent to four swimming pools, we don’t know that.)

“’Di naman [kami] sinabihan na magpa-evacuate na kayo dahil mag-release kami ng ganito, ganito kasi ang mangyayari, they do not even tell us dahil hindi nila alam kung gaano kalalim. ‘Di nila alam kung anong epekto ng binibitawan nila,” he added.

(We were not told to evacuate because they will release this amount of water, because this will happen, they did not even tell us because they did not know how deep the flooding would be. They don’t know the effect of what they would release.)

They did not expect the “gravity and enormity” of the water that inundated vast parts of Cagayan even if the government had prepared even before the storm’s expected impact on the province.

“Last year kasi, the last quarter of last year, almost three months kaming nagre-relief, nagre-rescue dahil sa flooding. Talagang grabe yung flooding dito for the last three months of last year so we expected this to happen again so that’s why noong darating yung Ulysses, although wala kaming typhoon signals, talagang nag-prepare din kami,” Mamba said.

“We forewarned people na baka maulit yung last year. We had a pre-disaster coordination, we had pre-emptive evacuation, even forced evacuation in certain areas. And then we had a meeting the morning before yung flood ay nag-start,” the governor added.

Mamba said there were “unprecedented” landslides in parts of northern Cagayan due to the amount of rainfall recorded in the province days even days before Typhoon Ulysses.

“Super saturated na ang lupa namin dito. For so many days na kasi or even ay panay ulan. Kaya nung dumating din yung tubig ng Ulysses, dagdag na lang yun,” Mamba said.

Not just Ulysses

According to Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) weather forecaster Ariel Rojas, several factors can be considered for Cagayan flooding.

For one, Rojas said eight storms hit the country during October and the first half of November.

“Naka-walong bagyo na tayo na dumadaan so itong mga systems na ito ay nagpaulan na, hindi naman siguro ganoon ka-significant ang impact sa atin but enough yung kanyang ulan para mag-saturate ng lupa at mabawasan significantly ang absorption capacity ng lupa,” Rojas told INQUIRER.net in a Zoom interview.

(We had eight storms and these brought rainfall. While their effect might not have been that significant, it is enough to saturate the soil and reduce the soil’s absorption capacity.)

“So, yung runoff diretso sa ilog, hindi na siya naa-absorb ng lupa kaya dire-diretso na ‘yan sa ilog,” he added.

(So the runoff goes straight to the rivers since the soil can no longer absorb them.)

Aside from the previous storms that ravaged the country, Rojas said the cold front’s tail-end was also bringing rains to the Cagayan area even before Typhoon Ulysses impacted the province.

“[May] confluence ng several factors—at hindi lang ni Ulysses. May other existing weather systems before dumating si Ulysses na nagpapaulan na dyan sa northern part ng Cagayan and sa may Cordillera,” Rojas explained.

(There are several factors and not just Ulysses. There are other existing weather systems before Ulysses came that brought rain in the northern part of Cagayan and Cordillera.)

“’Yung tail-end ng cold front ay ilang araw nagpapaulan at malalakas ang ulan na dala ng tail end ng cold front at ilang beses din naglabas ang Northern Luzon office ng Pagasa ng heavy rainfall warning dyan sa may Cagayan Valley area dahil sa malalakas na ulan dulot ng tailend,” he added.

(The tail-end of the cold front had been bringing rains for several days and the Northern Luzon office of Pagasa issued a heavy rainfall warning in the Cagayan Valley area due to the rains brought by the tail-end.)

Looking at Rojas’s data on the amount of rainfall recorded at their station in Aparri town in Cagayan, it was clear that there was an increase in rainfall on November 12, the day when seven floodgates of the Magat Dam were opened.

November 8 – 128.7 millimeters (mm) of rain over a 24 hour period

November 9 – 83 mm of rain over a 24 hour period

November 10 – 61.1 mm of rain over a 24 hour period

November 11 – 22.6 mm of rain over a 24 hour period

November 12 – 209 mm of rain over a 24 hour period

It was also on November 12 when the effects of Typhoon Ulysses and the cold front’s tail-end were battering the Cagayan Valley.

“So dalawang weather systems ‘yung nagpapaulan doon at nagtulak nga para itong Magat Dam ay magbukas ng gates,” Rojas said.

(So two weather systems brought rain and led to the decision for Magat Dam to open gates.)

Who’s to blame?

Gloria said the blame should not be only on NIA, pointing out that the Cagayan River has 20 tributaries and the Magat River is just one of them.

“Dahil sa malawakang pag-ulan na dulot nitong Bagyong Ulysses, halos lahat nitong 20, including Magat, ay nag-contribute ng pagbaha…. ‘Pag nagkasabay-sabay itong 20 tributary rivers na nag-contribute ng malaking tubig ay talagang malawakang pagbaha,” he insisted.

(Because of the rainfall brought by Typhoon Ulysses, almost all of the 20 tributaries, including Magat, contributed to the flooding… If these 20 tributary rivers would bring large amounts of water simultaneously, there will really be flooding.)

He further emphasized that soil in Cagayan Valley is already saturated with continuous rain over the past few days before the flooding.

“If we will hold the water coming in, it will compromise—mao-overload ang Magat Dam… at mas lalong grabe ang magiging epekto niyan which would result to dam break, the worst is to collapse,” Gloria said.

(If we hold the water coming in, Magat Dam will be overloaded and the effect will be worse, like dam break, or worst, it will collapse.) [ac]