What causes severe flooding in Cagayan province?

Jaehwa Bernardo, ABS-CBN News

Posted at Nov 15 2020 01:43 PM

What causes severe flooding in Cagayan province? 1
Scenes from Tuguegarao along the city’s main road towards the capitol as the area experiences floods in the wake of rains brought by Typhoon Ulysses on November14, 2020. Chiara Zambrano, ABS-CBN News

MANILA — A local official and a scientist have offered explanations as to why Cagayan province frequently experiences intense flooding.

In a Facebook post, Fernando Siringan, former director of the University of the Philippines Marine Science Institute (UP-MSI), said the region serves as a catch basin of water from surrounding mountain ranges.

Both water and sediments from the mountains cause the rivers to overflow, prompting floods, Siringan said on Saturday as flooding inundated large parts of Cagayan Valley in the wake of Typhoon Ulysses (international name: Vamco).

Local officials had earlier attributed the severe flooding to water coming from surrounding areas as well as water released from the Magat Dam located in Isabela.

"Sa pagbaba ng maraming tubig kasama ang sediments mula sa mga kabundukan, umaapaw ang mga ilog at maaaring mabilis na magpalit ng posisyon. Paghupa ng baha ay may mga naiiwang putik, buhangin at kaunting graba," Siringan said.

The Cagayan River also becomes narrow in the portion of Sicalao Ridge because of old and deformed sedimentary rocks.

This narrow portion of the river starts at Barangay Tupang in Alcala, Cagayan and ends at Magapit in Lal-lo town, according to Siringan.

"Ang mahabang makipot na channel ng Cagayan River ay nakapagpapabagal sa pagdaloy ng tubig papunta sa bukana ng ilog sa Aparri. Dahil bumagal ang daloy ng ilog, naiipon ang tubig sa kapatagan, umaapaw sa channel at nagbabaha," he explained.

A 1987 study from the Japan International Cooperation Agency (JICA) on the flooding in Cagayan Valley, Siringan said, recommended the widening of the narrow portion of the Cagayan River from Alcala to Lal-lo.

But the scientist noted that the recommendation had yet to be fulfilled until now.

Alcala Mayor Cristina Antonio, in a Facebook post on Sunday, also cited the 1987 JICA report and lamented how the recommendation had "not been acted upon."

Earlier this year, Antonio had enlisted the help of Siringan and UP geologist Keanu Jershon Sarmiento to conduct a study on the flood and riverbank erosion on the Cagayan and Pared Rivers in Alcala.

Antonio also cited illegal logging and agriculture in slopes and mountains as causes of flooding.

"Mountains, slopes and watersheds in the whole Cagayan Valley have been stripped of native trees that hold soil and regulate water release," she said.

"Trees are cut down and forests threatened not only by illegal logging but by agriculture in slopes and mountains, particularly yellow corn farming and the use of herbicide that kills all vegetation and weakens the soil," she said.

Through the Siringan and Sarmiento study, Antonio began implementing changes in Alcala, including convincing farmers to abandon yellow corn farming and shift to agroforestry.

Alcala residents have also started planting trees around irrigation dam watershed areas, Antonio said.

The local chief executive said she engaged the 25 barangays to "plant tiny, dense, native forests in their communities, using the Miyawaki method," a technique pioneered by a Japanese botanist to help build dense forests.

"We are set to plant native forest and flowering trees on all Alcala roadsides that span around 120 kilometers," she said.

Antonio said severe flooding experienced in the Cagayan Valley in the past days could not solely be blamed to "Magat Dam protocols."

"It’s about us, it’s the way we live — as if we are apart from nature, as if what we do does not come back to us. It’s us — how we have cut our trees and destroyed our forests, our soil and groundwater, how we have eaten up the land with farms and buildings," she said.

Antonio said the solution to the flooding problem in the region should be "a combination of interventions that should be anchored on science" and drawn from scientists who have studied the Cagayan Valley.

"I hope our leaders, and all of us, will help to save Alcala, and the whole Cagayan Valley. Please, let us listen to our scientists," she added.


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