Expert cites measures to mitigate flooding in Cagayan

FILE: Department of Science and Technology (DOST) Undersecretary Renato U. Solidum at the Philippine Institute of Volcanology and Seismology (Phivolcs) Auditorium in Quezon City on Tuesday (Nov. 5, 2019). (PNA photo by Oliver Marquez)

MANILA – Residents and local government units were surprised by the unprecedented floods that ravaged communities in Cagayan Valley, which was a result of too much rainfall from series of typhoons and the release of water from Magat Dam.

What can the communities do to prevent this in the future?

In an interview with the Philippine News Agency (PNA) on Sunday, Department of Science and Technology (DOST) Undersecretary Renato Solidum Jr.

said Cagayan Valley naturally has a lower topography compared to the mountains surrounding it.

“The rainwater coming from those mountains goes down and goes to Cagayan River, which also causes flood during heavy rainfall. The natural flow of the river, and cutting of trees also contribute to flooding,” he pointed out.

The spilling operations in Magat Dam would affect the following areas: San Mateo, Cabatuan, Luna, Reina Mercedes, Naguilian, Gamu, Ilagan City, Tumauini, Delfin Albano, Santo Tomas, Santa Maria, San Pablo, and Cabagan in Isabela; Aurora province; Tuguegarao City, Enrile, Solana, Iguig, Amulung, Alcala, Gattaran, Lasam, Lal-lo, Camalaniugan, and Aparri in Cagayan.

“Flooding has reached Aparri, Cagayan, as this is the exit point of Cagayan River,” according to Solidum.

Reforestation

Solidum said reforestation in mountains is vital to prevent another disastrous scenario from happening in the future.

“This would slow down the rainwater from going from mountains to the river,” he said.

Another suggestion was to construct a temporary embankment, so that the water would go here.

Dredging the Cagayan River is also necessary since this is already shallow, he added.

The widespread flooding in Isabela and Cagayan would greatly affect farmers, as well as the other stakeholders in the agriculture sector, he said.

Kaliwa Dam

Is there a need to construct the Kaliwa Dam?

Solidum said while this can still be continued saying this is needed to reduce the water shortage during dry season, effective management is crucial.

“Efficient management is necessary, so that this would not cause massive flooding,” he said.

Solidum said flood maps (floods related to Typhoon Ulysses and the Magat Dam water release) were already uploaded in the Hazard Hunter app.

This DOST-managed app that can be accessed through a computer or mobile phone, helps people know if their location is at risk for volcanic eruptions, tsunamis, and other hazards.

The flood impact maps can now be accessed via hazardhunter.georisk.gov.ph.

The maps show satellite image interpretations using artificial intelligence (AI).

“Using AI, the DOST-ASTI (Advanced Science and Technology Institute) interprets whenever there is a new satellite image. Then this would be updated in the Hazard Hunter,” Solidum said.

He clarified that the flood maps are different from the hazard maps, as the flood maps show “what happened or is happening”.

‘Communities were informed’

The National Irrigation Administration (NIA) posted on its website on Sunday that the NIA-Magat River Integrated Irrigation System has advised residents of Isabela and Cagayan about the water release from Magat Dam on Nov. 9.

“NIA-MARIIS officials have warned residents living near low-lying areas, particularly those adjacent to and along the Magat River and Cagayan River to move to higher and safer places as the dam continues to release water starting November 9,” it said.

NIA is in charge of the irrigation development and management.

NIA’s claim was supported by a state hydrologist in a radio interview on Sunday.

“Yung mga local talagang alam nila, yung binibigyan nila ng abiso, pinapasok naman namin sa website namin, sa Facebook, Twitter. Lahat ginagawa naman ng paraan para makarating sa tao (The locals are aware. Those who were provided with the advisory, we upload advisory in our Facebook and Twitter accounts. Everyone does its part to inform the public),” Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) hydrologist Edgar dela Cruz said over DZBB.

In NIA-MARIIS’ Facebook page last Nov. 9, it said that the advisory was also sent to the governor, the Office of Civil Defense (OCD) and PAGASA-Tuguegarao.

Letters addressed to PAGASA-Tuguegarao City, Cagayan Governor Manuel Mamba, Isabela Governor Rodolfo Albano III, and OCD-Region 2, were sent earlier to ask for their assistance “to ensure the safety of life and properties of residents near Magat River”.

Dela Cruz also mentioned that eight to 10 hours prior to a dam’s water release, mobile cars went around areas to provide announcements.

The heavy downpour from Typhoon Ulysses caused the water level of Magat Dam to reach beyond normal.