Marikina River dredging helps control flood
If the impact of the recent super typhoon “Karding” showed Marikina City officials anything, it is that dredging the Marikina River is fundamental in protecting the spine of the city, according to a report by Manila Bulletin.
In an interview with Manila Bulletin, Marikina City Engineer Kennedy Sueno cited the significant changes observed in terms of flood control due to their non-stop dredging operations.
“Noong time ng Ulysses, ang daming area na inabot [ng baha]. Nitong Karding, although naka 18.4 ang aming sukat sa ilog, konti lang at ang malapit lang sa ilog ang natamaan (During typhoon Ulysses, many areas in our city were severely flooded. For Karding, only the barangays nearest to the river were affected, even though we reached 18.4 meters in our river water level),” Sueno said.
In 2009 and 2020, typhoons “Ondoy” and “Ulysses” respectively submerged a vast majority of Marikina City. The Marikina River water level reached 22 meters during Ulysses, and 23 meters during Ondoy.
Noted for its “rapid intensification,” Karding placed Metro Manila and multiple provinces under Tropical Cyclone Warning Signal (TCWS) No. 3 on Sunday, Sept. 25, coupled with a red rainfall warning alert by the National Disaster Risk Reduction and Management Council (NDRRMC).
Marikina City was among the northern metropolitan cities that were placed under TCWS No. 4 on Sunday afternoon.
“[Ngayon], hindi na umabot [ang baha] hanggang second floor. Ang pinakamalalim na naencounter namin ngayon ay hanggang hita lang (The floods did not reach the second floor. The deepest flood we encountered this time was only thigh-high),” Sueno added.
Lesser flooded areas also meant lesser and easier clearing and cleaning of affected roads and streets which, he said, were finished by Thursday, Sept. 29.
Seeing their efforts bearing fruit, the dredging of the Marikina River has been considered a fundamental part of its regular maintenance.
“Ang ilog, kapag umulan lang, matatabunan na naman ulit ang mga nadredge mo. Ang ilog na ito galing pa sa San Mateo, Montalban. May mga quarry doon sa taas. Iyon din ang tumatapon sa ilog. Kaya ‘yung dredging operation na ito, walang katapusan ito (The dredged river will pile up again and again when it rains. This river runs up to San Mateo, and Montalban in Rizal. There are quarries in those elevated places, and their debris roll down to the river. That’s why there’s no end to this dredging operation),” said Sueno.
“Nasimulan na ni Mayor Marcy iyan. Nakita naman na effective ‘yung nangyari. Tuloy-tuloy lang (Mayor Marcy started this project, and it will continue. We have seen that it is effective),” he added.
The Marikina River Restoration Project (MRRP) of the national Task Force Build Back Better (TF BBB) officially began in 2021.
It is a multi-sectoral initiative of the Department of Public Works and Highways (DPWH), the Department of Environment and Natural Resources (DENR), and the Metropolitan Manila Development Authority (MMDA), in partnership with the Japan International Cooperation Agency (JICA).
The Marikina City local government follows the MRRP and coordinates with the aforementioned agencies.
However, Sueno said they also conduct their own independent dredging operations, focusing on the parts of the river running within their area of jurisdiction.
A dredging operation can excavate an average of 2.5 to 3 meters in depth.
“Naka 52,700 cubic meters na kaming nakuha. Halos 2 kilometro na ang nadredge (We have gotten around 52,700 cubic meters [in terms of the volume of extracted materials]. We’ve already dredged around two kilometers [of the river]),”he said.
From the previous 50 to 60 meters, they are widening the river to 80 meters, in accordance with the design set by JICA.
Workers from the engineering department work from 8 a.m. to 5 p.m. everyday, manning their six dredging machines, consisting of five long-arm backhoes, and one amphibious long-arm excavator.
The amphibious excavator is the long-arm backhoe that floats on the water. It’s the primary machine that digs the river itself and sets aside its extractions at the side slopes of the river, Sueno explained.
The landlocked backhoes are responsible for taking the extracted materials, and transferring them to their trucks for disposal.
Sueno agreed that dredging is the most effective solution to perennial flooding in Marikina City.
“Kapag hindi ka nagdredge, bababaw ang ilog mo. Alam naman natin, lahat ng drainage natin dyan pumupunta. ‘Yung carrying capacity kasi ng tubig, maaapektuhan din. Pag nadredge mo na, siyempre maximum capacity, maximum volume ang [maaabot] sa ilog (If we don’t dredge, our river will become shallower. We know that all our drainage wastes end up in the river. Its carrying capacity will be affected. When we dredge, we reach the maximum capacity and volume of the river),” he said.
Sueno said Marikina City’s neighboring cities should consider mobilizing their own dredging operations.