Representatives of the University of the Philippines (UP) Resilience Institute (UP RI) – Nationwide Operational Assessment of Hazards (NOAH) Center participated in the recent 4th Quarter Solid Waste Management Board (SWMB) and Task Force Manila Bay (TFMB) Joint Meeting on December 19, 2023, held at the City Architect Department Conference Area in the Quezon City Hall Compound. The meeting was organized to obtain updates on the City’s solid waste management plans and activities, as well as the campaigns for the rehabilitation of Manila Bay.
Since the City is obliged by the Writ of Continuing Mandamus of the Supreme Court through the Manila Bay Clean-Up, Rehabilitation, and Preservation Program to formulate a Drainage Master Plan (DMP) to address issues and problems brought about by flooding, one of the meeting’s agenda was the discussion on the case study done by UP RI on San Juan River through the Quezon City Drainage Master Plan (QCDMP) Project. The formulation of the QCDMP will help provide solutions to the existing flooding problems of the City and will serve as the long-term framework for flood management projects.
This joint meeting is headed by the Department of Sanitation and Cleanup Works of Quezon City (DSQC) and participated by ACA Alberto Kimpo (OCA), representatives from the Quezon City Disaster Risk Reduction and Management Office (QCDRRMO), Barangay and Community Relations Department (BCRD), Business Permits and Licensing Department (BPLD), City Planning and Development Department (CPDD), City Engineering Department (CED), City Architect Department (CArD), City Health Department (CHD), Schools Division Office (SDOQC), Department of Building Officials (DBO), Department of Public Order and Safety (DPOS), General Service Department (GSD), Public Affairs and Information Services Department (PAISD), Parks Development and Administration Department (PDAD), and other relevant offices. UPRI was represented by Ms. Patricia Anne Delmendo, the Project Coordinator and member of the Project Management Team for the QCDMP Project, and Engr. Genarro Pascual, both are researchers from the Flood Modelling Component of the UP RI – UP NOAH Center.
Ms. Delmendo discussed the importance of improving drainage efficiency as it reduces inland flooding by routing more floodwater to natural channels. As such, there is a need to evaluate if the natural channels can accommodate flood discharge and overflow from the drainages. She further explained the methods used in determining the channel capacity for steady and uniform flow with the use of Manning’s Equation and 2D simulation of bank full flow using Flo-2D.
Engr. Genarro Pascual presented the findings and the hydrologic analysis done in the QCDMP for San Juan River. He provided insights into the river’s capacity and identified which sections of the river are likely to flood as a result of backflow and constriction. He also mentioned that while the 2D simulation takes into account the water that does not make it into the rivers and tributaries, the timing calculated from comparing the results of the models is that it assumes that all the water upstream eventually makes its way downstream and flood water exiting junctions within a river’s catchment area will make its way to the river.
The UP RI researchers also highlighted that accurately assessing the capacity of river channels would depend on accurate input data. They suggested having a complete inventory of the drainage system to have a reliable measure of water flowing into the rivers under different rainfall scenarios and establishing an updated digital elevation model of the city. Collected and digitized as-built drawings of manmade interventions that might affect the river capacity will be helpful, too.
Finally, the discussion mentioned some of the infrastructure projects that can be utilized by the local government such as the possible use of steel nets as trash traps and the construction of detention basins to delay peaking. UP RI believes that calibration is an integral part of creating an accurate model, and a calibrated model can be used as a baseline for predictive modeling. Actual flood data from the sensors of QC can also be used to calibrate models to simulate previous rainfall scenarios experienced in the City. UP RI will continue to collaborate with the local government of Quezon City and support its efforts to provide solutions and mitigate the effects of flooding.