As a major service of PAGASA, flood forecasting is mandated by Presidential Decree (PD) 78 dated December 8, 1972 as amended by PD 1149, dated June 8, 1977. To implement this mandate,
the National Flood Forecasting Office (NFFO) was created.
The Hydrometeorology Division (HMD), formerly known as the Flood Forecasting Branch (FFB), consists of the Office of the Division Chief and three sections, namely: the Flood Forecasting
and Warning Section (FFWS), Hydrometeorological Data and Special Studies Section (HMDSS) and Hydrometeological Telemetry Section (HMTS).
HMD, through the FFWS administers flood forecasting and warning (FFW) operations for the entire country. This is carried out through its Main Operations Center (MOC) based in PAGASA Main
Office in Quezon City and River Flood Forecasting and Warning Centers (RFFWC) in their respective forecasting areas. At present, there are ten (10) RFFWCs in the country.
They are: the Pampanga, Agno, Bicol, Cagayan and Pasig-Marikina River Basins in Luzon; Panay and Jalaur River Basins in the Visayas; and Cagayan de Oro, Mandulog and
Tagum-Libuganon River Basins in Mindanao.
MOC is the lead group that manages all FFW aspects, from river basin to dams and reservoirs.
It acts as the supervisory/coordinating center for various river centers which perform the following functions:
MOC is also the lead center for the inter-agency Flood Forecasting and Warning System for Dam Operation (FFWSDO) and the FFWS for Metro Manila (covering Pasig-Marikina-Tullahan River Basins).
The latter is in collaboration/partnership with the Effective Flood Control Operation System (EFCOS) of the Metro Manila Development Authority (MMDA) which operates the Mangahan Floodway
and a separate network of telemetered gauging stations.
The Pasig-Marikina River is the main river basin in Eastern Metro manila, stretching from Rodriguez, Rizal down to Pasig City passing through San Mateo and Marikina City. The 40 kilometer river flows
in the center of Marikina Valley between the mountain ranges of Sierra Madre in the east and Quezon City in the west. Its depth ranges from 3 to 21 meters and spans from 70 to 120 meters. It is one of
the main tributaries of the Pasig-Marikina-Laguna de Bay basin with a drainage area of 535 square kilometers. A portion of its flow is controlled and diverted by the Manggahan Floodway to Laguna
Lake. The remaining water is drained to Manila Bay through Pasig River.
Marikina River runs in the heartland of Marikina Valley passing through heavily populated residential areas throughout its length and through important commercial and industrial areas at its middle
and downstream portions. The river regularly overflows its banks and floods the surrounding basin during periods of heavy rains.
Tropical Storm Ondoy (Ketsana) which crossed Metro Manila on 26 September 2009 caused Marikina River to reach its highest water level recorded, resulting to heavy loss of lives and properties.
TS Ondoy dumped 455 millimeters of rain in Metro Manila and its environs in just a span of 9 hours - the highest recorded in 42 years. A month’s worth of rainfall in a single day washed away homes
and flooded large areas, stranding thousands on rooftops in the metropolis and elsewhere. There were 464 casualties and the damage was estimated to have reached USD100 million.
A month after the “Ondoy” episode, the Korean Government immediately decided to provide long term assistance through the establishment of an early warning system for disaster mitigation in
Metro Manila or the EWS-2 Project. The project includes data collection/flood forecast/early warning system and radio communication network which serve as the backbone of the entire system.
Flood monitoring equipment were deployed within Pasig-Marikina River comprising of 10 Raingauge Stations, 10 Waterlevel Gauging Stations, 4 Automatic Weather Stations and 20 Warning Post
Stations which became the highlight of the project. The entire system aimed to complement the EFCOS Project of MMDA and focused mainly to forewarn the people along Marikina and Pasig River.
The effectiveness of the system had prompted the Korean Government to expand the project covering the northwestern parts of Metro Manila that are also perennially flooded. Thus, the EWS-3
Project came to reality.
Similar to the EWS-2 Project, the EWS-3 Project deployed and installed additional (10) rainfall gauging stations and (2) water level stations and (2) CCTV stations along the Pasig-Marikina River Basin
at the selected cities of Rizal Province, Marikina and Mandaluyong while (3) rainfall gauges and (4) water level gauges, (5) CCTV stations, (1) Relay Station and (14) warning posts were installed at the
Tullahan River Basin in Quezon City, Caloocan, Malabon, Navotas and Valenzuela. Similar to the warning posts installed at Pasig-Marikina, the warning posts for Tullahan River have a 3-tone siren that corresponds to different warning levels (Alert, Alarm and Critical levels) at each forecasting point. These warning levels are unique for each forecasting points that was determined thru a hydrographic survey that were also undertaken in this Project.
The data collected in the remote sites are automatically transmitted via Radio-Based Communication which will be monitored at the newly established Command Center, in real time. These can be
viewed utilizing the software developed under the project which includes real time monitoring, equipment monitoring, quality management and web-based system.
One of the important features of the EWS-3 Project is the modification of the former FFW program for Metro Manila and development of an operational Flood Forecasting Model for Pasig-Marikina and Tullahan River Basins, integrating all historical and new hydrological data, including radar images.
The establishment of Flood Forecasting and Warning System Operations Center for Pasig-Marikina-Tullahan River Basin offers a state-of-the-art technology that specifically caters to the growing
needs of the Metropolis for effective flood warning information. This will complement the quality service which PAGASA aims to provide for Metro Manila residents by mitigating damages caused by