MMDA – Flood reduction measures in Metro Manila

September 27, 2010 briefer prepared by the Metro Manila Development Authority

INTRODUCTION

As we join the entire nation in commemoration of the victims and heroes of Typhoon Ondoy a year ago, the Metropolitan Manila Development Authority would like to share with the public, through the Malacañang Press Corps, the Agency’s current and proposed flood reduction measures for Metro Manila.

One of the important lessons learned from Ondoy is that Metro Manila’s existing rivers and waterways, drainage system and flood control systems are inadequate to accommodate and discharge the extraordinary and extreme volume of rainwater experienced during that fateful day in 2009.

Based on the data gathered by the Manila Observatory, the total rainfall on that day was measured at 368.6 millimeter which is higher than the 330.3 millimeter average monthly rainfall for September resulting to the massive flooding in the metropolis and neighboring provinces.

MAJOR CAUSES OF FLOODING IN METRO MANILA

However, everyone should be aware of the real causes of flooding in Metro Manila which include the following:

1. Rapid urbanization and development which caused the almost zero absorption of rainwater by the ground due to the highly built-up status of Metro Manila resulting to doubled surface runoff of flood waters.

2. Clogging and siltation of drainage laterals and waterways due to indiscriminate dumping of garbage which obstruct the free flow of water.

3. Structural obstructions, encroachment and presence of informal settlements along open waterways which impede the flow of water.

4. Inadequate flood control structures and limited capacity of existing drainage systems which generally cannot accommodate excessive floodwaters

5. Lack of integrated land use plans which results to the inefficient allocation, use and management of land and other physical resources of the metropolis.

6. Excessive and intense rainfall due to climate change which has resulted to the increased frequency of extreme weather events such as La Nina.

In view of these findings, there is an urgent need to come-up with an integrated flood control plan in Metro Manila to address the gap in our flood control capabilities.

SITUATIONER

The current drainage system in Metro Manila is composed of 580 kilometers of open waterways, 897 kilometer of drainage laterals and 58.97 kilometers of drainage mains and interceptors.

It is estimated that 30 percent of open waterways are not accessible to flood control equipment due to illegal encroachment.

In addition to the existing drainage system, Metro Manila has the Manggahan Floodway facility which is composed of the Rosario Weir Control Station with 8 floodgates.

This 100-year return period structure was designed to limit the floodwaters in the lower Marikina River and the Pasig River to its bank-full capacity by diverting the excess floodwaters into the Laguna Lake for temporary storage.

Another major flood control facility is the Napindan Hydraulic Control Structure which is composed of 4 floodgates and 2 navigational lock gates.

The structure is designed to improve the quality of the Laguna Lake water by preventing the backflow of saline and polluted water from the Pasig River into the lake, making the lake water usable for irrigation, domestic and industrial purposes.

The Effective Flood Control Operation System or EFCOS is primarily designed for the effective operation of the Manggahan Floodway and the Napindan Hydraulic Control Structure.

At present, the EFCOS is operational with three (3) rainfall stations located in Mt. Aries, Boso-Boso and Mt. Oro. it has five (5) water level stations located in Montalban, Rosario, Pandacan, Fort Santiago and Angono.

The system also has nine (9) warning stations equipped with sirens along the Manggahan Floodway to warn the residents living along the floodway once floodgates are opened to allow excess floodwaters from Marikina River to flow to the Laguna Lake for temporary storage.

In addition, MMDA operates and maintains 52 pumping stations consisting of 20 large pumping stations, 10 small pumping stations and 22 relief pumping stations in strategic locations in the Camanava Area.

As of August 31, 2010, MMDA has dredged 40,427 linear meters of open waterways, declogged 277,779 linear meters of drainage laterals and desilted 2,309 linear meters of drainage mains and interceptors.

ON-GOING FLOOD CONTROL ACTIVITIES

Under the leadership of Chairman Francis N. Tolentino, the MMDA has initiated the following flood control activities:

1. ‘Estero Declaration’ which was signed by the Mayors of the 17 LGUs and MMDA wherein they all pledge and commit to protect and clean-up Metro Manila’s waterways

2. ‘Oplan Unos’ which is part of MMDA’s operational readiness during the rainy season. This initiative of Chairman Tolentino involves the setting-up of a command center which will manage the deployment of “composite teams” comprising of around 300 MMDA personnel and volunteers per team equipped with appropriate flood and rescue equipment.

3. Citizen Disaster Volunteers were engaged to augment MMDA’s personnel during flooding and other disasters.

4. ‘Lingap sa Barangay’ which is a clean-up drive aimed at helping depressed and densely populated communities prevent flooding which causes leptospirosis and the spread of diseases such as dengue. The clean-up drive kicked off last 3 September 2010.

5. ‘Anti-Littering Law’ which was re-launched last September 16, 2010 along EDSA.

6. ‘Anti-Dengue Initiative through fogging operations in public schools in Metro Manila last September 3, 2010.

7. ‘Public Private Partnership’ which is part of the agency’s initiatives in encouraging the active involvement and assistance of the private sector in de-silting and de-clogging of drainage mains and laterals and open waterways.

8. ‘Flood Control Bayanihan Zones’ wherein flood-mitigation activities in these flood-prone areas shall be managed by a community-based alliance composed of representatives from civic organizations, business establishments, religious groups, non-government organizations, people’s organizationsm and the local government in partnership with other government agencies and the MMDA.

PROPOSED FLOOD CONTROL PROJECTS

In addition to these on-going activities, the MMDA is proposing immediate and long-term projects to help eradicate flooding incidents in the major flood prone areas:

1. Construction of new pumping stations and installation of additional pumps to increase capacities in draining floodwaters.

2. Widening and dredging of rivers, creeks and esteros to their desired depth and width to improve conveyance capacities of these waterways.

3. Removal of informal settlers and other structural obstructions/encroachments located along the rivers, creeks and esteros.

4. Upgrading of existing drainage systems and structures such as interceptors and laterals.

5. DPWH’s proposed construction of a 100-km Laguna Lake Ring Road Dike including 11 bridges and 10 pumping stations.

6. DPWH’s proposed construction of the Marikina Dam to control the on-rush of excessive floodwaters from the mountains of Rizal and upper Marikina River.

7. Construction of an 8-km Flood By-pass to augment the Napindan Channel and Manggahan Floodway.

www.mmda.gov.ph