IT’S been almost six years since Typhoon Ondoy submerged the streets and neighborhoods of Metro Manila. But until now, it seems that we are still unprepared for Nature’s vengeance. According to the latest research presented to the UN regarding environmental issues, extreme weather conditions will continue to worsen and are expected to become more frequent. We need to face the reality that flooding is a comprehensive effect of extreme weather conditions and climate changes coupled with rapid growth, urban expansion without proper planning and implementation, abuse of lakes and rivers, deforestation and illegal logging.
It was in the late 1970’s that flood projections and recommendations for Metro Manila were made. Aside from the fact that the plan was to determine the exact areas that will be submerged, which were seen in the event of Ondoy and Habagat, the development of Laguna Lake and the Parañaque Spillway were also proposed and recommended.
Laguna Lake and Parañaque Spillway
There are two major catch basins for Metro Manila —Laguna Lake and Manila Bay. In between them are two major rivers – Pasig River and Marikina River. But when storm surges occur, there is a major problem in the flow of water. It clogs at the intersection point which is Pasig River. And the consequence, is Marikina and Pasig Rivers spill over. The Pasig River and Laguna Lake do not have the capacity to accommodate all the flood waters coming down the mountains.
The water that flows down from the mountain of Antipolo towards Marikina River is diverted by the Manggahan floodway and directs excess water to flow towards Laguna Lake. But for cities near Pasig River, water is pumped towards the river and ideally will flow out to Manila Bay. The problem here is that when Laguna Lake is overfilled with flood waters, it will need to pass through Pasig River before it exits Manila Bay. Hence, the water reaches critical level because of the bottleneck and eventually result in major floods. During Ondoy, more than 4,000 cubic meters per second flowed down the mountains. Pasig River only had a capacity of 600 cubic meters. This resulted in the flooding of approximately 80,000 hectares of urban land. If the proposals for the Spillway and dredging of the Laguna Lake and rivers were carried out, the floods would not have been that bad.
The Parañaque Spillway was a proposed project that would have allowed water from Laguna Lake to flow directly towards Manila Bay instead of flooding the Lakeshore towns of Laguna, Rizal, and Metro Manila. Metro Manila still needs the Spillway or a SMART Tunnel like that in Malaysia. Another probable solution to mitigate a spill over is the regular deepening of our rivers, esteros, and most especially Laguna Lake.
We should consider the geographic composition of Metro Manila compared to those in Malaysia, Japan and Singapore. We already have natural catch basins and water systems to mitigate our flood problems. In perspective, Laguna Lake is much bigger than Metro Manila. Its surface area is 949 km2 compared to Manila’s 638.55 km2. It is even much bigger than Singapore (718 km2) and Kuala Lumpur (243 km2). It used to be seven meters deep. Reportedly, it is now only two-and-a-half meters deep.
On the other side
It would be wrong to assume that Metro Manila faces this problem in isolation. Our ASEAN neighbors are feeling the brunt of nature as well. But what makes it different is that our neighbors have systems and infrastructures in place to prevent similar situations that Metro Manila experiences. We can take a look at their solutions, and try to learn and understand how those can be applied here in our country as well.
Malaysia boasts of having the longest water tunnel in South East Asia and second longest in Asia known as the SMART Tunnel (Stormwater Management and Road Tunnel). It is 9.7 km long and serves both flood and traffic control. The main objective is to spare Kuala Lumpur from flashfloods which are now sometimes termed as ‘inland tsunamis’.
In Singapore, a more comprehensive approach to flooding and potable water has been developed. It is called the ‘source-pathway-receptor’ approach. Singapore created dedicated rain gardens and ponds that serve as catchment areas, flood barriers, diversion canals and the re-designing of drainages in the streets. The government also revised its Code of Practice on Surface Water Drainages. It also raised and made new requirement for the minimum land and reclamation levels and crest levels for new developments and redevelopments. Aside from flood mitigation and prevention, having a complete water cycle system makes sure that water is controlled, collected, treated and recycled.
Year after year, our citizens suffer the same problems but with more severity. For a longer term solution, we are already fortunate to have had previous planning, studies and recommendations from way back, which we only need to revisit, update, and implement. The answers and the latest technologies to implement them are available as well. However, it would take visionary leadership, strong political will, good planning, good design, good governance and solid public-private collaboration for us to begin seeing these plans being realized to address the hazards before they become disasters.