Metro Manila, with a total population of over 11.1 million in 2007, is the economic, political and cultural center of the Philippines. The Pasig Marikina River, having a total catchments area of 621 km2, runs through the core of Metro Manila and flows into the Manila Bay. The river may cause severe flooding in Metro Manila by the overbanking flow of floodwater during heavy rains.

To find solutions to the flooding and the environmental problems associated with the river improvement works, studies have been conducted since 1988. The main component of this project is the river channel improvement that consists of the construction and rehabilitation of revetments, parapet walls/river walls and soil embankments, and the construction of the Marikina Control Gate Structure that functions to divert floodwater from the upstream through the Mangahan Floodway to mitigate the flood damage in Metro Manila. At the present stage, the project is ongoing in multiple stages and the construction works are financed through the Japan Bank for International Cooperation (JBIC) Loan.