Manggahan Floodway

A lifeline carved through the earth, the Manggahan Floodway stretches before us. This vital artery plays a crucial role in protecting Manila from the Marikina River’s fury. The Manggahan Floodway, an engineering marvel, was completed in 1986 at a cost of 1.1 billion pesos. Its purpose is simple yet profound: to redirect excess water from the Marikina River during the rainy season, preventing devastating floods in Manila. The Manggahan Floodway diverts this water to Laguna de Bay, a vast lake that acts as a temporary reservoir. Interestingly, this flow can be reversed if the lake’s water level surpasses that of the Marikina River. The Manggahan Floodway is designed to handle an impressive 2,400 cubic meters of water per second. However, due to various factors, the actual flow typically reaches around 2,000 cubic meters per second. Complementing the floodway is the Napindan Hydraulic Control System. Built in 1983, this system manages the delicate balance of saline water between Manila Bay and Laguna de Bay. It also prevents polluted water from entering the lake. At its head, the Manggahan Floodway boasts a fully gated diversion dam. Originally designed with a width of 260 meters, its effective width has been reduced to 220 meters due to informal settlements along its banks. Over 40,000 households are located along these banks. A stark reminder of the complexities of urban development. These communities often cultivate kangkong, a semi-aquatic vegetable, within the floodway. Originally, the Manggahan Floodway was intended to work in conjunction with the Paranaque Spillway Project. This project aimed to further alleviate flooding by channeling excess water from Laguna de Bay to Manila Bay. Unfortunately, due to budget constraints, the Paranaque Spillway Project was canceled in 1977. However, after Typhoon Ondoy in 2009 and subsequent recurring floods, discussions about reviving the project have emerged, along with proposals for a Marikina Dam. The Manggahan Floodway stands as a testament to human ingenuity and the ongoing struggle against the forces of nature. It is a vital part of Manila’s flood control infrastructure. A constant reminder of the city’s vulnerability.