Manggahan Floodway

The Manggahan Floodway is an artificially constructed waterway in Metro Manila, Philippines. The floodway was built in 1986, at a cost of 1.1 billion pesos, in order to reduce flooding along the Pasig River during the rainy season, by diverting the peak water flows of the Marikina River to Laguna de Bay, which serves as a temporary reservoir. If the water level on the lake is higher than the Marikina River, the floodway's flow can be reversed. By design, the Manggahan Floodway is capable of handling 2,400 cubic meters per second of water flow, although the actual flow is about 2,000 cubic meters per second. To complement the floodway, the Napindan Hydraulic Control System (NHCS) was built in 1983 at the confluence of the Marikina River and the Napindan Channel of the Pasig River to regulate the tidal flow of saline water between Manila Bay and the lake, and to prevent the intrusion of polluted water into the lake. It has a fully gated diversion dam at its head and was designed with a width of 260 meters (850 ft). Over 40,000 households are situated along the floodway's banks and these shoreline slums have reduced its effective width to 220 meters (720 ft). Kangkong is cultivated extensively in the floodway as well. The Manggahan Floodway was supposed to function together with the proposed Paranaque Spillway Project, a spillway that would direct flood waters from Laguna de Bay t

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