The Marikina River has a rich history dating back to the Spanish colonial era when it served as a vital transport route.¹ Originating from the Sierra Madre mountains in Rodriguez, Rizal, the river stretches 78 kilometers and flows through several cities, including San Mateo and Marikina, before emptying into the Pasig River.  Early Years and Importance The river's significance waned with the development of the national highway system, leading to reduced river boat traffic and subsequent siltation. This siltation was further exacerbated by deforestation in the Upper Marikina River Basin Protected Landscape.  Tributaries and Waterways The Marikina River has several tributaries, including the Tayabasan River, Montalban River, Boso Boso River, and Wawa River, which drain into the river before it flows into the Wawa Dam. Other notable tributaries include the Puray River, Manga River, Ampid River, and Nangka River.  Ecological Concerns In recent years, the river has faced ecological challenges due to pollution and the invasion of non-native species, such as the janitor fish, which has dominated the river's ecosystem. Efforts have been made to control the population and restore the river's natural balance.  Significant Floods The Marikina River has been prone to severe flooding, particularly during typhoons and heavy rainfall events. Notable instances include:   - Typhoon Ketsana/Ondoy (2009): The river burst its banks, flooding 80% of Metro Manila and displacing thousands. - Typhoon Meari/Falcon (2011): The river reached critical levels, but no casualties were reported. - Typhoon Nesat/Pedring (2011): The river submerged houses in several barangays. - Typhoon Vamco/Ulysses (2020): The river surpassed its previous record water level, causing widespread flooding. (flood emergency, natural disasters floods & flood information)