Bicol River 2.41

Bicol River is the eight largest river in the Philippines in terms of drainage basin size with an estimated catchment area of 3,770 km². The river drains the southwestern part of the island of Luzon and passes through Camarines Surprovince in the Bicol Region.The river starts from Lake Bato, 6 metres above sea level, and flows 94 kilometres downstream to its estuarine mouth at San Miguel Bay. It passes through Naga City, the alluvial and coastal plains of the vast Bicol Valley, an elongated, northwesterly trending depression in the Bicol Region, which contains alluvial plains to the coastal plain. Average slope within the river's drainage basin is 0.006%.The basin has an influence area of 10,058 square kilometres including its drainage basin. It lies between 13°0 to 14°N and 123°0 and 124°0 E. It is extensively a coastal flood plain.GeographyGeology and GeomorphologyThe Bicol River is bounded on the northeast by the Bicol Cordillera, which consists of a chain of volcanic mountains including Mount Iriga, Mount Malinao, Mount Masaraga and Mount Mayon. On the southwestern side lie the Ragay Hills, which consists of folded and faulted sedimentary formations including limestones, siltstones, conglomerates and shale. In between these higher areas lies the Bicol plain, which is composed of thick alluvial deposits of sand silt and clay.