The Bicol River is the eighth largest river in the
Philippines
The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no),
* bik, Republika kan Filipinas
* ceb, Republika sa Pilipinas
* cbk, República de Filipinas
* hil, Republ ...
in terms of
drainage basin
A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
size with an estimated catchment area of . The river drains a large part of southwestern
Bicol Peninsula
Bicol, known formally as the Bicol Region or colloquially as Bicolandia ( bcl, Rehiyon kan Bikol; Rinconada Bikol: ''Rehiyon ka Bikol''; Waray Sorsogon, Masbateño: ''Rehiyon san Bikol''; tl, Rehiyon ng Bikol), is an administrative region of ...
of the island of Luzon and passes through
Camarines Sur
Camarines Sur ( bcl, Habagatan na Camarines; tl, Timog Camarines), officially the Province of Camarines Sur, is a province in the Philippines located in the Bicol Region on Luzon. Its capital is Pili and the province borders Camarines Norte a ...
province.
The river starts from
Lake Bato
Lake Bato is a freshwater lake and the 7th largest in the Philippines. It is located in the town of Bato, approximately southwest of Iriga City, Camarines Sur Province, southeastern Luzon, Philippines. It has extensive marshes and swamp forests ...
,
above sea level, and flows downstream to its
estuarine
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...
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 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
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
.
Geology and geomorphology
The Bicol River is bounded on the northeast by the
Bicol Cordillera, which consists of a chain of
volcanic mountains including
Mount Iriga
Mount Iriga, also known as Mount Asog, is an active stratovolcano in the province of Camarines Sur, in the Philippines.
It is a stratovolcano about a kilometer from Lake Buhi. It rises with a base diameter of . It has a large crater formed du ...
,
Mount Malinao
Mount Malinao is a potentially active stratovolcano located in the Bicol Region of the Philippines. The volcano displays strong fumarolic activity which is harnessed for generating electricity. Located on its slope is Tiwi Geothermal Power Plan ...
,
Mount Masaraga and
Mount Mayon. On the southwestern side lie the
Ragay Hills, which consists of folded and faulted sedimentary formations including
limestones
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms when t ...
,
siltstones
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...
,
conglomerates and
shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...
. In between these higher areas lies the Bicol plain, which is composed of thick
alluvial deposits
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...
of
sand silt and
clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay pa ...
.
The main geo-morphological features found in the area include the
estuarine
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...
plain, a river flood plain, the
piedmont plain and the valleys of incised creeks. The estuarine plain is level to nearly level and consists of fine fluvial-marine deposits over sandy layers with marine shells. The fluvial marine deposits are usually saline at depths of approximately and includes depresses areas along the Bicol River. The river floodplain is made up of mixed alluvium. The piedmont plain on the fringe of the
Ragay Hills consists of fine alluvium clay and reworked
colluvium
Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, sheetwash, slow continuous downslope creep, or a variable combinati ...
s.
Climate
The climate is influenced by the Northeast Monsoon winds and the
Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...
trade winds. These
Monsoon
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
winds create the
low pressure area
In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather (such as cloudy, windy, with possible ...
in the Pacific Ocean, resulting in
tropical cyclones
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Dependi ...
that affect the area in November and December.
Rainfall
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
occurs throughout the year with low rainfall between January to May and high rainfall between June and December. In the lower basin, mean annual rainfall ranges between . The main factors influencing rainfall are the
air streams, the
intertropical convergence zone
The Intertropical Convergence Zone (ITCZ ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the thermal ...
and
topography
Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps.
Topography is a field of geoscience and planetary sc ...
.
The mean temperatures are high throughout the year with the daily mean temperatures in the range of and an annual mean temperature of .
Crossings
This is listed from mouth to source.
# Malbong Hanging Bridge (
Gainza, Camarines Sur
Gainza, officially the Municipality of Gainza ( bcl, Banwaan kan Gainza; tl, Bayan ng Gainza), is a 4th class municipality in the province of Camarines Sur, Philippines. According to the 2020 census, it has a population of 11,584 people.
Gainza ...
)
# Old Mabolo Bridge (Felix Plazo Street,
Naga
Naga or NAGA may refer to:
Mythology
* Nāga, a serpentine deity or race in Hindu, Buddhist and Jain traditions
* Naga Kingdom, in the epic ''Mahabharata''
* Phaya Naga, mythical creatures believed to live in the Laotian stretch of the Mekong Ri ...
–
Milaor
Milaor, officially the Municipality of Milaor ( bcl, Banwaan kan Milaor; tl, Bayan ng Milaor), is a 3rd class municipality in the province of Camarines Sur, Philippines. According to the 2020 census, it has a population of 33,963 people.
Milaor ...
boundary)
# Unnamed
Philippine National Railways
The Philippine National Railways (PNR) ( fil, Pambansang Daang-Bakal ng Pilipinas and es, Ferrocarril Nacional de Filipinas) is a state-owned railway company in the Philippines which operates one commuter rail service between Metro Manila a ...
bridge,
Naga
Naga or NAGA may refer to:
Mythology
* Nāga, a serpentine deity or race in Hindu, Buddhist and Jain traditions
* Naga Kingdom, in the epic ''Mahabharata''
* Phaya Naga, mythical creatures believed to live in the Laotian stretch of the Mekong Ri ...
–
Milaor
Milaor, officially the Municipality of Milaor ( bcl, Banwaan kan Milaor; tl, Bayan ng Milaor), is a 3rd class municipality in the province of Camarines Sur, Philippines. According to the 2020 census, it has a population of 33,963 people.
Milaor ...
boundary
# Mabolo Bridge (,
Naga
Naga or NAGA may refer to:
Mythology
* Nāga, a serpentine deity or race in Hindu, Buddhist and Jain traditions
* Naga Kingdom, in the epic ''Mahabharata''
* Phaya Naga, mythical creatures believed to live in the Laotian stretch of the Mekong Ri ...
–
Milaor
Milaor, officially the Municipality of Milaor ( bcl, Banwaan kan Milaor; tl, Bayan ng Milaor), is a 3rd class municipality in the province of Camarines Sur, Philippines. According to the 2020 census, it has a population of 33,963 people.
Milaor ...
boundary)
# FVR Bridge I (
Milaor, Camarines Sur
Milaor, officially the Municipality of Milaor ( bcl, Banwaan kan Milaor; tl, Bayan ng Milaor), is a 3rd class municipality in the province of Camarines Sur, Philippines. According to the 2020 census, it has a population of 33,963 people.
Milaor ...
)
# Unnamed bridge in
Bula, Camarines Sur
Bula, officially the Municipality of Bula (Rinconada Bikol: ''Banwaān ka Bula''; Tagalog: ''Bayan ng Bula''), is a 1st class municipality in the province of Camarines Sur, Philippines. According to the 2020 census, it has a population of 73,14 ...
# Sto. Domingo Bridge (Nabua–Balatan Road,
Nabua, Camarines Sur
Nabua, officially the Municipality of Nabua (Rinconada Bikol: ''Banwāan ka Nabua''; Tagalog: ''Bayan ng Nabua''), is a 1st class municipality in the province of Camarines Sur, Philippines. According to the 2020 census, it has a population of 8 ...
)
References
{{Principal Rivers of the Philippines
Rivers of the Philippines