Geographical, Administrative/Political Profile of Sorsogon

Location and Boundaries

Sorsogon is located at the southernmost tip of Luzon Island, approximately 600 kilometers southeast of Metro Manila.  On the North extends westward from 1230 to 1240-east longitude and on the north-south axis from 120 to 130-north latitude. It is bounded on the north by the province of Albay and the Albay Gulf; on the south by Samar and the San Bernardino Strait; on the east by the Pacific Ocean; and on the west by Burias Island and Ticao Pass.  Except for its overland link with the province of Albay, it is surrounded by water.  Sorsogon is accessible to the large island province of Masbate through its port facilities in the towns of Pilar and Bulan.  Being at the tip it is also the gateway of Luzon to the Visayas and Mindanao regions through its roll-on, roll-off ferry terminal facilities located in the towns of Matnog and Bulan.

Land Area and Political Subdivisions

Sorsogon is the second smallest province among the six (6) provinces of the Bicol Region in terms of land area.  It has a total land area of about 214,144 hectares or 2,141.4 square kilometers comprising 11.80 percent of the regional total land area and 0.72 percent of the total land area of the Philippines, while that of the entire Bicol Region’s land area comprises 6.06 percent of the total land area of Philippines.

The Province of Sorsogon comprises one (1) component city and fourteen (14) municipalities.  The component city ratified under RA 8806 in 2000, merging the towns of Bacon and Sorsogon to what is now Sorsogon City, accounted for the highest land area at about 354.80 square kilometers in the province. Prieto Diaz is the least municipality in terms of land area with only 2,290 hectares or 29.9 square kilometers.

The component city/municipalities of the province are divided into two (2) congressional districts.  The first district is composed of five (5) municipalities and one (1) city.  The City of Sorsogon is the capital of the province.  The second district is composed of nine (9) municipalities.

Except for Irosin, all the municipalities including the City of Sorsogon are located along coastal zone sites, stretching the 336 kilometers long coastline of beautiful beaches from the northern portion of Sorsogon City to the municipalities of Prieto Diaz, Gubat, Barcelona, Bulusan, Sta. Magdalena and Matnog, which faces the Pacific Coast.  The towns of Bulan, Magallanes, Pilar, and Donsol are on the western side while Casiguran, Castilla, and the southwestern portion of Sorsogon City lie along the Sorsogon Bay.  Sorsogon province has five Hundred forty-one (541) barangays.

Physical Resources (General Land and Water Characteristics and Resources) 1

Topography and Slope

Sorsogon province is characterized by irregular topography.  Mountains sprawl along the northeastern part as well as on its southeast portion.  The mountain range stretches from Sorsogon province to Albay covering some parts of the Sorsogon City and Castilla.  These mountains slope down upon small valleys and plains.  These plains and mountains, though, are not only enchanting but are also good hunting grounds.  The tallest peak is Mount Bulusan with an elevation of 1,560 meters above sea level.  It is an active volcano seated at the center of five (5) municipalities and located in the southeastern part of the province.  Mt. Bintacan is another towering mountain with an elevation of 820 meters above sea level, located in the south-western part of the province occupying two (2) municipalities (Juban and Magallanes) serving as watershed areas.

Land area and Water Resources

Land area

Sorsogon is the southernmost tip Province on the island of Luzon with a total land area of 214,144 hectares spread over the fifteen (15) component city/municipalities consisting of 541 barangays.  Out of the total land area of the province, 212, 799.74 hectares cover the mainland and 1,344.2597 hectares aggregate area of ten (10) islets located in five (5) coastal city/ municipalities. Shown in Map 2. These separate islands are either a barangay or part of the mainland barangay.  Bagatao Island in Magallanes is the biggest in terms of land area with 478.01 hectares.  Tinacos Island also in Magallanes is the least among the islets in terms of land area with only 0.8 hectares.  Matnog has four (4) islets namely; Tickling Island (51.5569 hectares); Juag Island (48.355 hectares); Calintaan (260 hectares); and Morong-borongan (13.0 hectares).  Juban has two (2) islets namely; Sablayan and Batang with 292.4278 and 5.6 hectares respectively. Malawmawan Island in Castilla has 30.51 hectares, and Pinaculan Island in Sorsogon City has 3.0 hectares.

Physical Resources (General Land and Water Characteristics and Resources) 2

Water Resources

All except one (1) of the component city/municipalities lie along the 336-kilometer coastline of the province. Facing the Pacific Ocean are the towns of Prieto Diaz, Gubat, Barcelona, Bulusan, and Sta. Magdalena; along the San Bernardino Strait, fronting is Matnog; Donsol and Pilar are adjacent to Burias Pass, as Bulan and part of Magallanes is to Ticao Pass; and the municipalities of Castilla, Juban, Casiguran, Magallanes and Sorsogon City rim the shores of Sorsogon Bay.  The only inland town is Irosin, which is endowed with therapeutic hot springs and cradles a fertile valley southwest of Mt. Bulusan, an active volcano.

Mountain ranges from natural basins that collect water flow down the major river channels and their tributaries and emptied into surrounding water bodies such as the Pacific Ocean, San Bernardino Strait, the Ticao Pass, and Sorsogon Bay.

The Bacon-Castilla range serves as a watershed for Castilla and Sorsogon City.  The catchment areas and their tributaries supply the domestic, agricultural, and other water uses of Sorsogon City and Castilla.

The major water bodies include Sorsogon Bay, Cawayan River in Sorsogon City, Putiao River, in Pilar, and Cadacan River in Irosin and Juban.  Cawayan River yields the highest daily discharge of 3,040 cubic meters.  Bulusan Mountain Lake is the most famous in the province having an area of about 16.4 hectares with an elevation of about 320 meters above sea level and the tourist destination site.

The three (3) major river watersheds of the province are the Cadacan River Watershed, Ogod River Watershed, and Putiao River Watershed.  The Cadacan

River Watershed at Juban-Irosin side flows down into the Cadacan River with an area of 29,165.57 hectares and its outfall is the Sorsogon Bay; the Ogod River Watershed that flows into Donsol River and Ogod River with an area of about 6,657.47 hectares, empties into Burias Pass; and the  Putiao River Watershed that flows down into Putiao River with an area of 3,373.79 hectares and empties into Pilar Bay.  The rivers and tributaries supply the domestic and agricultural water needs of the surrounding communities.

Mt. Bulusan, which is part of the Cadacan River Watershed, is a 6,043-hectare watershed that sustains crystal spring water for domestic use, rivers for various uses, waterfalls that provide local communities the necessary water resources for recreational, domestic, irrigation water, and other purposes. This watershed covers five (5) municipalities of the province namely: Bulusan, Irosin, Juban, Casiguran, and Barcelona. The Volcano watershed is bounded by the Pacific Ocean on the east and by Burias and Ticao passes on the west.

Mt. Bintacan, which is also part of the Cadacan River Watershed, is the only area proclaimed as a watershed reservation under the title Juban Magallanes Watershed Forest Reserved (JMWFR) that contains an aggregate area of 1,032. The catchment area of this watershed and its tributaries has the potential capacity to supply water for domestic, irrigation, and other useful uses of water in the locality and the nearby communities of Juban and Magallanes.

The PNOC-BACMAN Geothermal Reservation area covers partly the Municipality of Manito in Albay, and in the Province of Sorsogon, the Municipality of Castilla, and Sorsogon City. On the Sorsogon side, the total area of 8,939 hectares is a reservation area for geothermal power where the 681 hectares serve as a source of water for domestic purposes for Sorsogon City.  The steam extracted from Bacon District and Sorsogon City to run the Bacman Geothermal Power Plants having a current aggregate capacity of 130 megawatts supplies electric power to the Luzon Grid.

Mt. Kabigaan and Mt. Guinsayawan in the municipality of Sta. Magdalena is the major watershed area of this municipality and the source of potable water and other water uses.  The water that comes out from the slopes of Mt. Kabigaan flows out into the Wenaclean and San Isidro Rivers and finally empties into the Pacific Ocean.  The water from the slopes of Mt. Guinsayawan flows out into Dugyang River and finally into the Pacific Ocean

The main water bodies that surround the province of Sorsogon are; Ticao Pass, Burias Pass, San Bernardino Strait, and the Pacific Ocean.  White sand beaches are found along the shorelines of Sta. Magdalena, Bulusan, Barcelona, Gubat, Prieto Diaz, and Bacon, embracing the Pacific Ocean.  These areas are tourism destination sites.

Sorsogon Bay is the fishing ground of the municipalities of Magallanes, Juban, Casiguran, Castilla, and Sorsogon City. However, due to the red tide infestation of Sorsogon Bay, the surrounding fishing communities are greatly affected.  The livelihood of fishing communities, especially, those along Juban, Casiguran, and Sorsogon City shorelines, are dependent on oyster and mussel culture and production, whose production, due to red tide occurrence has dwindled adding to the poverty situation of the affected communities.

Burias Pass and Ticao Pass are abundant sources of marine products, specifically fish catch, as shown by the volume of daily fish unloading on landing sites. Bulan has the highest daily unloading followed by Magallanes and Donsol. Of the municipalities bordering the Burias Pass, Pilar has the least daily fish unloading.  The presence of the most famous whale shark or “butanding” could be found at Burias Pass where the shoreline of Donsol and Pilar lies.  Appearance of this great fish brought economic growth to the Municipality of Donsol where it became a major tourist attraction.

Other Physical Features


Mt. Bulusan is the most famous mountain known not only in the province of Sorsogon but also in the entire Bicol region.  Because of its unique biodiversity, it was proclaimed as a National Park under Proclamation No. 811 on June 7, 1935, and on November 27, 2000, under Proclamation No. 421, it was proclaimed as a protected area under the category of Natural Park.  The Bulusan Volcano Natural Park (BVNP) has an area covering 3,673 hectares.  It spans five (5) municipalities of the province namely: Bulusan, Irosin, Juban, Casiguran, and Barcelona.  It is a major tourist destination of the province with Bulusan Mountain Lake as its main attraction.  To safeguard its biodiversity, the Protected Area Management Board (PAMB) was organized and established to oversee the proper management of the park.  This mountain is a watershed that supports the lakes, rivers, springs, and falls, which supply the domestic and agricultural needs for water of the surrounding communities.  Although the forest cover of this mountain suffers from man-made destruction, Bulusan is still admired by many because of its green foliage and plants.  Since it is an active volcano, it is a threat that brings destruction to the surrounding communities when it erupts.  During the last eruption barangays, Cogon and Patag in Irosin were greatly affected resulting in the relocation of residents, henceforth a 4.0-kilometer radius danger zone around the volcano was established and strictly enforced.

Mt. Bintacan is a watershed reservation area proclaimed under Proclamation No. 108 dated November 23, 1992, and now known as Juban-Magallanes Watershed Forest Reserve.  The watershed totals 1,032 hectares in area and covers the municipalities of Juban and Magallanes.  It is capable of providing an abundant supply of water for domestic and agricultural usage. A Protected Area Management Board (PAMB-JMWFR) was also established to oversee proper management of the protected area.

Mt. Maraot Banwa in Sta. Magdalena is a major watershed area that serves the surrounding town and the adjoining municipality of Irosin.  Mt. Jormajam is a major watershed that also serves the municipalities of Irosin and Juban.

Physical Resources (General Land and Water Characteristics and Resources) 3

Rivers and Creeks

There are six (6) major river systems in the province of Sorsogon, namely; Cadacan River, Donsol River, Ogod River, Putiao River, Sibago River, and Tinanogan River.

Cadac-an River along the Irosin-Juban Valley forms the longest river system that almost cuts the provincial land area with a length of 62.923 km.  This river originates from the slope of Mt. Bulusan to Mt. Mara-ot Banwa ranges in Irosin, passes through Juban, and finally empties to Sorsogon Bay.

Donsol River and Ogod River are the two major rivers in the municipality of Donsol. Donsol River is the most extensive having a drainage area of 396 sq. km. The headwater of this river system is from Jovellar in the Province of Albay. This river system cuts the Municipality of Donsol having a length of 24.776 km., which outflows into Burias Pass.  Ogod River plays a major part in the local tourism industry, as its banks are home to a swarm of fireflies, which is the main attraction for the tourist riding in a boat at nighttime.  Firefly watching is now an activity that brought economic life along the riverbanks.

Ogod River is much smaller than the Donsol River. The drainage area is about 122 sq. km. or about 9.571 km that flows out into Burias Pass. The eastern side of the drainage falls within the jurisdiction of the municipality of Pilar. Sibago River and Tinanogan River are smaller rivers within the Municipality of Donsol with drainage areas of 29.9 sq. km. and 13.73 sq. km. respectively.  Ogod River is the physical boundary that separates Pilar and Donsol.

Putiao River is the major river found in the Municipality of Pilar.  Putiao River is a 13.825 kilometer that originates from the tributaries coming from Albay Province forming this big body of water with outflow to Panlatuan Bay and Ticao Pass.

Land Use

Land Use Classification

 The land area of the Province is about 214,144 hectares. Its land classification consists of two types: certified alienable and disposable (A&D) land and forestland. The A&D land has the biggest area the covers about 178,397 hectares or 83.31 percent of the total land area and the forestland is 35,747 hectares or 17.15 percent of the provincial total land area.

Forestland is categorized into unclassified forestland with a land area of 8,477 hectares 23.71 percent of the forest land area and classified forestland with a land area of 27,270 hectares or 76.29 percent other forestland area.

Within the classified forestland, established forest reserves got the highest percentage share of 5.26 percent followed by established timberlands of 5,685 hectares or 2.65 percent and the list is the mangrove or swamp forest reserves at 0.47 percent.

Meanwhile, forest land is still found in the northern portion of the province surrounding the Bacon-Manito (Bacman) Geothermal Facilities, in the southern part of Castilla; around the Mt. Bulusan National Part and Mt. Bintacan Watershed area. However, there are forest zones that are now being used for non-forest purposes and these are largely found in the Matnog-Bulan boundary, and Irosin-Bulusan-Sta. Magdalena intersections.

Physical Resources (General Land and Water Characteristics and Resources) 4

Climate and Weather

Generally, two wind streams, the Monsoons and the Pacific Trade Winds, influence the Province of Sorsogon. The Northeast monsoon occurs during November and December. It reaches Sorsogon from the eastern part of the province forming a weak stream from October, becoming stronger in November to December, and disappears in January. The southeast monsoon usually appears in June, gradually increases up to September, and decreases in October.

The northerly Pacific trade winds coming in over the eastern section of the province considerably reduce the effect of the northeast monsoon wind on rainfall from February to March extending to April and May. The southerly Pacific trade wind and the southwest monsoon influence the rainfall distribution from June to October.

The transition period between the trade wind season and the southwest monsoon occurs in mid-May, wherein rainfall distribution during this transition is determined by topography. When the warm and humid southwest monsoon passes the western side of the province, the amount of moisture is reduced and low rainfall is experienced. Moreover, when the transition period in October occurs, tropical cyclones and intertropical convergence zones bring a considerable amount of rain to the province.

The highest wind speed is experienced during June to August and November to February. This has always been associated with typhoons crossing the area. The Province of Sorsogon lies along the typhoon belt where typhoons are frequently experienced. An average of 20 times a year of typhoons has been recorded. The vulnerability of natural calamity/disasters and the abnormal change in climate cause tremendous disturbance in crops and properties.

Under the Corona Climate Classification system, Sorsogon falls under Type IV climate. Type II climate refers to no dry monsoon but with very pronounced maximum rain periods from November to January. The type IV climate is with rainfall more or less evenly distributed throughout the year that starts from October and lasts through January. It is experienced in the municipalities of Donsol, Bulan, and Matnog, while the rest of the city/municipalities experienced type II climate.  The wettest months are November, December, January, and February while the dry months are from April to June.

The annual rainfall variability obtained from eight-year rainfall data from 2005 to 2012 measured from collections sites in the municipalities of Bulan, Irosin, Donsol, and Magallanes and in Sorsogon City conforms to the Corona Climate Classification system.  During the eight years, the months with the highest rainfall occurred during December with an average of 618mm to January with an average of 534mm. The months with the least rainfall were April (196 mm), May (264mm) and June (167mm).  The rest of the months had a range of 304 to 395mm of rain.

 The mean annual temperature is 27.8 C while the annual average maximum temperature is 31.1 C. January is the coolest month with a temperature mean of 23 C. The warmest month is April with monthly average maximum of32.8C Tropical depressions and typhoons frequently occur in the Bicol Region but the number of typhoons hitting the province in nine (9) very 5 years.

Sorsogon Hazard Profile


Sorsogon province is susceptible to both hydro-met and geologic hazards because of its geographical location. The hydro-meteorological hazard includes flooding, rain-induced landslide, and storm surge; geologic hazards include; ground shaking, earthquake-induced landslide, liquefaction/sinkhole, tsunami, and volcanic. Other hazards are red tide and el Niño / la Niña, and at some point of occurrence, all the component city/municipalities are potentially affected.

The table below presents and shows the summary of probable hazards that affect the city/municipalities in the province. It can be noted that Casiguran,

Juban and Sorsogon City have the most number (7) hazards while Casiguran alone is the only town with a sinkhole. Barcelona, Bulusan, Castilla, Gubat, and Matnog had six (6) hazards each; Magallanes, Pilar, and Sta. Magdalena had five (5) hazards each; and the least are the municipalities of Bulan, Donsol, Irosin, and Pto. Diaz has four (4) hazards each. All the city/municipalities are prone to hydro-meteorological hazards, except Irosin a landlocked town emancipated from storm surge.

For geologic hazards, ground shaking is a common threat to all city/municipalities.  Earthquake-induced landslide only the town of Prieto Diaz is not affected considering that there’s not much mountain; Casiguran, Castilla Juban, Pilar, and Sorsogon City are prone to liquefaction; seven (7) municipalities located in the eastern part of the province are at risk to foreign generated tsunami. Barcelona, Bulusan, Casiguran, Gubat, Irosin, and Juban are affected by volcanic hazards. These five (5) municipalities are the perimeter of Bulusan Volcano.

Another related hazard that may affect the socio-economic needs of the people is the occurrence of El Nino/La Nina phenomena and the red tide affecting six (6) municipalities around Sorsogon Bay and Juag Island in Matnog.

The summary of hydro-met hazards per city/municipalities has an area affected varying at any level of susceptibility. Considering the high-level susceptibility to flooding, has a greater area affected compared to other hydro-met hazards. It has an area of about 174.302 square kilometers or 8.78 percent of the provincial total land area.  Storm surge has 9.814 square kilometers or 0.50 percent of the province’s land area.

The summary table also shows the geologic hazard considering the high susceptibility of the area. It can be noted that the town of Bulan is not highly susceptible to any geologic hazard but can moderately be affected. Ground shaking and earthquake-induced landslides potentially affected the area is about 224.22 and 89.882 square kilometers respectively. Liquefaction has a 5.645 square kilometers potential area to be affected or 0.285 percent of the provincial total area.

The tsunami-prone area is those facing the Pacific Coast including the municipalities of Barcelona, Bulusan, Gubat, Matnog, Prieto Diaz, and Sta. Magdalena and Sorsogon City covers an area of about 6.636 square kilometers.

Barcelona Bulusan, Casiguran, Juban, and Irosin are the municipalities directly disrupted by volcanic hazards hence it is the perimeter of the volcano. The area potentially affected by both lahars and lava is about 66.284 square kilometers. Likewise, other affected areas like Bulan, Magallanes, and up to the province of Masbate were affected by ash fall. The ash falls are dependent on the wind direction. Of all the hazard events, the ground shaking has the biggest potential area affected.

Hazard Maps