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Physical Characteristics

This page describes the physical features of Central Visayas and of the four provinces comprising the region. Specifically, it describes the region?s location relative to the other islands within the Philippine archipelago; it?s land area, topography, climate, soil characteristics and state of its environment and natural resources.

Location and Land Area

The Central Visayas Region (Region 7) lies at the center of the Philippine archipelago between the major islands of Luzon and Mindanao. It is bounded on the north by the Visayan Sea; on the east by the Camotes Sea and the Camigao Channel; on the south by the Mindanao Sea; and on the west by the province of Negros Occidental.

Figure 1
Location of Central Visayas

 

Four island provinces compose the region; Bohol, Cebu, Negros Oriental, and Siquijor. Bohol Strait and Ta?on Strait separate the four provinces.

Region 7 is the second smallest region in the country with a total land area of 14,951.5 square kilometers. This constitutes 5 percent of the country?s land area. Negros Oriental accounts for the largest share of the regional land (36%), followed by Cebu (34%), Bohol (28%) and Siquijor (2%).

Table 1
Land Area and Political Subdivisions
Province Land Area(sq. km.)1 No. of Districts No. of Municipalities No. of Cities
Bohol 4,117.3 3 47 1
Cebu 5,088.4 8 47 62
Negros Oriental 5,402.3 3 20 53
Siquijor 343.5 1 6 0
Central Visayas 14,951.5 15 120 12
1.) Source: 1999 Philippine Statistical Yearbook
2.) The municipality of Talisay was converted into a component city per RA 8979 approved on 23 November 2000
3.) The municipalities of Bayawan and Tanjay were converted into component cities per RA 8993 (approved on 05 December 2000) and RA 9026 (approved on 05 March 2001), respectively.

Topography
 With the exception of Bohol, the topography of Central Visayas is rugged. It is characterized by highlands dominating the interior portion of the provinces and narrow strips of arable land lining the coast. Of the region?s total land area, the hilly to mountainous areas constitute about 62 percent and the level to rolling areas account for the remaining 38 percent.

Table 2
Area by Slope Range By Province
(in square kilometers)

Central Visayas
Slope Range(%) Description Area % To Total Area
0-3 Level to nearly
level		 2,431.07 16.26
3-8 Gently sloping to
undulating		 1,140.80 7.63
8-18 Undulating to
rolling		 2,108.95 14.11
18-30 Rolling to
moderately steep		 3,304.01 22.10
30-50 Steep hills
and mountains		 3,045.47 20.37
Above 50 Very steep hills
and mountains		 2,921.12 19.54
  TOTAL 14,951 100


Bohol
Slope Range(%) Description Area % To Total Area
0-3 Level to nearly
level		 712.85 17.31
3-8 Gently sloping to
undulating		 375.19 9.11
8-18 Undulating to
rolling		 849.02 20.62
18-30 Rolling to
moderately steep		 624.73 15.17
30-50 Steep hills
and mountains		 895.07 21.74
Above 50 Very steep hills
and mountains		 660.40 16.04
  TOTAL 4,117.26 100


Cebu
Slope Range(%) Description Area % To Total Area
0-3 Level to nearly
level		 925.04 18.18
3-8 Gently sloping to
undulating		 233.90 4.60
8-18 Undulating to
rolling		 409.49 8.05
18-30 Rolling to
moderately steep		 841.79 16.54
30-50 Steep hills
and mountains		 1,328.18 26.10
Above 50 Very steep hills
and mountains		 1,349.99 26.53
  TOTAL 5,088.39 100


Negros Oriental
Slope Range(%) Description Area % To Total Area
0-3 Level to nearly
level		 744.39 13.78
3-8 Gently sloping to
undulating		 464.46 8.60
8-18 Undulating to
rolling		 811.05 15.01
18-30 Rolling to
moderately steep		 1,712.42 31.70
30-50 Steep hills
and mountains		 664.81 12.31
Above 50 Very steep hills
and mountains		 1,005.14 18.60
  TOTAL 5,402.27 100


Siquijor
Slope Range(%) Description Area % To Total Area
0-3 Level to nearly
level		 48.79 14.20
3-8 Gently sloping to
undulating		 67.25 19.58
8-18 Undulating to
rolling		 39.39 11.47
18-30 Rolling to
moderately steep		 125.07 36.41
30-50 Steep hills
and mountains		 33.06 9.62
Above 50 Very steep hills
and mountains		 29.94 8.72
  TOTAL 343.40 100

Sources : BSWM. Regional Land Use Assessment, 1992;
Siquijor PPFP, 1995


 Bohol is generally flat with the level to rolling lands accounting for 47 percent of the province?s total land area. It has vast agricultural lands, mostly found in the interior portion of the province. Cebu, on the other hand, is rugged and mountainous with low peaks forming a mountain range from north to south at the center of the island. Negros Oriental and Siquijor, for their parts, are mostly hilly and mountainous like Cebu. Volcanic peaks, hills and occasional plateaus dot the interior of Negros Oriental. In Siquijor, its highest point is situated in Mount Bandilaan, which has an elevation of 557 meters.

Climate

Under the Corona Classification System, which is based on the seasonal distribution of rainfall, the areas of the region have the following types of climate:

Type I. This is characterized by two pronounced seasons with maximum rain period occurring from June to September. The dry season lasts from three to six or seven months. This type of climate is peculiar to the southern part of Negros Oriental which is open to the southwest monsoon.

Type III. This climate type has no pronounced maximum rain period, with a short dry period lasting from one to three months. This climate is prevalent in the northern half of Negros Oriental, the southern half of Cebu and the whole of Siquijor.

Type IV. Under this type, rainfall is more or less evenly distributed throughout the year. Bohol and the northern part of Cebu have this type of climate.

Mean Annual Temperature. The mean annual temperature in the region is 27 degrees Celsius. Average temperature readings at various stations are as follows: 27.5 degrees Celsius in Cebu; 27.9 degrees Celsius in Dumaguete, Negros Oriental and 27.8 degrees Celsius in Tagbilaran, Bohol. The hottest months are February, March and April and the coldest is January.

Relative Humidity. The region?s relative humidity (RH) is 82 percent. The lowest mean RH of Cebu is 75 percent. Bohol?s lowest mean RH is 76.6 percent and that of Negros Oriental and Siquijor is 78 percent.
Wind Velocity. From November to May, the wind blows in a northeasterly direction at an average velocity of 11 kilometers per hour. From June to October the southwesterly winds prevail at an average velocity of 7 kilometers per hour.


Soil Characteristics
 Most of the region?s soil are of the clay group. Clay soil is of fine texture; hence, it has the ability to retain high amounts of water and store plant nutrients on the surface. Soil of this type is suited for agriculture. Clay however becomes very hard when dry and sticky when wet. Tillage, therefore, becomes difficult at extremely high and low levels of moisture. Its low internal friction (shearing) character makes clay soil unsuitable foundation for tall buildings and heavy infrastructure. Its high permeability and capillarity characteristics are also disadvantageous because these allow easy seepage of the contaminants and pollutants to the groundwater.

Environment and Natural Resources
Pressures of a large growing population, over utilization and resource use conflicts have affected the natural resource base of Central Visayas. The state of the region?s environment is discussed below by ecosystem.

Land Resources and Agricultural Ecosystem. Central Visayas, which has a total land area of 1.5 million hectares, is one of the most densely populated regions in the country. Its man-land ratio is 4 persons to a hectare. This is higher than the national average of 2 persons to a hectare. The demand for land for residential use is rising particularly in urban centers. Land development in Metro Cebu, for example, is already encroaching on protected watersheds. Preliminary data from the Bureau of Soils and Water Management (BSWM) indicated that agricultural land resources in the region declined by an average of 2,997 hectares per year from 1980 to 1992. Loss of fertile topsoil especially in the upland areas is a major problem confronting the region. BSWM reports that 88 percent of the region?s land resources is experiencing varied levels of erosion, making it one of the most eroded regions in the country. Of the total land area suffering from erosion, 22 percent is severely eroded; 38 percent is moderately eroded, and 25 percent is slightly eroded. Meanwhile, indiscriminate conversion of prime agricultural lands to non-agricultural uses has gone unchecked as industrial and other commercial establishments are now expanding to areas outside the cities.

Urban Ecosystem. The urban ecosystem in the region is plagued by problems of mounting garbage, air and water pollution and congestion. Waste disposal is one major concern of all provinces. In Cebu, only Cebu City has a landfill site. Its plan to operate an incinerator meanwhile was met with public resistance. The Department of Environment and Natural Resources (DENR), for its part, has completed studies on waste disposal sites in all provinces. There are now efforts to address the issue of toxic and hazardous waste management. These efforts are however stymied by the absence of a sewerage management system in the region. This has resulted to the pollution of waterways, rivers, and coastal waters. The extent of the deterioration of air quality cannot be monitored regularly because of lack of equipment. Nonetheless, the increase in the number of motor vehicles and manufacturing plants has, for sure, contributed to the increase in the amount of suspended particulates, lead, nitrogen oxides and other noxious gases in the air.

Hydrology and Freshwater Ecosystem. Surface and groundwater are the sources of water for domestic and industrial use in Central Visayas. The region has 19 major rivers, which serve as main drainage for water run-offs. Of these, 9 are found in Negros Oriental, 5 in Bohol, and 5 in Cebu. Siquijor has no major river system but has 5 minor rivers. The 19 major rivers have a combined drainage area of 4,692 square kilometers. Inabanga and Loboc Rivers, both in Bohol, have the largest drainage area at 572 square kilometers and 513 square kilometers, respectively. These 19 rivers are capable of supplying an estimated 519.83 million cubic meters of water annually. Lakes, dams and reservoirs also serve as catchments for surface run-offs. These are potential sources of water for irrigation, domestic and industrial use. These bodies of water occupy about 1,023 hectares in the region. The region?s groundwater storage is estimated at 2,053 million cubic meters per year. Despite efforts of the Natural Water Resources Council (NWRC) to monitor ground water development, data on the number of wells constructed are not accurate. An inventory of wells in 1988 showed that a total of 11,230 wells were drilled. The bulk or 86 percent (9,713 wells) were of the level I type, 11 percent were level II and 3 percent were level III. The need to ensure sufficient water supply instigated the proclamation of the upland areas as watershed reservations. Protection of these areas is however hampered by the presence of speculators and developers who have bought properties within these protected areas. There is in fact a growing public clamor for titling of alienable and disposable lands in reservations. Sections of rivers that traverse Metro Cebu are mostly biologically dead. Indiscriminate dumping of domestic and industrial waste has not been adequately addressed. Data on water quality of the region?s rivers show disturbingly high BOD concentrations. In some instances, these were higher than acceptable levels of toxic substances. The most polluted river in the region is the Butuanon River in Mandaue City, Cebu. Metro Cebu has urgent problems with saltwater intrusion in its groundwater tables. This is brought about by loss of vegetative cover in the uplands, decreasing recharge areas of the aquifers due to uncontrolled urbanization and increased land development activities in the uplands which affected the lowlands, and over extraction of groundwater. The cities of Tagbilaran, Dumaguete and the province of Siquijor, as well as a number of smaller islands around the region report similar water-related problems ranging from pollution to saltwater intrusion.

Coastal and Marine Ecosystems. Excessive fishing and an open access regime have resulted in overexploitation of the region?s fishery resources. Studies indicate that the region?s marine waters are overfished and that the quality and productivity of coastal ecosystems are seriously impaired by years of destructive use. Driven by stiff competition, fisherfolk resort to illegal and destructive means of fish capture. A study in Olango Island shows that fish catch per fisherman has declined from 20 kilograms before 1970 to only 2 kilograms in 1998. The deterioration of the uplands has affected the coastal zone resulting in siltation, habitat destruction, pollution, and loss of marine biodiversity. No wonder, thus, that the communities depending on fishing for livelihood are generally poor. Government?s conflicting policy on whether or not to preserve the remaining mangrove forests is reflected in the way fishpond development is allowed. Fishpond development has been tagged as the major cause of the shrinking of mangrove forests in the region. There is a controversy in foreshore land claims. Extensive areas of foreshores and beaches are also being damaged and spoiled by uncontrolled development by speculators. Even if the foreshore has been applied for development, control by the local government unit (LGU), DENR and the Department of Public Works and Highways (DPWH) of activities undertaken in the area is difficult because of the pressure to develop due to the tourism potential of foreshore areas. The developments included reclamation and beach resort construction. In addition, landless people are drawn to the beaches where shanties are easily built. Foreshore land claim controversies are most pronounced in Cordova and Lapu-lapu in Mactan Island, and in Talisay City.

Forest Ecosystem. The region?s forest resource is dwindling. Satellite data in 1988 showed that only 5 percent of the region?s total land area had forest cover. This translates to roughly 43,000 hectares of second growth forests. What is left of the primary forest near PNOC?s main geothermal 10-km radius area of responsibility (critical area) totals around 4,096 hectares.