Chapter II GEO- PHYSICAL ENVIRONMENT

Baguio City Ecological Profile 2018

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Chapter II GEO- PHYSICAL ENVIRONMENT

LOCATION AND AREA

Baguio City is geographically located in the south central part of Benguet Province in the

Cordillera Administrative Region (CAR). The developed portion of the city corresponds to a plateau that rises to an elevation of 1,400 meters. Total land area is 57.49 square kilometers enclosed in a perimeter of 30.6 kilometers.

Approximately, the city is 250 kilometers north of Manila.

POLITICAL BOUNDARIES

Map 1: Location Map of Baguio City


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TOPOGRAPHY

Elevation ranges from 900 meters along the Bued River to 1,600 meters at Pacdal.

Majority of the slopes (about 78% of total area) are gentle to moderately steep with slope

of less than 30%. Only about 22% of city’s land area has steep slopes greater than 30%

Table 1 : Slope Categories, Baguio City DESCRIPTION

SLOPE GRADE

AREA (HAS.)

PERCENT

Level to gently sloping 0- 8% 1,530.78 26.63

Gently sloping to undulating 9- 18% 955.58 16.62

Undulating to moderately steep 19- 30% 2,011.50 34.99

Moderately steep to steep 31- 50% 785.18 13.65

Very Steep >50% 465.96 8.11

Total 5,749.00 100.00


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Map 2: Slope Map

GEOLOGY

ZIGZAG FORMATION

This is a sequence of Late Oligocene to Early Miocene conglomerates, sandstones and shales, in places with limestone lenses uncomformably resting on top of the Pugo Formation. A portion of this sedimentary sequence is intruded by quartz diorite porphyry, producing mineralized skarns and marbles. The Halfway Creek Formation (UNDP, 1987) and Camp Three Beds (Mitchell & Leach, 1991) were regarded as part of Zigzag Formation. Among the formations in the area, this unit is considered to have the highest potential for groundwater.

KENNON FORMATION

This Middle Miocene formation unconformably overlies the Zigzag formation and rests below the Klondyke Formation. It consists principally of massive to buff gray biohermal limestone with associated calcarenites and calcirudites. The basal portion consists of wackes, including a conglomeratic calcarenite which contains clasts of volcanic rocks, diorite pebbles and cobbles. Lenses of sandstones and siltstones up to 0.3 m thick have been observed in the middle section. Mirador Limestone is considered here as part of Kennon Formation (S. David). For groundwater resources, the Kennon Formation is deemed to have more moderate potential.


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KLONDYKE FORMATION

This is a thick sequence of Middle Miocene to early late Miocene clastic sedimentary rocks consisting mainly of polymictic conglomerates with interbedded sandstones, siltstones, shales and in places intercalated with flow breccias and pyroclastic rocks. It rests unconformably over the Kennon Limestone and underlies wide areas of the western sides of Baguio City Quadrangle and exposed at higher elevation. Different authors give different thickness. Balce et al (1980) gave an estimate of 1,798 meters for the Kennon Road section but admit it might be higher in other places. Durkee and Pederson (1961) estimated the thickness in this section to be 2,820 m. De Leon, et al (1990) gave an estimate of 3,500 m. for Marcos Highway section of the formation. Valley areas overlying this formation may yield small quantities of groundwater but most parts have poor groundwater potential (Quema, 1971). Monzon (1991) meanwhile, reported the presence of saturated zone in the conglomerates, limestone and sandstone in the area. Based on these observations, this study considered the Klondyke formation as having moderate potential for the groundwater availability.

BLACK MOUNTAIN QUARTZ DIORITE PORPHYRY

This is typified by the quartz diorite porphyry which hosted copper deposits and other mineralization in the district. It is differentiated from the CCD by its porphyric texture and younger age (Late Miocene). Like the CCD however, this rock unit has low potential for groundwater availability.

SOILS

There are three (3) main types of soil : Bakakeng Sandy Clay Loam, Mirador Clay Loam, and Tacdian Loam. Almost half of the study area is covered by the Bakakeng Sandy Loam, which incidentally is the second largest soil group in southern Benguet. It cuts across the area from the north to southeast and extends eastward to Itogon. Mirador Clay Loam is found in the southwestern part of the study area. The smallest soil group, Tacdian Loam, lies in the mid-north of the area. The physical characteristic of these soils types; their structure, consistency, and texture per horizon can be seen in the table below.

Of the three- (3) soil types, Tacdian has the thinnest surface soil, being 5 to 10 centimeters from the surface. Cultivation of this type of soil along steep slopes may, without adequate control of surface run-off, result to its erosion down slope. Bakakeng Sandy Clay Loam and Mirador Clay Loam have thicker topsoil. If however, they are cultivated along steep slopes, and no adequate measures are undertaken to control slope erosion, the topsoil will gradually be washed away by running water. This eventually exposes the subsoil, which is unproductive for plant growth. The external drainage of these soils is of the utmost importance. The terrain where these soils are located can be best described as moderately steep to very steep. Without adequate measures to regulate drainage’s, these soils will be excessively drained, thus resulting to massive erosion. In general, soils within the city are classified as clay loam. Soil materials for embankment or fill purposes can be found in almost any place in the area. Most of the hillsides can be tapped to yield unlimited materials for construction purposes.


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RIVER SYSTEM

The city is criss crossed by several rivers among which are the Bued, Balili, Galiano– Camp-Asin, Naguilian Rivers and Ambalanga. The widest river is the Bued River followed by the Balili River.

DRAINAGE SYSTEM Surface water drains through the rivers; 1) to the east is the Ambalanga which follows a southeasterly to easterly course and drains into the Agno River, 2) to the north is Balili River, which follows a general northerly course and converges with the Bauang River basin to the north-northwest, 3) to the west is the Galiano River which drains into the Aringay River; and 4) to the south is the Bued River which drains into the Patalan River and the Lingayen Gulf. Drainage facility at the Central Business District is through an underground drainage system along Magsaysay Avenue constructed by the Department of Public Works and Highways and drains towards the Balili River.

LAND RESOURCES

EXISTING LAND USE AND LAND USE TRENDS Residential area (56.35 percent) occupies the largest land use and is therefore the most

dominant among all the urban uses.

Commercial areas occupy some 317.13 hectares or approximately 5.52 percent of the

City’s total land area. These are found mostly at the Central Business District and along

major thorough fares in the City like Magsaysay Avenue, Bokawkan Road, Naguilian

Road, Marcos Highway and Kennon Road. Various private and public institutions operating in the City take up some 233.57 hectares (4.07 percent). These institutions include schools, hospitals, churches, military reservations, and government facilities. Among the military reservations are the Philippine Military Academy, Navy Base and Camp Allen. A. Planned Unit Development Zone takes up a small portion of the City’s land at only 57.89 hectares or 1.01 percent. The Philippine Export Zone Authority in Loakan is the largest industrial estate in the Baguio and is home to multi-national companies like Texas Instruments, Moog Controls Corporation. B.

Table 2 : Existing Land Use Categories

Land Use

Existing Land Area (Hectares)

Percent

R1 - Low Density Residential Zone 1,395.21 24.27

R2 - Medium Density Residential Zone 610.26 10.61

R3 - High Density Residential Zone 1,234.44 21.47

C1 - Low Density Commercial Zone 147.62 2.57

C2 - Medium Density Commercial Zone 96.62 1.68

C3 - High Density Commercial Zone 72.89 1.27


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Land Use

Existing Land Area (Hectares)

Percent

Camp John Hay-Planned Unit Development Zone (Special Tourism Economic Zone) 301.86 5.25

Camp John Hay-Watershed / Protected Forest Zone (Reservation) 323.55 5.63

Planned Unit Development Zone 57.89 1.01

General Institutional Zone 233.57 4.07

Parks and Recreation Zone 60.80 1.05

Watershed/Protected Forest Zone 240.37 4.18

Vacant Forested Areas 591.84 10.29

Slaughterhouse Zone 2.70 0.05

Cemeteries/Memorial Parks Zone 13.88 0.24

Airport Zone 32.16 0.56

Utilities Zone 9.85 0.17

Special Use (Bureau of Plant Industry) 8.98 0.16

Special Use (Bureau of Animal Industry) 104.35 1.81

Roads/Roads right-of-way 210.16 3.66

Total 5,749.00 100.00

Though already dwindling, pockets of pine forested areas remain visible in the City’s

landscape. The remaining forested area accounts for about 4.18 percent of the total land area. Pine forests are found mostly at the outskirts of the City, close to the City boundary.

Table 3 : List of Watershed/ Protected Forest Zone

Source: DENR-Forest Management Services.

PARTICULARS

AREAS IN HECTARE (HA)

1. Busol Forest Reserve (Baguio Side) 112.00

2. Buyog Forest Reserve 21.93

3. Camp 8 27.50

4. Crystal Cave 4.07

5. Forbes Park 1 29.85



8. Lucnab 5.98

9. Pucsusan 0.95

TOTAL 240.37


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Map 3: Existing Land Use


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CLIMATE Baguio City is known for its cool climate. On the average, Baguio is eight (8) degrees cooler than any place in the lowlands. In January 18, 1961, Baguio experienced the lowest temperature at 6.27 degrees centigrade.

The city’s climatic type falls under Type 1. The rainy season is from June to October. It gets the biggest amount of rainfall in the country, twice the volume of rainfall as compared to Manila. The record for the heaviest volume of rainfall occurred in Baguio in July 1927 when it measured 4.77 meters while November to May is the dry season.

NATURAL HAZARDS/ CONSTRAINTS

FLOOD PRONE AREAS Some areas in the city experience flooding specifically portions within barangays: Lower Rock Quarry, City Camp Proper, Guisad Surong, Irisan, Lourdes Subdivision Extension and City Camp Central.

Map 4: Flood Prone Areas Map


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Map 5: Drainage Map

FAULTS The faults, contributing for the seismic activities experienced in the BLISTT area during the crustal movement.

EARTHQUAKE GENERATORS SURROUNDING BAGUIO CITY Segments of the Philippine Fault - extending from Laoag in the north to Mindanao in the South (1,600 Km long). The fault in Luzon divides the mountainous Central Cordillera from the lowlands of the Central Valley Basin in the South. Three Earthquakes occurred in 1937, 1973 and 1975 that resulted to left lateral movements of the fault. Eight similar strong earthquakes that happened in 1893, 1902, 1922, 1924, 1937, 1941, 1947 and 1948 had their epicenters along or very near this fault zone. Digdig Fault - is a branch of the Philippine Fault, extending from Dingalan Bay, and turning northwards near Santa Fe/San Quintin, passing Baguio City at about 40 km to east. Prior to the July 16, 1990 earthquake, documented evidence reveals movement of the digdig fault. There were two (2) earthquakes that occurred on July 16, 1990. Initially the epicenter was located at 13 Km NNE of Cabanatuan City or about 90 Km SSE of Baguio while the other occurred 20 Km east of Baguio. The horizontal crustal shift, along the surveyed 135 km long inferred fault rupture, exceeded 3 m, with 6.2 m as the largest displacement measured so far. Larger displacements may have occurred in the unexplored mountain


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regions further northeast. The vertical displacements, measured along the surveyed fault rupture, varied from 0 to a maximum of 1.5 m. San Manuel Fault (80 km) - extending from near Lupao, Nueva Ecija up to Lingayen Gulf. It is predominantly a left lateral strike-slip fault. Tebbo Fault (70 km) – located approximately 10 km. southeast of Baguio City. Tuba – west of Baguio City. Approximately 5 km away with shortest 50 km long, NW trending. LOCAL FAULTS Although they are not active faults, the Mirador, San Vicente, Burnham, Loakan and Bued Faults are local faults traversing through the built-up areas of Baguio City. Among the numerous faults intersecting the city (Mirador, San Vicente, Burnham, Bued and Loakan faults) only the N45W trending San Vicente Fault exhibited pronounced surface manifestations, such as landslides at the San Vicente area and displacements at the Baguio Cemetery. These are zones of weaknesses with thicker soil cover, highly fractured rocks; where energy is released during earthquake therefore causing amplified ground shaking.

Map 6: Local Fault line Map


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GEOLOGIC HAZARD The presence of several faults and lineaments in the City is aggravated by continuing denudation of its vegetative cover resulting to soil exposure. The remaining vegetative cover, mostly cogon or grass serves as replacements and can only protect a thin layer of soil that are very susceptible to erosion and downgrading process. There are two types of mass movement prevailing in the city, earthquake induced, and rain induced erosions. Landslides varies from soil to rock fall where huge boulders fall from steep slopes.

Map 7: Geologic Map

Table 4 : Landslide Susceptibility, Baguio City

LEVEL Area in sq.km

% share Description

High Landslide Susceptibility and Critical Area 5.96 20.01

Unstable areas a significant portion is affected by mass movements

High Landslide Susceptibility 17.60 59.08 Unstable areas, highly susceptible to mass movements

Moderate Landslide Susceptibility 5.60 18.80 Stable areas with occasional and localized mass movement

Low Landslide Susceptibility 0.63 2.11 Stable areas with no identified landslide

Total Areas Mapped 29.79 100.00 Source of Basic Data: MGB-CAR

Of the almost 30 hectares mapped, 60% or about 18 hectares have unstable areas

while only 2 % or less than one hectare has low landslide susceptibility. Areas with high


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landslide susceptibility are considered unstable areas with highly susceptible mass movements.

Map 8: Landslide Susceptibility

Map 9 : Sinkholes Map


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Part of Baguio lies atop a limestone formation, which explains the numerous sinkholes underneath some parts of the City. Sinkholes develop when the limestone formation is dissolved as a result of weathering due to exposure to running water. There are four (4) major sinkholes in City, namely; City Camp Proper, Crystal Cave, Dominican and Green Valley based on the data gathered at the Mines and Geosciences Bureau.

Chapter II GEO- PHYSICAL ENVIRONMENT

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