Location, Area, Boundaries & Political Subdivision

A. Land Characteristics

1. Geographical Location, Boundaries and Land Area

Baguio City is located 251 kilometers north of Manila by road and 41.8 kilometers by air. It is about 5 hours ride by land or 45 minutes by air from Manila . It is landlocked within, the province of Benguet on all sides by its municipalities; on the north by the capital town of La Trinidad , on the east by Itogon, and on the south to west by Tuba. With City Hall as a point of reference, it extends 8.2 kilometers from east to west and 7.2 kilometers from north to south. The City has a perimeter of 30.98 kilometers.

The land area of Baguio as defined by its charter is 48.9 square kilometers. This was however, amended by Republic Act 3092 of the Revised Administrative Code, dated October 10, 1969 which increased the city's land area to 57.49 square kilometers.

2. Geology and Morphology

1. Geologic Features of the City

1. Stratigraphy

Baguio exhibits of young geological and geo-morphological development. It is situated in an elevated terrain, divided by streams with deep gorges and “V” shaped valleys. The city occupies elevations ranging from 1000 to 1500 meters. The city's central plateau is surrounded by hills and wide valleys with deep incised gorges, steep valley ridges at the southern portion and karsted rolling topography at the northern and west -northwest portion of the city.

There are three dominant rock formations in the city. Following are their description and relative ages based on paleonthological dating.

• 1.1   Zigzag Formation - Early Middle Miocene

This rock unit known as the zigzag series was named after the famous zigzag along Kennon road where it typically localizes. The formation generally gives rise to topography of moderate high relief, with landslide surfaces having slaty appearance and lacking of the steep to vertical base scarps characteristics of the klondyke formation.

Rock units belonging to the zigzag formation consist of quartoze wacker and grits, red, and green beds, fossiliferous carbonaceous limestone and conglomerates with predominantly basic clasts.

In the type area along Bued River beside the Lion's head, conglomerates contain horn blende andesite and occasional horn blende-plagioclase plutonic rock clasts. These pass-up into predominantly red, fine-grained sediments interbedded with conglomerates which are often green. They are predominantly graded and show sharp erosive bases. The lower part of the formation is well exposed in the Bued River Southern tributary confluence at Camp 3. It consists of well-rounded cobbles and boulders of basalt, diabase, dasite, mirror gabbro, and pebbles of red chart and epidotized and silified rock in quarts bearing matrix.

1.2   Kennon Limestone - Early Middle Miocene Zigzag formation

This limestone body with its type area at Camp 3, Kennon Road was previously named Kennon Formation. It includes the major limestone bodies found in the area. The watershed limestone is mostly white to cream colored and thick bedded to massive with abundant corals algae. The lower part contains distinctive beds of detrait branching corals with minor interbedded conglomerates and wacker.

1.3   Klondyke Formation - Early Upper Miocene

This rock formation is below Camp 3 along Kennon Road . The formation is broadly folded and occupies syclines forming high ridges. The ridges commonly show deep or vertical base rock scarps within which poorly defined gently dipping beds are visible from a distance.

The formation includes a wide range of lithologies and sedimentary facies, but virtually all are clastic and composed very largely or entirely of andesite material. The predominant lithologies are hornblende andesite conglomerates and boulder beds and they form thick, poorly bedded units with minor grits and wacker and occasionally show cross bedding. The high elevation rock consist of andesitic clastics and interbedded polymic conglomerates with well-rounded clasts of plutonic, volcanic and amphibolitic rocks and silicified and epidotized pebbles in friable weathered matrix. Laminated and sub- horizontal dark tuffs were also observed which are strongly chloritized and superficially resemble a diorite with green chlorite porphyroblasts up to 5 mm diameter in gray green matrix. Grits, wackes and mudstone up to a few meters thick are often interbedded with thick conglomerates and boulder beds, they are commonly purple to gray and sometimes show high angle cross bedding with black magnetite and hornblende rich laminae.

Geologic Structures in the City

1.Folding

The hydrothermally altered Kennon Limestone, klondyke formation are folded as exemplified by a syclinal structure found in Bakakeng and Maryheight areas. The oily remarkable structure feature of the rock units is their nearly horizontal dips in their eastern limits and their general tendency to become steeper in dip towards the west basinward. This indicates a generally rigid upward movement to the Cordillera Central relative to the basin.

2.Active Faults

The active faults, responsible for the seismic activities experienced in the BLLST area during the crustal movement are summarized below.

2.1 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.

2.2 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 regions further northeast. The vertical displacements, measured along the surveyed fault rupture, varied from 0 to a maximum of 1.5 m.

2.3 San Manuel Fault (80 1cm), extending from near Lupao, Nueva Ecija up to Lingayen Gulf . It is predominantly a left lateral strike-slip fault.

Burnham, San Vicente, Loakan, Bued and Tebbo faults. Many other shorted faults are located east of the Loakan Airport . Consequently, the faults could extend beyond the limits shown. These bodies include among others the Limestone formation.

The Mirador, San Vicente, Burnham, Loakan and Bued Faults are 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 .

Among the numerous faults intersecting Baguio City (Mirador, San Vicente, Burnham, Bued and Loakan Faults), only the N45W trending San Vicente Fault exhibited pronounced surface manifestations, such as the landslides at the San Vicente Area and displacements at the Baguio Cemetery.

3.Topography, Slope Aspect and Elevation

Baguio is the highest City in the Philippines . Elevations range from 900 m. along the Bued River to 1600 m. at Pacdal. Majority of the slopes are gentle to moderately steep with a mean slope of 36%. The distribution of slopes, in hectares and percentage terms is shown in the table below. About 1,060 hectares in the city have slopes less than 20%. Areas that are level to nearly level (0-10%) in Baguio occupy about 20 hectares.

The topographic features of the area exhibit the rugged topography of the cordilleras. The variety of natural landforms in the city with its pine covering makes the city's landscape interesting and scenic. Many summits offer panoramic vistas and views to near and distant place around the city.

Table 2E-1. Distribution of Slopes, Baguio City

4. Soils

There are three (3) main types of soil in the study area: 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.

Table 2E-2. T pica! Profile Diagram of Tacdian Loam.

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.

Table 2E-3. Typical Profile Diagram of Bakakeng Sandy Clay Loam

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.

Table 2E-4. Drainage of Soil Types

Rough mountainous lands are to be found in the northwestern part of the study area. They can also be found in the south, at the Kennon gorge. These lands are very rough and irregular and maybe best utilize for wildlife, forest, and watershed. Examples of these cliffs whose slopes sometimes approach 100 percent are found along Asin, Tuba, Kennon, and Naguilian Roads.

In general, soils within the area 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.

5. Land Uses

a. Existing Land Uses

From the total land area of Baguio City that is pegged at 57.49 square kilometers, residential area occupies 2,102.6 hectares or 36.57 percent Most of these are in the form of single detached semi-concrete type. These are mostly concentrated near business activities and service centers within 4 to 5 kilometers radius from the Central Business District (CBD). First class subdivisions classified under PD 957 are mostly located in areas accessible to the CBD. Middle class subdivisions classified under BP 220 are likewise found at the western and southern portion of the city. High-density housing is generally located on the part

A study of the BUST Urban Planning Project conducted in 1994 reveals that squatters as gleaned from the table below occupy 247 hectares or 5 percent of the city.

Table 2E-5. Areas occupied by squatters, 1994

Commercial areas now occupy 201.35 hectares or 3.5 percent of the total land area that are concentrated at the CBD and tend to develop towards existing major roads. Small home occupation such as sari san store, beauty parlor, bakery, dressmaking and the like are located within residential sites in the 129 Barangays.

There are 347.52 hectares being occupied for institutional purposes. These include schools, churches, hospitals, and government institutions and are scattered in various locations within and outside the CBD.

Parks use up 51.42 hectares of the city's land area. These are the Botanical Garden, Burnham, Sunshine, Igorot. Wright, Mines View, Lion's and mini parks and golf course at Country Club.

Industrial areas occupy 130.39 hectares. These are the Philippine Export Processing Zone (PEZA) and the Irisan Lime Kiln being managed by the Benguet Corporation. Open areas covering 1,951.8 hectares are vacant/idle areas but which are titled properties private ownership. Some have steep slopes with slopes greater than 50 percent that are unbuildable. There are several parcels of vacant land that have been plotted from 1993 aerial photography conducted for the BUST Urban Planning Project

Table 2E-6. Existing Land Use Plan of Baguio

Data Source: Proposed Comprehensive Land Use Plan of Baguio , 2000

There are over 50 proclamations and other issuances declaring certain areas in Baguio as reservations for a number of public purposes. They occupy about 951.5 hectares or more than 16 percent of the total land area of Baguio City . Furthermore the whole of the city of Baguio has been declared as Town Site Reservation and applications for land ownership within this area as Town Site Applications.

The largest land holding is Camp John Hay (677 Ha.), and there are number of other holdings reserved by presidential decree for military, institutional or open spaces. In all approximately 16 percent of the city of Baguio is reserved.

Table 2E-7. Public Reservations

Many of these reservations have become the location of squatting activities resulting to the diminution of land areas specifically reserved for its intended purposes.

b. Ancestral Claims

The Community Environment and Natural Resources Office in Baguio City received a total of 785 claims covering a land area of 9422.9 hectares. With the total land area of Baguio pegged at 5749 hectares, it can only be inferred that many of the claims are overlapping and conflicting. Camp John Hay alone has so claimants, flue Philippine Military Academy with 10, the Bureau of Animal Industry with 5, Teacher Camp 2 and Navy Base with 3.

c. Proposed Land Uses

With the meager land resources that the city has, the proposed land use plan seeks rationalize the allocation of land into appropriate land uses. It is also viewed to govern the orderly development of land through the implementation of a sound physical planning and appropriate land use controls to preserve its natural resources including its scenic amenities.

It has also identified node areas where growth will be encouraged and thus seek to decentralize activities from the Central Business District.

The updated land use plan presents the major land uses that are suitable for the city's development, i.e. residential, commercial, industrial, institutional, parks, open areas and government reserves. The plan was prepared in consideration with the city's critical environmental factors. This includes the topographic and soil conditions, hydrologic variables, and ground vulnerability.

6. Natural Disasters

Residents as welt as visitors single out the temperate climate and the intrinsic beauty of the landscape of the city as its major attractions, Continuous increase in population over the years has evolved a very critical environment. Thus, the historic vocation of the city, that of a mountain resorts, continues to be jeopardized. Certain basic causes can be identified in the deterioration of the city's environment, like the fast rate of population growth that pushed human settlements to high-risk areas, lack of consideration on the importance of site solution and design for residential developments, the general lack of understanding on vegetation, soil, terrain, rocks, drainage channels and streams as natural resource with varying ecological, aesthetic conservation, and safety implications for urban d faulty land use prescriptions and land utilization poses hazard to the safety of residents.

The rugged topography and critical environment of the city have limited its capacity to accommodate rapid urbanization. Urban sprawl is widespread without regard for seismic and geologic hazard and the city's capability to provide adequate water. All these continue to adversely affect the city's high aesthetic value.

The presence of several faults and lineaments in the City is aggravated by continuing denudation of its vegetative cover results 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 occur from several centimeters to hundreds of meters in area dimension. It vanes from soil to rock fall where huge boulders fell from steep slopes.

Baguio is periodically visited by earthquake. Temblors and tremors induced many of the present slides. Most of these mass movements occur in unstable slopes while some can be attributed to ground shaking and surface faulting and non-uniformed movement of rock blocks along lines of weaknesses. Landslides are likely to occur in faulted zones, where unstable slope is dominant in the formations (Klondyke and Zigzag). The July 16, 1990 earthquake resulted to an over abundance of landslides that caused numerous deaths and massive destruction of properties. These losses could have been mitigated or minimized by engineering and geologic investigation or by a hazard assessment and zonation of the City.

Rain induced mass movement occurs during heavy rains. Man-made factors are highly contributory to this type of mass movement. The demand for housing due to a rapidly increasing population resulted to uncontrolled land development, i.e. excavations, and settlement along unstable slopes and the dissipation of the vegetative cover leaves the soil exposed to over saturation that ultimately results to erosion and landslides. These natural processes led to the alteration of city's natural drainage system. On the other hand, the drainage system established in the developed areas is now very inadequate due to clogging. Many spoil banks slides are attributed to the changes in the drainage system due to road and building/house constructions. Considering Baguio 's high relief and steep slopes, water discharge travel fast and with improper drainage this will scour road banks, residential areas with steep and unstable slopes resulting to the weakening of base.

The aftermath of typhoon Feria caused the death of 38 persons and damages to properties mounting to more or less 325 Million due to landslide/erosion and flooding. As reported, 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 dissolve as a result of weathering due to exposure to running water. According to the Bureau of Mines there are four (4) major sinkholes in City, namely; City Camp Proper, Crystal Cave , Dominican and Green Valley with diameters ranging from 1 meter to 225 meters wide. These areas are classified as high-risk areas. The exposure of the underground streams through karst windows may result in time due to gradual caving. Primarily, the failure or collapse of the roof or crown pillars that could induce surface ground subsistence and sinkhole formation particularly in areas above caverns and galleries where roof/crown pillars are not strong enough may not support the overlying load.

Moreover, some residential houses are located near or on drainage areas thereby posing hazard to lives and properties. This situation necessitates the preparation of a detailed geological underground and surface mapping of the entire city that will guide the local government prepare the necessary mitigating policies and measures that will guide legislators and executives in their decision-making processes.
 

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