city planning and development office city of san fernando, pampanga, philippines 1. Natural Features 1.1 Geographic Location The City of San Fernando in Pampanga province forms part, and lies at the core of the Central Luzon great plain. It is bounded in the east by the towns ofMexico and north by Angeles City, in the west by Bacolor and in the south by Sto. Tomas (Figure 5-1. Map of Pampanga). It is approximately 67 kilometers north of Metro Manila. Two (2) critical interregional arterial road connections run through City of San Fernando: The Manila North Road (MNR) a.k.a. MacArthur Highway and the newly rehabilitated North Luzon Expressway (NLEX). These roads link Central Luzon and the Northern Luzon Regions to the National Capital Region. Moreover, an equally important east-west lateral connection i.e. the Gapan-San Fernando- Olongapo Road (GSO) also passes through the City. This road provides lateral access from the China Sea (Subic) to the Pacific Ocean (Baler, Aurora) through its interconnection with the Cagayan Valley road and Cabanatuan - Palayan - Baler Road (Figure 5-2 Major Arterial Roads in Central Luzon). Looking at the regional perspective, the more important crossroads these road networks form i.e. those located at the center or core of Region III, are hosted by City of San Fernando. Because of this, City of San Fernando’s geographic location is its very strategic advantage. This may have been the reason why San Fernando was designated as the Capital town of Pampanga as early as 1904 replacing Bacolor. In addition, it also acts as the regional administrative capital of Central Luzon Region (Region III). 1.2 Topography City of San Fernando’s slope is within the range of 0-3 percent which is characteristically flat. Information shown in Figure 5-3 includes contour intervals (every 10-meter) and slope sections. These elevation sections are: i) North-south slope section (boundary to boundary) and East- west slope section (boundary to boundary). The North-south section starts from Barangay Telabastagan along the MacArthur highway (boundary with Angeles City), passing through Barangay Sindalan, all the way down to GSO road and MacArthur Highway junction, city proper, and finally ending at City of San Fernando-Sto. Tomas boundary. This slope alignment generally follows the alignment of the MacArthur highway. Its east-west section starts from Barangay San Jose to the Poblacion and ends in Barangay San Juan and San Pedro. Note that this slope orientation follows the San Fernando river (SFR). SFR captures its head waters from Mexico, cuts through City of San Fernando before finally draining to the Third River and/or Pasig-Potrero River. As indicated in the Figure 5-3, the northern most part of the city i.e. Angeles-San Fernando boundary mark along the MacArthur Highway has the approximate elevation of 75 meters above mean sea level (MSL). In contrast, Sindalan and MacArthur-GSO road junction have an elevation of 35 meters and 10 meters above MSL, respectively. The city Poblacion and its south-eastern tip at PNR Railroad in Barangay are 3 meters and 1 meter above the MSL, respectively. The aggregate distance between the southern most and the northern most point is about 16 kilometers. If the ratio of rise in elevation and run (distance) is obtained and multiplied by 100 percent, the result will be the slope measured in terms of percentage. The average slope from this orientation is about 0.44%. By all indications, the area is (Figure 5-3) considered extremely flat but will nonetheless allow surface water to flow. In relation with this, there are about six (6) creeks in City of San Fernando one of which originates from Angeles City that follows the north-south drainage orientation. figure 5-3 Slope / Contour Map On the other hand, the east-west lateral section cuts through the Poblacion along the drainage direction of San Fernando River. The elevation proximate to the San Fernando River in the eastern side at Barangay San Felipe along the Mexico border is about 4 meters above MSL. On the other hand, the elevation on the western flank between Barangay San Juan and San Pedro near the Bacolor boundary is about 3 meters above MSL. The distance between this points or boundaries boundary is about 5 kilometers. As such, the slope is about 0.02 percent which is practically flat. These information partly explains the vulnerability of City of San Fernando to flooding specially those areas along the south bank of the GSO where elevation ranged between 1-10 meters above MSL. Matters were made even worse by lahar flows which silted the main drainage channels of Pampanga particularly thePasig-Potrero River and the Third river. Considering San Fernando River is a tributary to these rive systems, its drainage was also greatly affected making the said areas very vulnerable to flooding. 1.4 Climate As shown in the Modified Corona’s System of Climate Classification on Figure 5-4, the City of San Fernando falls under Type I Classification. Areas having Type I climate experience two pronounced seasons, where it is generally dry from December to May and wet from June to November with a maximum rainy period from July to October. This type of climate is generally exposed to the southwest monsoon and gets a fair share of rainfall brought about by the tropical cyclones occurring from July to October. Several meteorological systems or so called natural hazards such as: thunderstorms, cold fronts, inter-tropical convergence zone (ITCZ), easterly wave, tornadoes, monsoons, and tropical cyclones affect the year round distribution of rainfall in the area. The monthly range of temperature is from 20.4ºC to 34.9ºC with an annual average ranging from 22.8º C to 32.1ºC. The warmest temperature recorded was 38.5ºC while the coldest was 15.1ºC. The quantity of water vapor in the air measured in percentage ranges in monthly values from 65% to 84% with an annual of 77%. The principal wind regimes affecting the area are the northeast wind flow from January and February, the southwest wind flow form June to September, and the trade winds. The annual prevailing wind in the area is southwesterly. As shown on the Typhoon Occurrence Map in Figure 5-5, the forecasted number of typhoons for the whole of Central Luzon is 5 typhoons in 3 years or 1.67 cyclones / year as predicted by PAGASA based on historical data. 1.5 Local Drainage and Water Bodies Flat lands offer many advantages but the problem on drainage come along with it. During the height of wet season when the soil has reached its water holding threshold, water infiltration becomes nil resulting to surface run-off. As water seeks its own level moving from higher to lower elevation due to the pull of gravity, it is caught by local drainage systems, then to local creeks, and finally to main river systems. In flat areas (e.g. deltaic planes), the rate by which water is discharged by the rivers to the seas is always slower than the rate it is being supplied by the web of creeks within the watershed during peak of wet season. Thus, flooding consequently follows. This idealized process is true in the case of City of San Fernando. San Fernando River is the biggest and therefore the main drainage channel of the City at least when flood waters are within its carrying capacity. It must be noted that the inherent weaknesses of these river/creek systems to provide adequate drainage is further amplified by other factors which include but not limited to: i) encroachment of right-of-way (illegal and formal settlers), ii) siltation of water channels, iii) lahar flows iv) illegal disposal of garbage, and to certain extent v) urban sprawl or the unplanned and unregulated property development. 1.6 Hydrogeology Based on the Mines and Geosciences Bureau (MGB), the predominant subsoil structure for the whole of Pampanga is Quaternary Alluvium. Alluvium is soil land deposited by a river or other running water. A river is continually picking up and dropping solid particles of rock and dirt from its bed throughout its length. Where the river flow is fast, more particles are picked up than dropped. Where the river flow is slow, more particles are dropped than picked up. Areas where more particles are dropped are called alluvial or flood plains, and the dropped particles are called alluvium. Alluvium is typically made up of a variety of materials. The finer material, or silt, consists of sand and mud. Larger particles, or gravel, are also typically present in a wide range of sizes. In alluvial soils, underground water is abundant which is the case for the City of San Fernando. 2.3 Flood Control and Drainage Around 30 percent of the total land area of City of San Fernando is considered flood prone. As shown in Figure 5-9, these areas are mostly in the poblacion and south of GSO road, and those along major creeks. In August 2004 the entire poblacion was flooded for few days and flooding reached the GSO-MNR junction. This flooding problem is primarily due to silted river channels affected by the eruption of Mt. Pinatubo in 1991. In October of 1995, lahar flow in Pasig- Potrero River covered the town proper of Bacolor and silted all other water channels downstream. If not to timely construction of the MEGA dike by the Department of Public Works and Highways (DPWH), City of San Fernando may have suffered same fate. Fortunately, it did not. However, it was left with perennial flooding problem since those areas it used to drain its flood waters were already of higher elevation.