Geoenvironmental Monitoring of the Lingayen Gulf, Northwestern Luzon, Philippines Using Remote Sensing Technology
Abstract
The Lingayen Gulf area in northwestern Luzon is part of the Philippine northern Luzon Growth Quadrangle. The area is characterized by rapid population growth and expansion of urban centers. This growth changes the landcover and puts a strain on the available resources of the area.
At the same time, the area's geoenvironmental condition is changing. The 1990 Luzon earthquake caused slope failures and hastened the sediment erosion process. These sediments eventually find their way into the Lingayen Gulf. The earthquake also induced liquefaction particularly in Dagupan area. The 1991 Mt. Pinatubo eruption contributed sediments that will also find their way into the gulf.
Several satellite images from 1972 to 1994 were acquired over the Lingayen Gulf area. These images provide the basic information on the geoenvironmental condition of the Gulf area for about 22 years. These will also be an input into the region's development plan.
Regional geological interpretation was made on the Landsat TM and JERS-1 images to determine the geological and geomorphological boundaries and lineament zones, chronological changes in the coastal topography and the distribution of coral reefs and mangrovels.
The image documented a regression of about 200 meters along the coastline of Ago, la union and transgression along other parts of the coast. The dispersion pattern of turbid waters was shown. Slope failures in northern Luzon have increased in recent years. Sedimentation of river systems also increased. Mangrove areas are being transformed into fishpond areas.
1.0 Introduction
The Lingayen Gulf area in northwestern Luzon is part of the Philippine Northern Luzon Growth Quadrangle. This Growth Quadrangle, or Northquad for short, is envisioned to become a leading economic zone, which is market-powered and a source of entrepreneurial energy (Batino, 1996).
This area is characterized by rapid population growth and expansion of urban centers. The 1980 data on population densities in the Philippines shows that the Lingayen Gulf area has >300 inhabitants per km
2. This value is similar to that in Metro Manila and Cebu. However, please note that the population in the gulf area is expectedly lower than in Metro Manila or Cebu. This growth pushed the land values higher. For example, commercial can run as high as P12,000 per sq. m in La Union and as low as P120 per sq.m Pangasinan. Similarly, residential lots can go to a high of P7,250 per sq. m. in La Union (Batino, 1996).
The growth occurring in the gulf area changes the landcover and puts a strain on the available resources of the area. Already, several resorts and a cement plant are operating in the area (Domingo and Javalosa, 1996). Several mining firms are operating in the Bagulo Miiral District (BMD) to the northeast. One of the latest locators in Malaysia's national car manufacturer, Proton Wira, which chose Mabini, Pangasinan as the site of its assembly plant. Several other complementary industries like auto components and parts are also planning to set up shops in nearby areas (Batino, 1996). These developments has contributed, in one way or another, to the environmental problem in the Gulf area. These major problems are sedimentation, destruction of important ecosystems, unsanitary waste disposal and improper land use (NEPS and NACIAD, 1984).
At the same time, the area's geoenvironmental condition is changing. The vicinity of itogon Province is considered to be an area where mass movement or the possibility of it occurring, is high (DNER and NEDA, 1994). The 1990 Luzon earthquake caused numerous slope failures in Banguet and itogon provinces. This, coupled with strong typhoons, hastened the sediment erosion and deposition process. The sediments find their way to the Pangasinan lowlands and eventually into the Lingayen Gulf, both major sources of livelihood in northwestern Luzon. The earthquake also induced liquefaction particularly in Dagupan area. The 1991 Mt. Pinatubo eruption contributed sediments that will also find their way into the gulf. Elsewhere, in La Union, the beachline configuration of the Santo Tomas Spit is changing due to rapid coastal erosion. In particular, there is regression of about 200 meters along the coastline and growth of the spit landform by more than one kilometer southward.
This study is a part of the three-years Philippines-Japan cooperative undertaking by the Philippine Mines and Geoscience Bureau (MGB) under the Dept. of Environment and Natural Resources (DENR), the Nikko Exploration and Devt. Co., Ltd. (NED) and the Earth Remote Sensing Data Analysis Center (ERSDAC) of Japan.
This study is a part of the three-year Philippines-Japan cooperative undertaking by the Philippine Mines and Geosciences Bureau (MGB) under the Dept. of Environment and Natural Resources (DNIR), the Nikko Exploration and Devt. Co., Ltd. (NED) and the Earth Remote Sensing Data Analysis Center (ERSDAC) of Japan.
