Manual on Vulnerability Assessment of Watersheds
The Philippines is an archipelago whose islands are located on the western margin of the Pacific Ocean “Ring of Fire” and is undergoing mountain building through volcanic activities. The mountainous terrain includes mountain ranges and active volcanoes. Its geographic location being just north of the equator gives the country a moderate tropical climate suitable for crop production. However, the country is continuously threatened by natural and man-made hazards that resulted in loss of human lives and properties.
Basically, people live in a naturally formed hydrological unit called watershed. Of the total Philippine land area, about 70% is considered a major watershed which is found within 419 river basins all over the Philippine archipelago. However, its watersheds are naturally prone to environmental disasters due to several active faults, steep topography, poor vegetation cover and socio-economic pressures that contributed to the environmental disasters. Recent events such as the landslides in Ginsaugon, Leyte and Real, Quezon have highlighted the importance of identifying the vulnerability levels of our watersheds. If only development plans have identified vulnerability areas and included measures to reduce hazards, human sufferings and economic losses would have been avoided or reduced.
In support to Agenda No. 2 of the 12-point agenda of then DENR Secretary Angelo T. Reyes, the Research Sector banner project on the vulnerability assessment of selected characterized watersheds in the country was conceptualized and formulated. Vulnerability assessment is an approach in identifying and determining the degree to which a system is susceptible to or unable to cope with adverse effects of natural hazards such as soil erosion, flooding, landslides, pollution, forest/grass fires, etc. or man-made (anthropogenic) hazards. It has been designed as a rapid planning and decision making tool for application to address issues on the vulnerability of watersheds in order to minimize the risk to environmental disasters. Therefore, it is hoped that familiarizing the planners with an approach for incorporating hazard management into development planning can improve the planning process in the Philippines thereby giving hope for sustainable development.
Natural events such as earthquakes, typhoons, and heavy rains can be hazardous and pose a major threat to human beings. Moreover, the effect may be aggravated by actions made by man that would likely increase the vulnerability or lack of action to anticipate and mitigate the potential damages of these events.
Watershed is one of the basic life-supporting ecosystems that is threatened by the abovementioned environmental disasters (natural and man-made) because of its biogeophysical attributes and its socio-economic significance. Thus, in order to minimize its further destruction and degradation, assessing the vulnerability of a watershed to soil erosion, landslides, flooding, forest/grass fire and biodiversity loss is of utmost importance. The assessment can provide information in coming up with an integrated watershed management plan.
   Download VA Manual.pdf (3.13 Mb)