Volume 25 Nos. 1&2
Vulnerability assessment of the La Mesa Watershed Reservation, Quezon City, Philippines
The vulnerability assessment of the La Mesa Watershed Reservation in Novaliches, Quezon City was conducted to provide the basis for the formulation of a sustainable watershed development and management plan. The guidelines on vulnerability assessment prepared by Daño (2006) of the Ecosystems Research and Development Bureau (ERDB) was also tested in the identification of vulnerable areas in the La Mesa Watershed. Four priority environmental hazards were assessed in the study area using a spatial analysis tool, the ArcGIS Model Builder. The composite map identified a total of 10.285 ha of very highly vulnerable areas distributed as follows: soil erosion (0.285 ha), landslide (0.014 ha), biodiversity loss (8.685 ha), and fire (1.141 ha).
San Cristobal Watershed vulnerability assessment to soil erosion and water pollution
The study reviewed the characterization report of San Cristobal Watershed located in Laguna, Cavite, and Batangas. Its vulnerability to soil erosion and water pollution was assessed and mitigation and adaptive measures were recommended to address erosion and pollution hazards. Hazards and their contributory factors were determined through analysis of biophysical and socio-economic data and conduct of focus group discussion (FGD). Locations where hazards have been observed were recorded and inputted in the maps generated using geographic information system (GIS) software.
The watershed provides various functions aside from contributing an estimated 5% of the total freshwater discharge to Laguna Lake. The study revealed that out of the total area of the watershed (14,162 ha), 1,173 ha located mainly in the upstream portion was zoned as highly vulnerable to soil erosion. Vulnerability of the water resource was attributed to the water quality problem brought about by the fastpaced conversion of agricultural lands into subdivisions and factory areas. Three vulnerability levels (very high, high and moderate) were developed for specific stretches of the river system. The upstream portion of the river was classified as moderate due to lesser level of development in the area compared to the other portions of the watershed. In the formulation of a Watershed Management Plan, interventions should focus on minimizing soil erosion and improving the water quality of the river.
Landslide vulnerability assessment of Kisloyan subwatershed in Mindoro Island, Philippines
Kisloyan subwatershed is one of the crucial sources of water to the Magasawang Tubig River. Mag-asawang Tubig River is one of the major rivers in Oriental Mindoro that provides irrigation and domestic water to at least three of the big towns in the province and serves as a natural habitat to endemic and endangered flora and fauna. However, it is threatened because of nickel and cobalt extraction, with deposits considered as one of the largest in the Far East. A total mining area of 1,435.90 ha is administratively shared by the municipalities of Victoria, Oriental Mindoro and Sablayan, Occidental Mindoro.
This study determined the landslide vulnerability of the Kisloyan subwatershed to come up with recommendations on how to mitigate the impacts of this hazard. Vulnerability assessment was conducted based on the natural characteristics and the man-induced attributes of the site.
Results of the study indicated that the Sablayan, Occidental Mindoro portion has the highest vulnerability to landslide, particularly to geological risks.
Application of analytic hierarchy process and GIS in landslide vulnerability assessment of Matutinao Watershed, Cebu, Philippines: A case study anchored on the climate change framework
The study was conducted in the ecologically and economically significant Matutinao Watershed in Cebu. Ongoing developmental activities in the area necessitate a landslide vulnerability assessment to avoid possible losses of lives and properties. A GIS-assisted approach was developed to a) evaluate the utility of GIS with regard to landslide vulnerability assessment anchored on the climate change framework; b) identify and map out the areas vulnerable to landslide; recommend appropriate measures to avoid loss of lives and properties; and c) formulate policy recommendations. Using the Analytical Hierarchy Process (AHP) in determining the relative importance of factors identified and GIS, the landslide vulnerability anchored in a climate change perspective was determined. Exposure to landslide was based on 2020 climate projections. The sensitivity was computed based on the model derived from AHP, expressed as L = 0.8297[0.3160Sl + 0.0973R + 0.0973T + 0.0912Ga + 0.0912Gf + 0.1729Gfl+ 0.0698So + 0.0633Lu] + 0.1703[0.2532FS + 0.3175H + 0.4349GD].