Vol. 25 Nos. 1&2


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Vulnerability assessment of the La Mesa Watershed Reservation, Quezon City, Philippines

Esmeralda P. Andres

Supervising Science Research Specialist

Ecosystems Research and Development Service

DENR-National Capital Region

North Avenue, Quezon City, Philippines

Email address: esmie.andres@gmail.com

Manuel S. Sabater

Community Enviroment and Natural

Resources Officer

Email address: mss_iise@yahoo.com

Rudolfo Espada, Jr.

Planning Officer I

Email address: rudolf_espada@yahoo.com

Eduardo C. Calzeta

Forester II

Email address: ed_calzeta@yahoo.com

Riza C. Arjona

Science Aide

Email address: rizmagcar@yahoo.com

 

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).

Keywords: Vulnerability assessment, La Mesa Watershed Reservation, ecological profiling and characterization,

soil erosion vulnerability, landslide vulnerability, fire vulnerability, biodiversity loss vulnerability, Metro Manila, Philippines


San Cristobal Watershed vulnerability assessment to soil erosion and water pollution

Antonio M. Daño, Ph. D.
Supervising Science Research Specialist
Ecosystems Research and Development Bureau (ERDB),
College, Laguna, 4031
Email address: tonydano093 
Karen Rae M. Fortus
Science Research Specialist I

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.

 Keywords: Vulnerability assessment, watershed characterization, Geographic Information Systems, hazards, soil erosion


Landslide vulnerability assessment of Kisloyan subwatershed in Mindoro Island, Philippines

Edgardo E. Vendiola, PhD
OIC-Regional Technical Director for Research (retired)
Ecosystems Research and Development Service
Department of Environment and Natural Resources
Region IV-B, Roxas Blvd., Manila
Forester Marilyn R. Limpiada
Science Research Specialist II
Email address: erds4b@gmail.com 

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.

 Keywords: Kisloyan subwatershed, vulnerability assessment, watershed, geological hazards, landslide, geospatial technology

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

Reynaldo L. Lanuza
Supervising Science Research Specialist
Ecosystems Research and Development Bureau
ERDB-BCWERC
Banilad, Mandaue City
Email address: reyllanuza@yahoo.com
Daisy Luisa S. Camello
Statistician II
Antonio M. Daño, PhD
Supervising Science Research Specialist
ERDB, College, Laguna
Bruno O. Carreon
Science Research Specialist I

 The study was conducted in the ecologically and economically significant Matutinao Watershed in Cebu. Ongoing developmental activities in the area necessitates 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].


Keywords: GIS-assisted approach, landslide, vulnerability assessment, Matutinao Watershed, Geographic Information System, Analytic Hierarchy Process