Terrain classification and analysis was conducted through the following activities:

• Research – This activity involved the gathering of existing geological data from several concerned agencies, which include the geology. geomorphology, tectonic setting, seismicity, soils, well logs and other related information related to the study.
  

• Aerial Photo Interpretation – Aerial photographs with scales of approximately 1:25,000 (1979-1982 photography) and 1:18,000 (1994 aerial photography) covering parts of TLWA, were interpreted.
  

• Geomorphological, geological and other terrain characteristics were delineated. Existing road network, rivers and creeks were traced. The 1:50,000 NAMRIA topographic maps were used as base map and utilized to derive other terrain attributes, e.g. slope.
  

• Field Investigation – Fieldwork was conducted to verify the information gathered from the aerial photos and from the research work. Terrain mapping involving geological, geomorphological and geohazard mapping were conducted to identify underlying lithology, structures and potential geohazards per terrain mapping unit (TMU). Shallow auger drilling and test pitting were conducted on selected sites. Soil and water samples were also collected for various tests and determinations.
  

• Interviews – During the course of the field mapping activities, the team interviewed some residents within the TLWA to gather information on the possible recurrence / interval of geologic hazards e.g. flooding, landslide and seismicity.
  

Internal characteristics per TMU within the TLWA were gathered during the actual fieldwork. Additional information regarding geology and other aspects of the area’s environment were obtained from published and unpublished works from government agencies and private individuals.

Sources of secondary data were Phivolcs, PAGASA, BSWM, DIDP and PCEEM.