GEOLOGICAL SOCIETY OF THE PHILIPPINES

LOCATION OF POSSIBLE GROWTH SITES FOR BUTUAN CITY WITH MINIMAL GEOHAZARDS

 

Dulcisimo S. Domingo, Claro Jose C. Manipon, and Raymund Abundo

GDIS Section, Lands Geological Survey Division, Mines and Geosciences Bureau

 

Butuan City perennially suffers from severe flooding brought about by its precarious location along the banks of Agusan River. The other natural threat to this city has been identified as the following: (1) liquefaction; (2) sea level rise; and (3) high peak ground acceleration due to its proximity to the Philippine fault. Previous workers have even considered the possibility of the effect of tsunami in the proximity of the area.

Digital terrain modeling of the Agusan delta reveals wide areas of possible inundation. It has even revealed wide depressions in the Northeast previously undetected y casual observation of the topographic map. Deterministic ground acceleration modeling using the equation proposed by Fukushima and Tanaka (1990) using the Philippine Fault as earthquake generator at magnitude 7 shows wide areas of high g values.

Terrain mapping in the study area showed remnants of bedrock now manifested as isolated low hills. Wide alluvial fans were also identified all along the mountain slopes. These terrain units and Geo hazard areas were then subjected to Boolean operators to locate possible sites where the city could further develop and retain its metropolitan character. These sites were identified at some distance west and southwest of the city. These were sizeable enough, onto which a new butuan City could rise.

 
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