Subsidence Susceptibility Mapping in Tropical Island Karst: A comparison of approaches used in the Municipality of General Luna in Siargao Island, Philippines

Authors

  • Hugo, Marie Krystel D.
  • Agot, Ross Dominic D.
  • Manzano, Liza Socorro J.
  • Esmeralda, Aquila Kristian B.
  • Abracia, Aaron Miguel C
  • Madrigal, Madonna Feliz B.
  • Ondona, April C.
  • Dela Torre, Angelo Ma. Gabriel P.
  • Isip, Marcius Elaeo G.
  • Rivera, John Michael D.
  • Umali, Julius Vincent P
  • Belesario, Nelgie Ann C

Keywords:

Geohazards, Karst, Subsidence, Susceptibility Mapping, Sustainable Tourism

Abstract

Karst subsidence hazard susceptibility mapping is an integral part of the National Geohazards Assessment and Mapping Program (NGAMP) initiated by the Mines and Geosciences Bureau (MGB) in 2013. It aims to comprehensively assess geohazards in karst regions in the Philippines. The mapping process involves three primary procedures: remote sensing interpretation of IfSAR[1]derived Sink Depth Maps using ArcGIS, geological and geomorphological assessment, and geophysical survey using Ground Penetrating Radar (GPR). This method considers sinkhole distribution, other karst features, ground movement evidence, and GPR survey results to identify subsidence-prone areas. The approach generates Karst Subsidence Susceptibility Maps indicating highly vulnerable regions, considering the unpredictable nature of sinkhole collapse.

To enhance the methodology and susceptibility classifications, the PhilKARST Program of MGB introduced the statistical Weights of Evidence (WoE) analysis and employed in General Luna, a prominent tourist destination in Siargao Island, Philippines. This approach ensures consistency and reproducibility by examining the correlation between hazard inventories and fifteen (15) conditional factors.

The resultant weights are determined to generate a subsidence susceptibility index map with Low, Moderate, High, and Very High ratings. Evaluation of true- and false-positive rates using available training data indicated an initial success rate of 82.2% for subsidence susceptibility modeling, signifying reliable results. The enhanced susceptibility map for General Luna in Surigao del Norte, displays lower susceptibility classifications in areas with fewer or no sinkhole occurrences. This differs from the output map of the previous method, which exclusively highlighted highly susceptible areas based on sinkhole distribution, other karstic features, and GPR surveys.

References

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Published

2024-02-14

How to Cite

Marie Krystel D., H. ., Ross Dominic D. , A., Liza Socorro J. , M., Aquila Kristian B., E., Aaron Miguel C, A., Madonna Feliz B, M., April C. , O., Angelo Ma. Gabriel P, D. T., Marcius Elaeo G., I., John Michael D, R., Julius Vincent P, U., & Nelgie Ann C, B. (2024). Subsidence Susceptibility Mapping in Tropical Island Karst: A comparison of approaches used in the Municipality of General Luna in Siargao Island, Philippines. Thai Geoscience Journal, 4(5), 1–10. Retrieved from https://ph03.tci-thaijo.org/index.php/TGJ/article/view/1801

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