Mapping the karstification potential of central Cebu, Philippines using GIS

Karstification is influenced by numerous factors, such as climate, geomorphology, and geology. Karstified areas are faced with numerous problems such as ground subsidence and groundwater vulnerability. In rapidly urbanizing areas like Cebu in the Philippines, it is imperative to know the karstification potential, especially if karst landforms are already present. We evaluated the karstification potential of central Cebu using Raster Overlay Analysis (ROA) in a geographic information system (GIS) platform. ROA uses multiple maps which represent different factors affecting karstification, such as precipitation, temperature, vegetation, elevation, slope, drainage, lineaments, and geology. These factors were then correlated with the karstification potential map using the Cell Statistics tool. ROA reveals that 17% of central Cebu has very low karstification potential, while < 65% has low to moderate karstification potential and 18% has high to very high karstification potential. High karstification potential is generally associated with high precipitation (> 2100 mm/yr), low temperature (< 24.5 °C), very dense vegetation, high elevation (> 787 masl), gentle slope (< 10°), very high lineament density (> 0.45), very low drainage density (0), and older limestone bedrock. Areas with moderate to very high karstification potential coincide with cave locations. Cell Statistics (Range) reveals that the karstification potential map is strongly correlated with precipitation and temperature, and weakly correlated with drainage density and geology. While assumed to greatly affect karstification, the weak correlation of local geology with the karstification potential is attributed to lithological heterogeneities in central Cebu. Information on an area’s karstification is beneficial to effective land use planning and reduction of karst-related hazards.