Results of coastal geohazard assessment in Calumpan Peninsula, Mabini, Batangas conducted by a team from the Marine Geological Survey Division indicated that the area is at high risk to coastal geohazards. Out of the 18 barangays assessed, 14 were rated as highly susceptible to coastal erosion. Much of the shorelines surveyed appear especially vulnerable to landslide.

Calumpan, a popular marina area is also famous for interesting dive sites. This prominent topographic high juts out in southern Batangas bounded to the southwest by Maricaban Strait, by Balayan Bay to the northeast and the Batangas Bay to the southeast. It is generally underlain by volcanic rocks and breccias with patches of limestone and at places with recent unconsolidated sediments.The peninsula is generally long, ridged with steep coastlines. Hence, it is highly exposed to impacts of strong waves during Habagat and even during Amihan seasons. Off the beach, the terrane is gently to steeply sloping with walls lined with corals, sponges and variety of fishes. Lubang Fault is also proximate which could trigger earthquakes or other geologic upheavals.Aside from natural factors, seawalls constructed around the peninsula aggravate the risk to coastal erosion. These defences reflect and concentrate wave energy causing sediments starvation downdrift which can exacerbate further erosional problems.

Aside from the risks of coastal erosion, houses were built fronting cliffs especially those on the western portion of the peninsula which can be weakened by earthquakes or excessive rainfall leading to coastal landslides. Anyway, some fringing reefs were observed at places which could serve as buffer or dissipateragainst attacks of strong waves.

The coast is generally retreating prone to flooding which is critical for houses and infrastructures built along or near the present high tide level.

By: Marine Geological Survey Division


Figure 1. Seawalls and small makeshift quays built along Barangay Bagalangit and other adjacent barangays are supposedly protecting the community but on the contrary, are aggravating coastal erosion preventing transport/deposition of sand along the beach


Figure 2. Port of a commercial infrastructure in Barangay Calamias impedes regular flow of sediments causing erosion in the downdrift.  Plastic wastes are commonly seen admixed with beach sediments which are also dangerous to humans and sea organisms


Figure 3. Dive resorts in Barangay San Jose, Mabini found constructed along the beach slope in front of the mandatory “ coastal easement zone” is generally exposed to retreating beach brought about by coastal erosion and effects of rising sea level