A Multi-Hazard Interactions Framework for the Philippines

A multi-hazard interaction includes one natural hazard triggering or increasing the probability of another hazard occurring, or two hazards coinciding with one another such that they impact the same region and time. The Philippines, due to its unique geologic, geographic, and climatological setting experiences a wide variety of natural hazards making it both an ideal study area for multi-hazard interactions as well as a high-risk area for the impacts of these hazards. Examples of multi-hazard interaction events in the Philippines include the (i) 1991 Mt. Pinatubo eruption which caused severe lahars and global cooling, (ii) numerous tropical cyclones that cause floods, storm surges, and landslides, and (iii) eruptions of Taal Volcano that have triggered lacustrine tsunamis through various eruptive products and processes. Here we begin the steps of constructing a regional multi-hazard interactions framework for the Philippines using a matrix built from the records of past occurrences. A wide array of past events from peer-reviewed and grey literature are reviewed to generate a regional matrix composed of 38 hazard subtypes of 19 hazard types grouped into 6 major categories. Most of the records have contributed to a growing database of geophysical, hydrological, and atmospheric hazard interactions while there are much fewer records of or studies on shallow earth, biophysical, and space-based hazard interactions. The matrix is constantly being updated as new and obscure data sources become available, with the current matrix and its existing entries providing an overview of the diverse hazard interactions in a constrained geographic location and serving as a historically-grounded reference for responding to disaster risk posed by these hazard interactions.