Abstract
The threshold-based Landslide Early Warning System (LEWS) is an innovation to the existing MGB scheme of providing landslide warning to the Local Government Units (LGUs) in Albay. It aims to provide accurate, easy-to-interpret, timely, and regularly updated landslide warning information. The author, with the help of MGB-V, designed the LEWS and had it tested during Typhoon Ulysses in November 2020. The results were then used in the calibration of rainfall thresholds for better performance.
The LEWS is based on rainfall thresholds derived from the analysis of rainfall and landslide initiation. The calculation of thresholds focused on two (2) rainfall parameters, the rainfall intensity, and the event rainfall. It also considered the geologic and geomorphic conditions in Albay and divided the province into different warning landscapes. After determining the rainfall thresholds, subsequent calibration was made using a new rainfall-landslide dataset.
One of the key objectives of the LEWS is to empower LCEs and LDRRMOs in making critical decisions concerning landslide preparedness and safety measures. It also seeks to contribute to the long-term goal of reducing casualties due to landslides. To ensure its success and sustainability, continued engagements to strengthen partnerships and promote collaborations with LGUs and other key stakeholders should be pursued. With concerted efforts and with resources focused on attaining one shared goal, the project could be truly instrumental in reducing landslide casualties.
Introduction
In the Philippines, the Province of Albay is considered one of the areas that have long been affected by landslides. Some of the past landslide disasters have brought considerable damage and claimed hundreds of lives in Albay. The most recent of these happened during Tropical Depression (TD) “Usman” on December 28-29, 2018, where at least 15 people were killed and another 10 were injured.
For the past seven (8) years, MGB-V flood and landslide threat advisories have been regularly issued to both Barangay and Municipal/City LGUs during the conduct of field mapping, and in times of
impending tropical cyclones. The issuance of both flood and landslide threat advisories normally ensues after the Pre-Disaster Risk Assessment (PDRA) meeting called for by the Regional Disaster Risk Reduction and Management Council (RDRRMC), through the Office of Civil Defense V (OCD-V). It is quite unfortunate and alarming, that even with the issuance of these threat advisories, landslide casualties continue to happen.
Feedback and comments from some Local Disaster Risk Reduction and Management Officers (LDRRMOs) in Bicol, as expressed during meetings and forums, showed the inherent difficulty in using warning information contained in the MGB-V landslide threat advisories, since it doesn’t tell when landslides may initiate. LGUs have also complained about the unavailability and inaccessibility of real- time rainfall data, which can be used in combination with the arguably ambiguous landslide warning information, as the basis of their respective evacuation protocols and contingency plans. On the other hand, it may also be possible that some of these LGUs might have failed to utilize the warning information provided to them promptly and properly. In this case, it is apparent that the problem now lies in the operational use of warning information. These, together with several socio-political factors, could be the very reasons why several casualties continue to be recorded because of landslides.