[H-DS08] Human environment and disaster risk

[HDS08-P02] Flood damage mapping of 2020 Typhoon Ulysses in the Philippines

*Naoko Nagumo¹, Kentaro Aida¹, Miho Ohara¹, Masakazu Fujikane¹ (1.International Centre for Water Hazard and Risk Management, PWRI)

Keywords: typhoon, satellite image, flood, damage, Philippines

Typhoon Ulysses (international name: Vamco) crossed the Central Luzon Region of the Philippines in November 2020, bringing strong winds and torrential rainfall and causing 101 casualties throughout the country. The numbers of flooding and landslide/soil collapse were 264, while affected municipalities/cities reached 541 and affected persons were 5,184,824 in total (as of 13 January 2021). Also, the maximum numbers of evacuees reached to 556,318 (as of 15 November 2020). In flood-prone countries such as the Philippines, hazards and damage should be carefully investigated, and the collected data should be systematically sorted out for future disaster response, recovery and flood risk assessment. However, it is often difficult to get a whole picture of a disaster, especially when it is a widespread event. In addition, the recent worldwide pandemic of COVID-19 has made it difficult for experts to conduct sufficient field surveys. Therefore, this study conducted flood-related data mapping using satellite observation rainfall, satellite images and reports released on the web by the National Disaster Risk Reduction Management Council (NDRRMC) of the Philippines to understand the floods and damage caused by Typhoon Ulysses. Rainfall due to Typhoon Ulysses was particularly intense in the eastern part of Luzon Island; the 3-day-rainfall reached over 300 mm between 11 and 14 November. As a result, several rivers flooded at different locations of the island. The flood events of the Pasig-Marikina River in Metro Manila and the Cagayan River in Cagayan Valley Region, Northern Luzon, have been considered the most serious since the 2009 flood by Typhoon Ondoy and the 1980 flood by Typhoon Aring, respectively. Large numbers of people were reported to be affected in the regions of Central Luzon, Cagayan Valley, Bicol and Metro Manila as they lived along the typhoon course, while the house damage was concentrated in the regions of Central Luzon and Bicol. Also, 2991 evacuation centers were opened three days after the typhoon landed and 324,617 persons were evacuated inside the evacuation centers along with the other 231,701 persons evacuated outside the centers across the country, and more than 30-40 % of the population was evacuated in some municipalities. Mapping both hazard and damage data can be instrumental in understanding the characteristics of a disaster spatiotemporally, and such analytic understanding will be useful not only for recording disasters but also for sharing a common view of a disaster and identifying the needs for further support.