Satellite-based flood inundation and damage assessment

Abstract

Abstract Because recurring floods in the Philippines have become more damaging throughout time, risk assessments, quantifying, and visualizing flood damages as accurately as possible become imperative. To deal with an up-to-date database and a practical assessment tool, a satellite imagery-based method was used which aimed to map flood inundation and estimate damages brought by the flood during Typhoon Ulysses. This paper presents a framework for an integrated flood risk management in a river basin context with the following components as follows: 1) collection of the comprehensive database containing information relevant for flood analysis; 2) use of a satellite-imagery based method for flood inundation map using Google Earth engine; 3) validation of map accuracy through quick post-flood participatory approach. Analysis of the recent flood inundation event in November 2020 in Cagayan Valley, Philippines showed the inundation of an extensive area of 620.88 km 2 affecting the Cagayan province at 55.91% and Isabela province at 44% share of inundation. The flood severely affected approximately 614.05 km 2 of the total croplands. Using a participatory validation approach, the overall accuracy of datasets used is 97.78% while flood extent is 95%. Through this study, the framework, approach, and methodology can be replicated in other locations in the Philippines and in other countries which recurrently experience flooding.