Large-scale Flood Monitoring: Where is the most exposed to large flood in Asia?

Abstract:

Flood mapping and monitoring (particularly flood areas, locations, and durations) are an imperative process and are the fundamental part of risk management as well as emergency response. We have found that Bangladesh is the highest risk country among 14 Asian developing countries from flood risk assessment under climate change scenarios because of its largest vulnerable population to cyclic 50-year flood events.

This study shows a methodological possibility to be used as a standard approach for continental-scale flood hazard and risk assessment with the use of multi-temporal Moderate Resolution Imaging Spectrometer (MODIS), a big contributor to progress in real-time hazard mapping. The purpose of this study is to detect flood inundation areas considering the flood propagation even with limitations of optical and multispectral images. We improved a water detection algorithm to achieve a better discrimination capacity to discern flood areas by using amodified land surface water index (MLSWI), and estimated flood extent areas, coupled with the water level and an optimal threshold ofMLSWI based on the spectral characteristics.

In Bangladesh, the FFWC warns people that floods occur when the water level exceeds the danger level. We clearly confirmed that the flood propagation was in good agreement with the timing of the water level exceeding the water danger level in the case of the cyclic 10-year flood event. The flooding was also found to be proportional to theflood extent (areas) and duration. The results showed the novel approach’s capability of providing instant,comprehensive nationwide flood mapping over the entire Bangladesh by using multi-temporal MODIS data. The ambiguities of rapid flood mapping from satellite-derived products were verified in the Brahmaputra River by using high-resolution images (ALOS AVNIR2, spatial resolution 10m), ground truth and field survey data.