SAR-based flood monitoring for flatland with frequently fluctuating water surfaces: Proposal for the normalized backscatter amplitude difference index (NoBADI)

Hiroto Nagai*, Takahiro Abe, Masato Ohki

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Space-based synthetic aperture radar (SAR) is a powerful tool for monitoring flood conditions over large areas without the influence of clouds and daylight. Permanent water surfaces can be excluded by comparing SAR images with pre-flood images, but fluctuating water surfaces, such as those found in flat wetlands, introduce uncertainty into flood mapping results. In order to reduce this uncertainty, a simple method called Normalized Backscatter Amplitude Difference Index (NoBADI) is proposed in this study. The NoBADI is calculated from a post-flood SAR image of backscatter amplitude and multiple images on non-flooding conditions. Preliminary analysis conducted in the US state of Florida, which was affected by Hurricane Irma in September 2017, shows that surfaces frequently covered by water (more than 20% of available data) have been successfully excluded by means of C-/L-band SAR (HH, HV, VV, and VH polarizations). Although a simple comparison of pre-flood and post-flood images is greatly affected by the spatial distribution of the water surface in the pre-flood image, the NoBADI method reduces the uncertainty of the reference water surface. This advantage will contribute in making quicker decisions during crisis management.

Original languageEnglish
Article number4136
JournalRemote Sensing
Volume13
Issue number20
DOIs
Publication statusPublished - 2021 Oct 1

Keywords

  • ALOS-2
  • Flood
  • Florida
  • Hurricane Irma
  • NoBADI
  • PALSAR-2
  • SAR
  • Sentinel-1

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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