Flood Depth Estimation Using Synthetic Aperture Radar (SAR) Imagery and Topography: A Case Study of the 2021 and 2022 Floods in Hawkesbury Valley, Australia

Floods are among the most common and devastating extreme weather events that cause damage to infrastructure, agricultural lands, transportation and communication systems. To effectively respond to floods, it is important to have accurate information about the depth of floodwater across the affected area, and ground surveys are not always possible in such scenarios. This information can be estimated remotely through the use of spaceborne synthetic aperture radar (SAR) systems, which are equipped to operate under nearly all weather and time conditions. Here, we present a case study of estimating the flood depth using inferred flood extents from the very high resolution (VHR) Capella Space X-band constellation. We have used a publicly available digital elevation model (DEM) with a Python-based implementation of the Floodwater Depth Estimation Tool (FwDET) to determine flood depth from the SAR imagery. We estimated the depth of floods in two major flood events (March 2021 and March 2022) in Hawkesbury Valley, New South Wales, Australia. Furthermore, we explored the utility of these depth maps for rapid flood damage assessments.