Abstract
Remotely sensed flood extents obtained in near real-time can be used for emergency flood incident management and as observations for assimilation into flood forecasting models. High-resolution synthetic aperture radar (SAR) sensors have the potential to detect flood extents in urban areas through clouds during both day- and night-time. This paper considers a method for detecting flooding in urban areas by merging near real-time SAR flood extents with model-derived flood hazard maps. This allows a two-way symbiosis, whereby currently available SAR urban flood extent improves future model flood predictions, while flood hazard maps obtained after the SAR overpasses improve the SAR estimate of urban flood extents. The method estimates urban flooding using SAR backscatter only in rural areas adjacent to urban ones. It was compared to an existing method using SAR returns in both rural and urban areas. The method using SAR solely in rural areas gave an average flood detection accuracy of 94% and a false positive rate of 9% in the urban areas and was more accurate than the existing method.
Highlights
Flooding causes significant death, injury, displacement, homelessness and economic loss all over the world every year
This paper considers the merits of an alternative method of improving the accuracy of rapid post-event flood mapping in urban areas by merging precomputed flood return period (FRP) maps with VHR synthetic aperture radar (SAR)-derived flood inundation maps [43] and compares the method with that of [42]
There were no examples of defended regions in any of the test areas, and as a result, the effective height map for each area was very similar to its DSM, which explains the similarity of the results for Case 1 and Case 2
Summary
Injury, displacement, homelessness and economic loss all over the world every year. The risks to people and the economic impacts of flooding are greatest for urban flooding [1,2,3,4]. Regarding riverine floods in the UK, over 2 million properties (the majority of them in urban areas) are located in floodplains. The number of floods and the number of properties affected by them are likely to increase in the future, due to the growing population exposure in floodplains and the impact of climate change [6]. In economically strong and populated areas, global economic losses due to floods are projected to reach $597 billion over the period 2016–2035 [7]
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