DAM-Net: Global Flood Detection from SAR Imagery Using Differential
  Attention Metric-Based Vision Transformers
Tamer Saleh Xingxing Weng Shimaa Holail Chen Hao Gui-Song Xia
The detection of flooded areas using high-resolution synthetic aperture radar
(SAR) imagery is a critical task with applications in crisis and disaster
management, as well as environmental resource planning. However, the complex
nature of SAR images presents a challenge that often leads to an overestimation
of the flood extent. To address this issue, we propose a novel differential
attention metric-based network (DAM-Net) in this study. The DAM-Net comprises
two key components: a weight-sharing Siamese backbone to obtain multi-scale
change features of multi-temporal images and tokens containing high-level
semantic information of water-body changes, and a temporal differential fusion
(TDF) module that integrates semantic tokens and change features to generate
flood maps with reduced speckle noise. Specifically, the backbone is split into
multiple stages. In each stage, we design three modules, namely, temporal-wise
feature extraction (TWFE), cross-temporal change attention (CTCA), and
temporal-aware change enhancement (TACE), to effectively extract the change
features. In TACE of the last stage, we introduce a class token to record
high-level semantic information of water-body changes via the attention
mechanism. Another challenge faced by data-driven deep learning algorithms is
the limited availability of flood detection datasets. To overcome this, we have
created the S1GFloods open-source dataset, a global-scale high-resolution
Sentinel-1 SAR image pairs dataset covering 46 global flood events between 2015
and 2022. The experiments on the S1GFloods dataset using the proposed DAM-Net
showed top results compared to state-of-the-art methods in terms of overall
accuracy, F1-score, and IoU, which reached 97.8%, 96.5%, and 93.2%,
respectively. Our dataset and code will be available online at
https://github.com/Tamer-Saleh/S1GFlood-Detection.