A Tool for Pre-Operational Daily Mapping of Floods and Permanent Water Using Sentinel-1 Data

Abstract

An automated tool for pre-operational mapping of floods and inland waters using Sentinel-1 data is presented. The acronym AUTOWADE (AUTOmatic Water Areas DEtector) is used to denote it. The tool provides the end user (Italian Department of Civil Protection) with a continuous, near real-time (NRT) monitoring of the extent of inland water surfaces (floodwater and permanent water). It implements the following operations: downloading of Sentinel-1 products; preprocessing of the products and storage of the resulting geocoded and calibrated data; generation of the intermediate products, such as the exclusion mask; application of a floodwater/permanent water mapping algorithm; generation of the output layer, i.e., a map of floodwater/permanent water; delivery of the output layer to the end user. The open floodwater/permanent water mapping algorithm implemented in AUTOWADE is based on a new approach, denoted as buffer-from-edge (BFE), which combines different techniques, such as clustering, edge filtering, automatic thresholding and region growing. AUTOWADE copes also with the typical presence of gaps in the flood maps caused by undetected flooded vegetation. An attempt to partially fill these gaps by analyzing vegetated areas adjacent to open water is performed by another algorithm implemented in the tool, based on the fuzzy logic. The BFE approach has been validated offline using maps produced by the Copernicus Emergency Management Service. Validation has given good results with a F1-score larger than 0.87 and a kappa coefficient larger than 0.80. The algorithm to detect flooded vegetation has been visually compared with optical data and aerial photos; its capability to fill some of the gaps present in flood maps has been confirmed.

Hydrometeorological Extreme Events in Africa: The Role of Satellite Observations for Monitoring Pluvial and Fluvial Flood Risk

“…2. The flood extent was derived from the Sentinel-1 image using the method proposed by Chini et al (2019) and from the Sentinel-2 image using the one proposed by Pulvirenti et al (2021). As can be seen in Fig.…”

Integrated Flood Impact and Vulnerability Assessment Using a Multi-Sensor Earth Observation Mission with the Perspective of an Operational Service in Lombardy, Italy

“…Optical and microwave technologies are used for flood monitoring; however, the synthetic aperture radar (SAR) offers more accurate real-time data on flood extent and water depth due to its cloud and vegetation penetration capabilities [44,45]. For instance, band C (e.g., Sentinel 1, hereafter S1) and band X (e.g., TerraSar-X, hereafter TSX; COSMO) are among the most used bands for flood detection [46,47]. The availability of multitemporal satellite data allows for continuous flood monitoring through pre-operational and operational services [47,48], where SAR has tripled compared to optical sensors [49].…”

“…For instance, band C (e.g., Sentinel 1, hereafter S1) and band X (e.g., TerraSar-X, hereafter TSX; COSMO) are among the most used bands for flood detection [46,47]. The availability of multitemporal satellite data allows for continuous flood monitoring through pre-operational and operational services [47,48], where SAR has tripled compared to optical sensors [49]. Between 2016 and 2020, SAR imagery was used 76% of the time for flood detection, compared to only 24% for optical sensors, demonstrating its potential [50].…”

“…Integrating these advantages with the new IRIDE like SAR technologies can produce clear and actionable results for disaster response. Multi-sensor approaches usually consider one or two satellites [47,51,52]. Thus, satellite Earth Observation, owing to the wide range of remotely sensed information available, plays a major role in the provision of spatial products and offers the opportunity to map highly vulnerable flood-prone areas.…”

Sparse Representation-Based Inundation Depth Estimation Using SAR Data and Digital Elevation Model

“…There is a vast literature on methodologies used to identify floodwaters. Most studies lie on the physical mechanism of radar backscattering in different land uses, such as flat soil, water bodies, and urban areas [8], [9], [10], [11]. A study on the effect of the satellite observation modes and orbit conditions in flood mapping was performed in [12].…”