Retrospective flood analysis in Luxembourg, July 2021 (2022-10-11)

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Activation date: 2022-10-11 <br>
Event type: Other <br>
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Activation reason: <br>
The CEMS Risk and Recovery Standard has been activated for a retrospective assessment of an extreme flooding across Western Europe in summer 2021, which had devastating impacts on Luxembourg. Institute MeteoLux, the Luxembourgish meteorological institute, reported torrential rains broke two records for the month of July at the weather station at Luxembourg-Findel Airport. The maximum precipitation in 12 hours and 24 hours reached accumulations of 74.2 mm and 79.4 mm, beating the previous records set on 22 July 2016 of 60.4 mm / 70.6 mm. Flooding was recorded on almost all water bodies in Luxembourg. Particularly affected were the localities along the rivers Alzette and the lower Sauer. According to the Luxemburgish Water Management Agency, the one hundred year high water mark was exceeded at nine gauging stations all over the country.The evidence of flood within Sentinel-1 images led to focus the analysis on two AOIs: AOI01-Mersch and AOI02-Bettembourg.A hydraulic modelling approach has been adopted to provide the temporal analysis of the occurred flood event (P06 product) in terms of maximum flood extent, maximum water depth, and flood temporal evolution estimated during the period 15 July 2021 – 17 July 2021. The model has been calibrated using two P04-Flood delineation products depicting the flood footprint extracted from Sentinel-1 acquisitions taken on the 15 July (579.6 ha in AOI01 and 576.2 ha in AOI02) and 16 July 2021 (317.4 ha in AOI01 and 229.2 ha in AOI02).The maximum flood extent retrieved from the hydraulic modelling is 4,729.5 ha in AOI01 and 2,100.5 ha in  AOI02. The water depth range has been estimated between 0.25 m and 2.5 m on both AOIs.The impact assessment analyses on assets and population has been performed based on the available reference data (i.e., transportation and building footprints) as derived from OpenStreetMap (OSM), the GlobeLand30 dataset, and the population information provided by the WorldPop dataset. The product has been delivered by reporting, in tabular form, the impacts of the maximum flood extent provided by the P06 product. <br>
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