Flood delineation and damage assessment, France (2016-06-03)

<br>
Activation date: 2016-06-03 <br>
Event type: Flood <br>
<br>
Activation reason: <br>
In late May and early June 2016 flooding began after several days of heavy rain. The Loing and Seine rivers burst their banks and 4,000 people were evacuated from the town of Nemours. Some areas reported the worst flooding seen in a century.This activation was requested by the Ministère de l’Intérieur, Direction Générale de la Sécurité Civile et de la Gestion des Crises (COGIC).The scope of the request is to map flooding extents, infer maximum flooding and flood water depths, and assess the damage caused by the floods.  Products include the following:Observed flood extent mapping – carried out principally by SAR Image classificationVarious SAR and optical sensors were used, including Sentienl-1, Radarsat-2, Cosmo-SkyMed, Deimos-2, Landsat-8 and Pléades.Maximum flood extent and estimated water depth mappingThe flood extent was computed by extrapolating the observed flood extent by the using a reference Digital Surface Model  (DSM) , the IGN BD Alti® (5m).The water depth is derived from the height difference between water surface of the maximum flood extent and the minimum values of the riverbed indicated by the DSM.Impact assessment on land useCreated from the overlay of the maximum flood extent contour and water depth layer over the land use/cover data.Impact assessment on populationCross-tabulation of the maximum flood extent and water depth layers with the population density data as a function of continuous and discontinuous urban fabric.  <br>
<br>

启用日期：2016-06-03
事件类型：洪涝灾害

启用缘由：
2016年5月末至6月初，连续多日强降雨引发洪涝灾害。卢万河（Loing）与塞纳河（Seine）河堤溃决，内穆尔（Nemours）镇共有4000名民众被疏散。部分区域遭遇了百年一遇的严重洪涝。本次数据启用申请由法国内政部、民防与危机管理总局（Ministère de l’Intérieur, Direction Générale de la Sécurité Civile et de la Gestion des Crises，简称COGIC）提出。本次申请的工作范畴为绘制洪涝淹没范围、推演最大淹没范围与洪水水深，并评估洪涝引发的损失。

本次生成的产品如下：
1. 实测洪涝范围制图：主要通过合成孔径雷达（Synthetic Aperture Radar，SAR）图像分类技术完成。本次研究使用了多种合成孔径雷达与光学传感器，包括哨兵-1（Sentinel-1）、雷达卫星-2（Radarsat-2）、Cosmo-SkyMed、Deimos-2、陆地卫星8号（Landsat-8）以及Pléiades。
2. 最大淹没范围与估算洪水水深制图：通过参考数字表面模型（Digital Surface Model，DSM）——法国国家地理研究所BD Alti®（5米分辨率），对实测洪涝范围进行外推计算，得到最大淹没范围。洪水水深则通过最大淹没范围的水面高度与数字表面模型标注的河床最低高度之差推导得出。
3. 土地利用影响评估：将最大淹没范围图层与水深图层叠加至土地利用/覆盖数据之上，完成洪涝对土地利用的影响评估。
4. 人口影响评估：将最大淹没范围与水深图层，与按连续与非连续城市用地类型划分的人口密度数据进行交叉制表分析。