Detailed flood delineation in Hildesheim, Germany (2017-12-06)

<br/> Activation date: 2017-12-06 <br/> Event type: Flood <br/> <br/> Activation reason: <br/> The scope of the service request was to generate reference information, concerning flood events that occurred from July 25 to July 27 2017, within the Hildesheim district of the Lower Saxony State of Germany. General Reference content and Land Use/Cover products were produced along with flood specific products:The observed flood extentThe maximum flood extent&nbsp; &nbsp;Estimated Maximum Flood ExtentThe&nbsp;observed flood extent&nbsp;product was generated by appropriate processing of relevant SAR imagery during and after the flood event. A classification algorithm confirmed by a semi-automatic technique of thresholding was applied on pre-processed SAR images to detect temporal changes between pre, peak-and post flood extents.The&nbsp;maximum flood extent&nbsp;was determined using the Maximum Water depth isolines. These were derived on the basis of the observed flood extent and through integrating water level estimations considering the Topographic Wetness Index levels.&nbsp; <br/> <br/>激活日期：2017-12-06 事件类型：洪涝灾害 激活缘由： 本次服务请求的目标为生成参考信息，涉及2017年7月25日至7月27日发生在德国下萨克森州希尔德斯海姆县境内的洪涝事件。本次工作共生成了通用参考内容与土地利用/覆被（Land Use/Cover）产品，以及三类洪涝专项产品：实测洪水范围、最大洪水范围、估算最大洪水范围。 其中，实测洪水范围产品通过对洪涝事件发生期间及灾后的相关合成孔径雷达（Synthetic Aperture Radar，SAR）影像进行适配处理生成。采用经半自动阈值技术验证的分类算法，对预处理后的SAR影像开展分析，以识别洪涝前、峰值期及灾后的地表时序变化差异。 最大洪水范围通过最大水深等值线确定，该等值线基于实测洪水范围，并结合考虑地形湿度指数（Topographic Wetness Index）的水位估算结果整合得到。