Dataset Direct Download Service (WFS): Hazard zones of the flooding zone by hydraulic and hydrogeomorphological approach from Sarsonne to Ussel in Corrèze

L_ZI_SARSONNE_2001_ALEAS_S_019 The study determined the flooding areas of the Sarsonne at Ussel by hydrogeomorphological approach on the upstream and downstream areas of the urbanised part (maximum right-of-way only). The hydrogeomorphological approach is a naturalistic approach based on reading the morphology of the alluvial plain. It is supplemented here by extrapolation of the water line from a flood known to establish the reference flood water line. This reading of the morphology of the alluvial plain has been clarified on the urbanised area, thanks in particular to topographical works, allowing the definition of heights and flow rates in the crossing of the urbanised area. The flooding zone was determined by calculating the water line of a centennial flood (reference) determined by extrapolation of the 1994 flood water line, extrapolation based on topographical knowledge, the difference in flows between the 1994 event and a centennial event. Topographic knowledge has been used to determine water heights (between 0 and 1 m and > 1 m); flow velocities were defined qualitatively from valley morphology primarily. The crossing of these two parameters allowed to map the hazard (strength = H > 2 m or 1 m < H < 2 m and V > 0.5 m/s or 0 m < H < 1 m and V > 1 m/s; mean = 1 m < H < 2 m and V < 0.5 m/s or 0 m < H < 1 m and 0.5 m/s < V < 1 m/s; low hazard 0 m < H < 1 m and V < 0.5 m/s).L_ZI_SARSONNE_2001_ALEAS_S_019 本研究针对法国于塞勒（Ussel）境内的萨尔松河（Sarsonne），以其建成区上下游河段（仅按最大通行用地范围为界）为研究对象，采用水文地貌学方法（hydrogeomorphological approach）划定洪水淹没范围。水文地貌学方法是一种基于解读冲积平原（alluvial plain）形态的自然主义研究方法，本研究通过基于已知洪水事件的水位线（water line）开展外推（extrapolation）以确定基准洪水水位线，以此补充该方法的应用。 得益于地形测绘工作（topographical works），建成区段的冲积平原形态解读得到进一步明晰，由此可确定该河段穿城段的水深与流量。 本次洪水淹没范围的划定，通过计算作为基准的百年一遇洪水（centennial flood）的水位线实现：该水位线以1994年洪水水位线为基础，结合地形资料以及1994年洪水事件与百年一遇洪水的流量差值开展外推得到。 研究借助地形资料确定了水深分级（0~1m、>1m），并主要基于河谷地貌（valley morphology）定性确定了流速分级。结合水深与流速两个参数，可绘制洪水危险性分布图：高危险性等级判定为H>2m，或1m<H<2m且V>0.5m/s，或0m<H<1m且V>1m/s；中危险性等级判定为1m<H<2m且V<0.5m/s，或0m<H<1m且0.5m/s<V<1m/s；低危险性等级判定为0m<H<1m且V<0.5m/s。