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

L_ZI_SARSONNE_2001_LIM_L_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_LIM_L_019

本研究针对于塞尔（Ussel）的萨尔松讷河（Sarsonne），采用水文地貌学方法（hydrogeomorphological approach）对其城市化河段的上下游区域（仅考虑最大用地红线范围）开展洪水淹没范围划定工作。水文地貌学方法是一种基于冲积平原（alluvial plain）形态解读的自然主义研究路径，本研究在此基础上，通过对已知洪水的水位线进行外推，以此确定基准洪水水位线。

得益于地形测绘工作的辅助，本次研究针对城市化区域的冲积平原形态解读得到进一步明晰，由此得以确定该区域内河道过水的高度与流量参数。本次研究通过对1994年洪水水位线进行外推，并结合1994年洪水与百年一遇洪水的流量差值、地形测绘数据，确定了作为基准的百年一遇洪水水位线，进而划定洪水淹没范围。

研究依托地形数据确定了洪水水深（分为0至1米、大于1米两类）；流速则主要依据河谷形态进行定性界定。结合水深与流速两个参数，可对洪水灾害风险进行分级：高风险区为水深H>2米且流速V>0.5m/s，或0<H<1米且流速V>1m/s；中风险区为1<H<2米且流速V<0.5m/s，或0<H<1米且0.5m/s<V<1m/s；低风险区为0<H<1米且流速V<0.5m/s。