Dataset Direct Download Service (WFS): Speeds in the flood zone by hydraulic and hydrogeomorphological approach from Sarsonne to Ussel in Corrèze

L_ZI_SARSONNE_2001_V_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_V_S_019

本研究针对于塞勒地区萨尔松河城市化河段的上下游区域（仅采用最大河道用地红线范围），采用水文地貌学方法（hydrogeomorphological approach）确定其洪水淹没范围。该方法是一类以冲积平原（alluvial plain）形态解析为核心的自然主义研究路径，本次研究通过基于已知洪水事件推衍得到的水位线，补充该方法以确定基准洪水水位线。

针对城市化区域的冲积平原形态解析工作，借助地形测绘成果得到了明确细化，由此得以确定该区域内的水深与流速参数。本研究通过推衍1994年洪水水位线，结合地形勘测数据以及1994年洪水事件与百年一遇洪水（centennial flood）事件的流量差值，计算得到百年一遇基准洪水的水位线，进而确定淹没范围。

研究借助地形数据划定水深等级（0~1米、>1米）；流速则主要基于河谷形态进行定性划分。结合上述两类参数，可完成洪水危险性制图，分级标准如下：高危险等级：水深H>2米，或1米<H<2米且流速V>0.5m/s，或0米<H<1米且流速V>1m/s；中危险等级：1米<H<2米且流速V<0.5m/s，或0米<H<1米且0.5m/s<V<1m/s；低危险等级：0米<H<1米且流速V<0.5m/s。