Simple download service (Atom) of the dataset: Isocotes of the flooding zone by hydrogeomorphological approach of the Sarsonne River, municipality of Ussel en Corrèze

L_ZI_SARSONNE_2001_ALEAS_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_ALEAS_L_019

本研究采用水文地貌学方法（hydrogeomorphological approach），针对城市化河段的上下游区域（仅统计法定最大河道用地范围内区域），确定了于塞勒（Ussel）境内萨尔松讷河（Sarsonne）的洪水淹没范围。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，本次研究通过对已知历史洪水的水位线进行外推以建立基准洪水水位线，以此补充完善该方法。

得益于地形测绘工作的支持，城市化区域内的冲积平原形态解读得到了进一步明晰，由此得以确定城市化河段过流时的水位高度与流量速率。洪水淹没区域通过推算百年一遇洪水（centennial flood，基准事件）的水位线得以确定：该基准水位线由1994年洪水的水位线结合地形知识，通过1994年洪水事件与百年一遇洪水事件的流量差值外推得到。

研究借助地形知识确定了水位高度区间（0~1米、>1米）；流量流速则主要依据河谷形态进行定性界定。结合上述两个参数，研究完成了洪水风险等级的分级制图：高风险（H>2米或1米<H<2米且流速V>0.5m/s，或0米<H<1米且V>1m/s）；中风险（1米<H<2米且V<0.5m/s，或0米<H<1米且0.5m/s<V<1m/s）；低风险（0米<H<1米且V<0.5m/s）。