Map Viewing Service (WMS) of the dataset: Heights of the flooding zone by hydraulic and hydrogeomorphological approach from Sarsonne to Ussel in Corrèze

L_ZI_SARSONNE_2001_H_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_H_S_019
本研究针对于塞勒（Ussel）地区的萨尔松讷河（Sarsonne），采用水文地貌学方法（hydrogeomorphological approach），对城市化河段的上下游区域（仅以法定河道管理范围为准）开展洪水淹没范围划定工作。水文地貌学方法属于一种基于冲积平原形态解析的自然主义研究方法，本次研究通过基于已知洪水事件的水位线外推以确定基准洪水水位线，对该方法进行补充完善。
针对城市化河段的冲积平原形态解析工作，依托地形测绘资料得到了进一步明晰，由此可确定该河段的水深与流量参数。本次洪水淹没范围通过计算百年一遇洪水（基准洪水）的水位线得到，该水位线由1994年洪水水位线结合地形资料、1994年洪水与百年一遇洪水的流量差值进行外推获得。
研究依托地形资料确定水深数据，水深分为0~1米与>1米两个区间；流速则主要基于河谷形态进行定性界定。综合水深与流速两个参数，可划定洪水危险性等级：高危险区为H>2米，或1米<H<2米且流速V>0.5米/秒，或0米<H<1米且V>1米/秒；中危险区为1米<H<2米且V<0.5米/秒，或0米<H<1米且0.5米/秒<V<1米/秒；低危险区为0米<H<1米且V<0.5米/秒。