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
本研究针对于塞勒境内的萨尔松讷河，针对其城市化河段的上下游区域（仅涵盖最大通行用地范围），采用水文地貌学方法（hydrogeomorphological approach）划定了该河段的洪水淹没范围。该水文地貌学方法属于基于冲积平原形态解读的自然主义研究方法，本研究中通过从已知洪水事件中推延得到水面线，以此建立基准洪水水面线，对该方法进行了补充。针对城市化区域的冲积平原形态解读，本研究借助地形测绘工作进一步明确了细节，得以确定该城市化过境河段的水位与流量参数。本次洪水淹没范围的划定，是通过对1994年洪水水面线进行推延，结合地形认知以及1994年洪水与百年一遇洪水的流量差值，计算得到基准百年一遇洪水的水面线，以此确定淹没区域。研究通过地形认知确定了水位高程（分为0~1米、＞1米两个区间）；流速则主要依据河谷形态进行定性界定。结合水位与流速这两个参数，可绘制洪水危险性分布图：高危险等级对应条件为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；中危险等级对应条件为1米＜H＜2米且V＜0.5m/s，或0米＜H＜1米且0.5m/s＜V＜1m/s；低危险等级对应条件为0米＜H＜1米且V＜0.5m/s。