Isocote lines of the flood prevention plan (PPRI) of the river “La Vienne” downstream, Antran sector in Port-de-Pile

The isocote lines (curves of altitude levels reached by the waters during the centennial flooding) constitute a series of geographical data produced as part of the Vienna Downstream Flood Risk Prevention Plan. Isocotes are reported on hazard maps and reference ratings on regulatory maps. The reference rating is the isocote plus 20 cm. This reference rating is applied during certain adjustments. That is, at any point in the flood zone defined on the hazard map, when a development is carried out, the rating to be respected for the development is the reference rating. This can be calculated at any point in the flood zone, by linear interpolation between the different isocote lines.等水位线（isocote lines，即百年一遇洪水时水体抵达高度的等值曲线）作为维也纳下游防洪风险规划的配套产出成果，构成了一套地理数据集。 等水位线会标注于洪水风险地图中，基准限值则标注于管控地图内。该基准限值为等水位线数值加20厘米，且会在部分调整工作中应用。具体而言，在风险地图划定的洪泛区内，若开展建设开发活动，需遵守的建设限值即为该基准限值。该基准限值可通过洪泛区内不同等水位线间的线性插值法，在洪泛区任意点位计算得出。