Surface Water Flood Maps (FRM_FH_SURFACE_WATER_VELOCITY_H)

The following probabilities are available for surface water flooding: - High - 10 year return period - Medium - 200 year return period - Low - 200 year return period plus climate change using the UKCP09 high emissions scenario for the 2080s.The surface water hazard maps show (where available): - Flood extent - Flood depth - Flood velocities where appropriate. Velocity is presented, where appropriate; this is determined by considering the confidence in input data, modelling method and impact. It is currently represented as one of four bandsThe climate change scenario has been defined by United Kingdom Climate Projection 2009 (UKCP09) predictions for 2080 high emissions 95%ile predictions. Medium and low probability flood events were selected for consistency with return periods used in Scottish Planning Policy, whereas the high probability was chosen as it is reflective of observed events experienced over the last few decades.地表洪水（surface water flooding）的淹没概率等级如下： - 高概率：对应10年一遇重现期 - 中概率：对应200年一遇重现期 - 低概率：对应叠加2080年代采用英国气候预测2009（UKCP09）高排放情景下气候变化影响的200年一遇洪水。 地表洪水风险图（surface water hazard map）将展示以下可获取的信息： - 淹没范围 - 淹没水深 - 适宜场景下的淹没流速。 流速仅在适宜场景下展示：其展示与否需综合考量输入数据可信度、建模方法及影响效果，当前流速划分为四个等级区间。 本次采用的气候变化情景，基于英国气候预测2009（UKCP09）针对2080年高排放场景的95%分位数预测结果定义。 本次选取中、低概率洪水事件，旨在与苏格兰规划政策（Scottish Planning Policy）中采用的重现期标准保持一致；而高概率洪水事件的选取，则因其可反映近数十年来实际观测到的洪水事件特征。