Flood — Awareness — Overland Flow

This dataset, created in June 2013, provides an indication of the likelihood of a flood occurring from overland flow inside the Brisbane City Council local government area. This layer contributes to the overall Flood Awareness Mapping for Brisbane City Council. Overland flow is excess rainfall that runs across the land after rain before it enters an underground drainage system or a creek/waterway. Overland flow can also rise to the surface naturally from underground or also as a result of creek/waterway bank failure. Overland flow flooding tends to affect localised areas rather than the whole city at once. Overland flow can probably be considered the most frequent type of flooding in Brisbane. Overland flow tends to occur during high rainfall events. It travels across the land following low-lying, natural drainage paths. Such flooding may occur when underground drainage system exceeds capacity. Overland flow flooding can be unpredictable and occur without warning. You can identify overland flow by looking at how water may flow across the land around your property. Consider these natural flows when you are looking to renovate, build a fence or put in a shed. There are three different overland flow flooding impact areas in Flood Awareness Map, namely High, Medium and Low. The overland flow High impact layer consists of H5 and H6* hazard zones during a 5% Annual Exceedance Probability (AEP) (20 year Average Recurrence Interval (ARI)) flood event. The flood data was sourced from the Citywide Creek and Overland Flow Path mapping study (GHD, 2017). The overland flow Medium impact layer consists of H3, H4, H5 and H6* hazard zones during a 2% AEP (50 year ARI) flood event (outside high impact area). The flood data was sourced from the Citywide Creek and Overland Flow Path mapping study (GHD, 2017). The overland flow Low impact layer consists of H2, H3, H4, H5 and H6* hazard zones during a 1% AEP (100 year ARI) flood event (outside high and medium impact areas). The flood data was sourced from the Citywide Creek and Overland Flow Path mapping study (GHD, 2017). * Hazard ranges from H1 to H6 and is based on the flood hazard, depth and velocity vulnerability thresholds. For more information, refer to Australian Disaster Resilience Guideline 7-3 Flood Hazard (AIDR 2017).本数据集于2013年6月编制完成，旨在表征布里斯班市议会（Brisbane City Council）行政辖区内由地表径流引发洪涝的发生概率，是布里斯班市议会全域洪涝预警地图的核心组成部分。地表径流指降雨后，未及汇入地下排水系统或溪流/水道前，于陆地表面漫流的过剩雨水；其亦可由地下水源自然涌出，或因溪流/水道堤岸溃决而浮现于地表。地表径流洪涝通常仅影响局部区域，而非全域城市。该类洪涝可被视为布里斯班最为频发的洪涝类型，多发生于强降雨事件期间，沿低洼地带的自然排水路径在陆地漫流。当地下排水系统超出承载能力时，即可能引发此类洪涝。地表径流洪涝往往难以预测，且可能毫无预警地发生。公众可通过观察物业周边的水流路径识别地表径流情况，在开展翻新作业、修建围栏或搭建棚屋时，应充分考量此类自然水流路径。布里斯班市议会的洪涝预警地图中共设置三类地表径流洪涝影响分区，分别为高、中、低影响区：1. 高影响图层：对应5%年超越概率（Annual Exceedance Probability, AEP）（即20年一遇平均重现期（Average Recurrence Interval, ARI））的洪涝事件中，H5与H6*灾害等级区域，相关洪涝数据源自《全市溪流与地表径流路径测绘研究》（GHD, 2017）；2. 中影响图层：对应2%年超越概率（AEP）（即50年一遇平均重现期（ARI））的洪涝事件中，H3、H4、H5与H6*灾害等级区域（不含高影响区），相关洪涝数据源自《全市溪流与地表径流路径测绘研究》（GHD, 2017）；3. 低影响图层：对应1%年超越概率（AEP）（即100年一遇平均重现期（ARI））的洪涝事件中，H2、H3、H4、H5与H6*灾害等级区域（不含高、中影响区），相关洪涝数据源自《全市溪流与地表径流路径测绘研究》（GHD, 2017）。* 灾害等级划分为H1至H6，基于洪涝灾害强度、水深及流速脆弱性阈值划定，详细信息可参考《澳大利亚灾害韧性指南7-3：洪涝灾害》（AIDR, 2017）。