Flood Extent 200 Year (OpenData)

This entity describes how far floodwaters could spread during a '1-in-200-year flood'. A '1-in-200-year flood' means there is a 0.5% chance of that level of flooding happening in any given year. Similarly, a '1-in-50-year flood' has a 2% chance of occurring in a year. These probabilities are based on long-term weather and tide records. We also adjust the data to account for future changes in rainfall and sea levels due to climate change. To estimate flood areas, we use computer models that simulate how stormwater flows through Christchurch’s drainage system. These models test different rainfall durations—from short bursts (30 minutes) to long storms (up to 60 hours). For each flood scenario, the model calculates the deepest flooding expected, the largest of which becomes the final flood extent shown in the data. This flood extent data is used in a derived model called drvFloodExtent, which combines flood models for all catchments and scenarios and is intersected with Rating Units to generate Property Condition comments on the LIM. Any updates to the flood extent data need to be synced to the derived model to appear on the LIM. It is spatially abstracted to: Area. Entity Type: Event.本数据集描述了“200年一遇洪水”（1-in-200-year flood）情境下洪水的可能蔓延范围。“200年一遇洪水”指任意一年内发生该等级洪水的概率为0.5%；同理，“50年一遇洪水”（1-in-50-year flood）的年发生概率为2%。上述概率基于长期气象与潮汐观测记录推导得出，同时我们还针对气候变化引发的未来降雨与海平面变化对数据进行了修正。为估算洪水淹没范围，本数据集采用计算机模型模拟暴雨径流在基督城排水系统中的流动过程。这些模型会测试不同降雨时长的情境——从短时强降雨（30分钟）到持续长时风暴（最长60小时）。针对每种洪水情境，模型会计算预估的最大积水深度，其中最极端的情境对应的淹没范围即为数据集最终呈现的洪水蔓延范围。该洪水蔓延范围数据将被用于名为drvFloodExtent的衍生模型，该模型整合了所有集水区与情境下的洪水模型，并与评级单元（Rating Units）进行空间叠加分析，以在LIM中生成房产状况相关评论。洪水蔓延范围数据的任何更新都需要同步至该衍生模型，方可在LIM中显示相关结果。该数据集在空间上抽象为：区域。实体类型：事件（Event）。