Propensity of rivers to extreme floods:climate-landscape controls and early detection (PREDICTED)

河流发生极端洪水的倾向：气候景观控制和早期发现（预测）

• 批准号: 421396820
• 负责人: Dr. Larisa Tarasova, since 10/2022
• 金额: --
• 依托单位: Department Catchment Hydrology
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/421396820?language=en
• 关键词: Propensity; rivers; extreme; floods; climate

The occurrence around the world of several major river floods in a short period of time, pictured by sharp upward deviations (called step changes) of the curves used to assess how large floods can be and how often they will occur (called flood frequency curves), recently led citizens, engineers and scientists to wonder whether floods have changed. This is an important issue for social endeavors and economic sectors which require trustworthy evaluations of the flooding hazard of river basins, such as urban planning, the management of water resources and the insurance industry. Alterations of the climate and loss of soil storage due to human activities (e.g. intensive agriculture and urbanization) are often claimed to trigger these phenomena. However, the normal functioning of river basins might also cause floods that appear as extreme because they were not yet recorded in the available data series.The project aims to ascertain whether the interactions between climate and landscape of river basins are able to produce extreme floods, also when no changes of the external drivers (e.g. rainfall) occur. Moreover, it aims to provide handy methods to assess this possibility based on features that can be characterized also in areas where extreme events have not been observed yet and long records of floods are not available. Methods to detect in an objective way the beginning of distinct rises of observed and modeled flood frequency curves (i.e. the position of step changes) will be developed. After verifying that step changes may be more than mere mathematical fakes due to the limited length of the available data, and that modifications of rainfall or land use are not necessarily required for having step changes, attributes of river basins linked to their appearance will be investigated. The focus will be placed on climatic and landscape features that have been suggested as relevant for streamflow generation by a recently proposed simplified description of the processes taking place within river basins. An index which summarizes how these features interact to produce (or not) step changes will be derived. The capability of this index to predict the position of the step change will be tested against observations in a large set of river basins from different geographical regions. The possibility to adopt the step change as a divide between normal and extreme floods will be evaluated as well. The ultimate objective of this project is the development of charts describing the reliability of observed time series for assessing flood hazard in river basins subject to different climatic and landscape settings, or the required length of monitoring to obtain trustworthy estimates of floods. Modifications to these indications of practical interest recommended as a consequence of climate change will be also provided by means of scenarios.

世界各地在短时间内发生了几次主要河流洪水，用于评估洪水可能有多大以及发生频率的曲线（称为洪水频率曲线）急剧向上偏离（称为阶跃变化），最近导致公民，工程师和科学家怀疑洪水是否发生了变化。这对于城市规划、水资源管理、保险业等社会事业和经济部门来说是一个重要课题，需要对流域的洪水灾害进行可靠的评估。气候的变化和人类活动（如集约化农业和城市化）造成的土壤贮量损失往往被认为是引发这些现象的原因。然而，河流流域的正常运作也可能造成极端的洪水，因为它们尚未记录在现有的数据系列中，该项目旨在确定气候与河流流域景观之间的相互作用是否能够产生极端的洪水，即使在外部驱动因素（如降雨）没有发生变化的情况下。此外，它的目的是提供方便的方法来评估这种可能性的基础上，也可以在极端事件尚未观察到和长期的洪水记录不可用的地区的特点。将开发以客观方式检测观测和模拟洪水频率曲线（即阶跃变化的位置）明显上升的开始的方法。在验证了阶跃变化可能不仅仅是由于可用数据的长度有限而造成的数学假现象，以及降雨量或土地利用的修改不一定需要阶跃变化之后，将调查与其外观相关的河流流域属性。重点将放在气候和景观特征，已建议有关的河流流域内发生的过程，最近提出的简化描述的流量生成。一个指数，总结这些功能如何相互作用，以产生（或不）步骤的变化将被派生。该指数预测阶跃变化位置的能力将根据来自不同地理区域的大量河流流域的观测结果进行测试。还将评估采用阶跃变化作为正常洪水和极端洪水之间分界线的可能性。该项目的最终目标是绘制图表，说明观察到的时间序列的可靠性，以评估受不同气候和地貌环境影响的河流流域的洪水危害，或说明为获得可靠的洪水估计数所需的监测时间。由于气候变化而建议对这些具有实际意义的指标进行的修改，也将通过设想情景的方式提供。