From chronology to frequency pairing: a paradigm shift in the science of forests and floods

从年代学到频率配对：森林和洪水科学的范式转变

• 批准号: 194388-2011
• 负责人: Alila, Younes
• 金额: $ 1.38万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2013
• 资助国家: 加拿大
• 起止时间: 2013-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=523187
• 关键词: chronology; frequency; pairing; paradigm; shift

The science of forests and floods is embroiled in conflict and is in urgent need of reevaluation in light of changing climates, insect epidemics, logging, and deforestation. Our scientific perception of the forests and floods relation is preconceived by further reaffirmed by decades of paired watershed studies. However, the outcomes of these studies had recently been challenged because of an inappropriate experimental design factor fundamental to the paired watershed study approach. Decades of paired watershed studies focused on investigating a change in magnitude between pre- and post-harvesting floods when paired by equal meteorological or storm input. This type of chronological event pairing fails to account for the changing frequency of peak flows caused by harvesting and as a result strips a critical part of the physics from the science of forests and floods. Forests, forest harvesting or deforestation alters processes generating floods in ways that change not only the magnitude of a flood but also its frequency. Due to the highly nonlinear linkage between these two attributes of a flood event they should be evaluated simultaneously. This is best done via the framework of a peak flow frequency distribution and not the analysis of variance and covariance, as traditionally conducted in decades of forest hydrology literature. The two inextricably linked questions that should guide a research investigation of the forests and floods relation are: What is the change in magnitude (frequency) for a flood event with a frequency (magnitude) of interest? Such investigation requires a frequency-paired event analysis, where the watershed's hydrologic response of interest is the entire flood frequency distribution. We combine fieldwork with numerical modelling to re-evaluate our scientific perception of the forests and flood relation using the new experimental design of pairing flood events by equal frequency. The analysis is being conducted across a wide range of watershed sizes, hydro-climate regimes, and silvicultural systems.

森林和洪水科学卷入了冲突，鉴于气候变化、昆虫流行、伐木和森林砍伐，迫切需要重新评估。我们对森林与洪水关系的科学认识是先入为主的，数十年的配对流域研究进一步证实了这一点。然而，由于配对分水岭研究方法的基础实验设计因素不适当，这些研究的结果最近受到了挑战。数十年的配对流域研究重点是调查当气象或风暴输入相同时，收获前和收获后洪水之间的幅度变化。这种按时间顺序排列的事件配对无法解释由采伐引起的峰值流量的频率变化，因此剥夺了森林和洪水科学中物理学的一个关键部分。森林、森林采伐或森林砍伐改变了洪水产生的过程，不仅改变了洪水的强度，还改变了洪水的频率。由于洪水事件的这两个属性之间存在高度非线性联系，因此应同时对它们进行评估。这最好通过峰值流量频率分布的框架来完成，而不是像数十年的森林水文学文献中传统的那样进行方差和协方差分析。指导森林与洪水关系研究的两个密不可分的问题是：具有感兴趣的频率（幅度）的洪水事件的幅度（频率）变化是多少？此类调查需要频率配对事件分析，其中感兴趣的流域水文响应是整个洪水频率分布。我们将实地考察与数值建模相结合，利用相等频率配对洪水事件的新实验设计，重新评估我们对森林和洪水关系的科学认知。该分析正在广泛的流域规模、水文气候状况和造林系统中进行。