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

森林和洪水科学陷入冲突，迫切需要根据气候变化、虫害流行、伐木和森林砍伐进行重新评估。我们对森林和洪水关系的科学认识是先入为主的，几十年的配对分水岭研究进一步重申了这一点。然而，这些研究的结果最近受到了质疑，因为配对分水岭研究方法的基本实验设计因素不适当。几十年来，流域配对研究的重点是调查在气象或风暴输入相等的情况下，收获前和收获后洪水之间的量级变化。这种按时间顺序排列的事件配对不能解释采伐引起的高峰流量的变化频率，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产生洪水的过程，不仅改变了洪水的规模，而且改变了洪水的频率。由于洪水事件的这两个属性之间具有高度的非线性联系，因此应该同时对它们进行评估。这最好是通过峰值流量频率分布的框架，而不是传统上在几十年的森林水文学文献中进行的方差和协方差分析。应该指导对森林和洪水关系的研究调查的两个密不可分的问题是：洪水事件的震级(频率)与感兴趣的频率(震级)的变化是什么？这样的调查需要频率配对的事件分析，其中分水岭的水文响应是整个洪水频率分布。我们将实地调查与数值模拟相结合，使用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。这项分析正在广泛的流域大小、水文气候制度和营林系统中进行。

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.