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

森林和洪水的科学陷入了冲突，迫切需要根据不断变化的气候，昆虫流行，伐木和砍伐森林进行重新评估。我们对森林和洪水关系的科学认识是先入为主的，几十年的成对流域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挑战，因为一个不适当的实验设计因素的基本配对流域研究方法。数十年的配对流域研究重点关注在同等气象或风暴输入的情况下，收割前和收割后洪水之间的量级变化。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频率的变化，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、森林采伐或毁林改变了洪水的形成过程，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的高度非线性联系，它们应该同时进行评估。这是最好的，通过一个高峰流量频率分布的框架，而不是方差和协方差分析，传统上进行了几十年的森林水文文献。指导森林与洪水关系的研究调查的两个不可分割的问题是：对于具有感兴趣的频率（量级）的洪水事件，量级（频率）的变化是什么？这样的调查需要一个频率配对事件分析，流域的水文响应的利益是整个洪水频率分布。我们结合联合收割机实地调查与数值模拟，重新评估我们的科学观念的森林和洪水的关系，使用新的实验设计配对洪水事件的频率相等。这项分析正在广泛的流域规模，水文气候制度和造林系统进行。

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.