The selection of flood events and determination of flood characteristics (e.g. start and end dates, peak discharge, volume, and duration) are the first critical steps for flood analyses. To obtain the key flood information accurately, we used the automatic peak over threshold (POT) model for flood sampling and proposed an automatic approach to determine flood characteristics using the master recession curve analysis (MRC) method. We further developed a graphical user interface (GUI) and toolbox for this procedure in MATLAB. Model parameter estimation experiment (MOPEX) data from 423 stations were used to evaluate the proposed method. Our results suggest that the proposed procedure performs well for watersheds with diverse characteristics. The developed toolbox can be conveniently applied to other watersheds for flood sampling and the characterisation of flood events, thus helping reduce the uncertainty in subsequent flood analyses, such as multivariable flood frequency and trend analyses.

洪水事件的选择和洪水特征的确定（例如开始和结束日期、峰值流量、流量和持续时间）是洪水分析的第一个关键步骤。为了准确获取关键洪水信息，我们使用自动峰值超阈值 (POT) 模型进行洪水采样，并提出了一种使用主衰退曲线分析 (MRC) 方法确定洪水特征的自动方法。我们进一步在 MATLAB 中为此过程开发了图形用户界面 (GUI) 和工具箱。使用来自 423 个站点的模型参数估计实验 (MOPEX) 数据来评估所提出的方法。我们的结果表明，所提出的程序对于具有不同特征的流域表现良好。