New Proposal for maximum hydrological events fitting showing the ‘separation phenomenon’ with flexible TCEV Distribution

作者：Javier Valdés-Abellán, Liangyu Ta, Chen Yu · 年份：2026 · DOI：10.5194/egusphere-egu26-1449 · 研究领域：Hydrology and Drought Analysis、Flood Risk Assessment and Management、Hydrology and Watershed Management Studies

Hydrological extreme records in many regions in the world may include observations from different genesis and levels of extremeness forming a characteristic “separation phenomenon’ that limits the effectiveness of traditional distributions such as the Gumbel and log-Pearson Type III models, and in such mixed extreme populations, the Two-Component Extreme Value (TCEV) distribution is better suited. However, conventional fitting approaches tend to emphasize the abundant ordinary data because of the scarcity of right-tail observations, which results in inaccurate predictions of high quantiles. Nevertheless, accurate representation of the upper tail (i.e., the high-value ranges of the cumulative distribution function, CDF) is essential for flood risk evaluation and the design of hydraulic structures. To address this issue, this study introduces a new TCEV fitting approach (SR-MWS) aimed at improving right-tail performance. In the new proposal, the dataset is first approximated using a piecewise two linear regression, and the slope ratio between the two parts (R = S1/S2) is used to assess whether TCEV modeling is appropriate or not (if R > 1.5, the dataset is regarded as suitable for TCEV fitting). Following, three weighting strategies—linear, quadratic, and exponential—are applied sequentially to obtain the final TCEV parameters. A partitioned scoring framework is then used to select the most suitable weighting scheme, emphasizing the mid-to-upper CDF range F(x) ∈ [0.6, 1.0], ...