Research on design rainfall patterns of typical river basins in Guangdong Province based on fuzzy clustering soft partition method

Abstract

[Objective] Designing rainfall patterns serves as a crucial component in calculating design floods for ungauged basins, significantly influencing peak flow rates and temporal distribution of design floods. Given the impacts of climate change, existing rainfall patterns may alter, necessitating the extension of hydrology data to further investigate these changes. [Methods] This study adopts the Mann-Kendall trend test and fuzzy clustering soft partition method, selecting 12 rainfall stations within four typical watersheds in Guangdong Province, focusing on their annual maximum 24-hour and 72-hour rainfall processes. Based on an index system, a fuzzy equivalence matrix is constructed, and the design rainfall patterns under different durations are derived using fuzzy clustering. [Results] The results indicate that annual maximum 24-hour and 72-hour rainfall in the Dongguan River Basin exhibits an increasing trend, with Baimang meteorological station showing the highest rate of change at 0.96 mm/a for annual maximum 24-hour rainfall. Conversely, a decreasing trend is observed in the Rongjiang North River Basin, with Fukou meteorological station experiencing a rate of change of-1.25 mm/a for annual maximum 72-hour rainfall. Furthermore, the design rainfall patterns in all typical basins exhibit composite peak characteristics, with no significant difference in the proportion of the main rain peak in total rainfall. The primary difference lies in the temporal distribution of rainfall. [Conclusion] Compared with the design rainfall patterns outlined in the “Rainstorm Runoff Calculation Chart Manual of Guangdong Province”, the control period of the main peak was shifted. This research not only provides valuable references for design flood calculations in typical watersheds but also offers insights into the study of rainstorm patterns in ungauged regions.

Keywords

Guangdong Province / fuzzy clustering soft partitioning method / rainfall / Mann-Kendall trend test / design rain pattern / climate change / rainstorm pattern in areas without data / flood forecast