Variability of annual peak flows in the Beijiang River Basin, South China, and possible underlying causes

Peak flows are the most important flood parameter which relatively reflects the highest level and potential destructive power of a flood. Understanding peak flow changes can effectively capture a flood characteristic and is essential for developing flood control strategies. This study aims to reveal how regional peak flows evolved in recent decades, mainly from a non-linear perspective. The Beijiang River Basin (BRB) was chosen for the analysis, and hydrological data from four hydrologic stations were used. Methods including ensemble empirical mode decomposition and rescaled range analysis were applied to advance the research. Results indicate a non-significant uptrend and a multiple periodicity of peak flows in BRB. However, short periods were more distinct than long ones. In the future, peak flows may continue to increase over time. Such changes in peak flows are possibly due to local reservoir operations and the changing South Asian Summer Monsoon (SASM). The research suggests an increasing flood risk and recommends more regional flood adaptations to avoid flood losses for BRB. Synchronously, it provides a reference for studies regarding periodicity and the future trend of peak flows in other regions.