Spatiotemporal variation of hydrological connectivity and its threshold effects on flood dynamics: An examination in the arid and semi-arid regions, China

Hydrological connectivity, a critical indicator of underlying surface changes, plays a pivotal role in the generation and evolution of floods. This study focuses on examining hydrological connectivity and its significant impact on flood dynamics. The Hekou-Longmen section (HL) is used as a case area because of its frequent flooding, which is typical of arid and semi -arid zone. By employing the modified hydrological connectivity index ( IC ), this study evaluated the hydrological connectivity and examined its spatiotemporal variation of the HL. Based on 1131 Annual Maximum Instantaneous Streamflow ( AMS ) data of 21 sub -basins in the HL, a panel threshold regression model was used to reveal threshold effect of IC on flood dynamics. The results showed that the annual mean IC showed a decreasing trend, with spatial variation dominated by significant decreases and no change. Furthermore, it was found that the magnitude of the effect of extreme precipitation ( EP ) on AMS increased with increasing IC thresholds. The threshold effect of EP on AMS were found to exist during the 1990s, 2000s, and 2010s, with thresholds of 2.84, 3.27, and 3.37, respectively. This research established a quantitative framework for comprehensively evaluating the impact of underlying surface changes on flood, providing important reference for the study of flood mechanisms in similar arid and semi -arid regions globally.