Patterns and Causes of Flood Timing Trend (1980–2019) across the Global River Network

Abstract:

Changes in flood seasonality can threaten the finely tuned water resource management systems and, if poorly understood, can alter flood risks in unpredictable ways. Nevertheless, patterns and causes of global flood timing trend remain elusive despite numerous existing efforts on flood magnitude and frequency. It is also largely unknown whether climate change has played a role in shifting flood timing.

Here we obtained an unprecedented set of discharge records from tens of thousands of global gauges and model-reconstructed naturalized discharge at ~3 million river reaches to delineate flood timing trend (1980–2019) across the global river network. We found that the flood timing has been significantly earlier over the southeastern United States, the Amur River Basin, the Amazon River Basin, and large parts of the high-latitude Northern Hemisphere. Significant later floods are observed over the Yangtze River Basin, the lower Congo, and the southeast Asia. To investigate causes of these trends, global daily precipitation, soil moisture, and air temperature data were used to see which factors (i.e., maximum precipitation, antecedent soil moisture, and snowmelt timing) dominate the driving force. This work complements previous studies with a global perspective, and results from this work can be used to disentangle climate change signals on floods.