The historic Yangtze River floods: Role of multiscale storm movement

The Yangtze River Basin (YRB) has repeatedly witnessed devastating, widespread floods. While extensive research has been devoted to understanding the impact of large-scale synoptic conditions and river regulations on these events, the role of storm dynamics has received much less attention; this is also true for a comprehensive comparative analysis among these historic floods, crucial for flood protection. Here, we employ rainfall and flood observations, reanalysis datasets, and large-scale hydrodynamic simulations to revisit the historic Yangtze River floods, with a special focus over middle and lower reaches. We find that these disastrous Yangtze River floods are a product of persistent heavy rainfall during the warm season and anomalously wet antecedent condition. The 1954 flood, for instance, is characterized by anomalous timing of the rainfall peaks, early across the upper reaches and delayed at middle-lower reaches. This leads to synchronized and elevated flood peaks along the main streams. We discern a preferential direction of storm movement for the 1954 flood, aligning perfectly with the river flow along the main tributaries. We will quantify the contributions of storm motion and timing to flooding in the YRB through space-time decomposition and hydrodynamic simulations for several historic flood events.