Sponsor
This work is financially supported by the Natural Science Foundation of China (Nos. U24A20181; 42476162; 42376168; 42476215; 42206169). We extend our appreciation to Prof. Amir AghaKouchak (University of California Irvine) and Prof. Wu Hui (East China Normal University) for their comments during the conceptual development.
Published In
AGU Advances
Document Type
Article
Publication Date
6-24-2026
Subjects
Tidal River Flood Risk, Tidal Rivers -- China
Abstract
Tidal rivers are defined as the tide‐influenced, salinity‐free inland reaches of estuaries. Understanding the occurrence of peak water levels (PWLs) is critical for flood risk management, yet the timing and magnitude of PWLs in tidal rivers have been little studied. We address this gap by investigating PWLs during two catastrophic floods (1954 and 2020) in the tidal Yangtze River, which reveals that PWLs are higher during perigean spring tides under intermediate discharges following peak flow. Three factors modulate the PWLs in tidal rivers: river‐enhanced tidal damping, flow‐elevation hysteresis that raises the falling flow limb of the hydrograph, and low‐frequency subharmonics. The latter, arising from nonlinear river‐tide interactions, are distinct in tidal rivers and culminate under intermediate river flow as a result of the balance between tidal energy dissipation and the spectral energy transfer to subharmonics. They elevate PWLs by up to 0.3 m during perigean spring tides in the Yangtze case and amplify compound flood risk. Channel degradation has reduced tidal damping compared with circumstances in the 1950s, resulting in larger tidal ranges and record‐breaking PWLs during the 2020 flood despite a smaller peak discharge. We identify tidal rivers spanning over 3,380 km in worldwide estuaries and deltas, where prevalent subharmonics like MSf are up to 0.65 m in amplitude. Many of those experience even larger tidal amplification due to channel deepening, implying escalating flooding risk under sea‐level rise and human impact. These findings underscore a need to include nonlinear river‐tide interactions in flood risk assessment for river‐coast transition zones.
Rights
Copyright (c) 2026 The Authors
This work is licensed under a Creative Commons Attribution 4.0 International License.
Locate the Document
DOI
10.1029/2025AV002247
Persistent Identifier
https://archives.pdx.edu/ds/psu/44905
Citation Details
Guo, L., Devlin, A. T., Hoitink, T., Townend, I., Jay, D. A., Wang, Z. B., Zhu, C., Moftakhari, H. R., He, Q., Xu, F., Wan, Y., Xu, Y., & Xie, W. (2026). Tidal River Flood Risk Highest During Intermediate Rather Than Peak River Discharge. AGU Advances, 7(3). Portico. https://doi.org/10.1029/2025av002247