Print Email Facebook Twitter Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary Title Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: Identifying the critical position and river discharge for maximum tidal damping Author Cai, Huayang (Sun Yat-sen University; Guangdong Provincial Engineering Research Center of Coasts; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai); East China Normal University) Savenije, Hubert (TU Delft Water Resources) Garel, Erwan (University of the Algarve) Zhang, Xianyi (Sun Yat-sen University; Guangdong Provincial Engineering Research Center of Coasts; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai)) Guo, Leicheng (East China Normal University) Zhang, Min (Shanghai Normal University) Liu, Feng (Sun Yat-sen University; Guangdong Provincial Engineering Research Center of Coasts; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai)) Yang, Qingshu (Sun Yat-sen University; Guangdong Provincial Engineering Research Center of Coasts; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai)) Date 2019 Abstract As a tide propagates into the estuary, river discharge affects tidal damping, primarily via a friction term, attenuating tidal motion by increasing the quadratic velocity in the numerator, while reducing the effective friction by increasing the water depth in the denominator. For the first time, we demonstrate a third effect of river discharge that may lead to the weakening of the channel convergence (i.e. landward reduction of channel width and/or depth). In this study, monthly averaged tidal water levels (2003-2014) at six gauging stations along the Yangtze River estuary are used to understand the seasonal behaviour of tidal damping and residual water level slope. Observations show that there is a critical value of river discharge, beyond which the tidal damping is reduced with increasing river discharge. This phenomenon is clearly observed in the upstream part of the Yangtze River estuary (between the Maanshan and Wuhu reaches), which suggests an important cumulative effect of residual water level on tide-river dynamics. To understand the underlying mechanism, an analytical model has been used to quantify the seasonal behaviour of tide-river dynamics and the corresponding residual water level slope under various external forcing conditions. It is shown that a critical position along the estuary is where there is maximum tidal damping (approximately corresponding to a maximum residual water level slope), upstream of which tidal damping is reduced in the landward direction. Moreover, contrary to the common assumption that larger river discharge leads to heavier damping, we demonstrate that beyond a critical value tidal damping is slightly reduced with increasing river discharge, owing to the cumulative effect of the residual water level on the effective friction and channel convergence. Our contribution describes the seasonal patterns of tide-river dynamics in detail, which will, hopefully, enhance our understanding of the nonlinear tide-river interplay and guide effective and sustainable water management in the Yangtze River estuary and other estuaries with substantial freshwater discharge. To reference this document use: http://resolver.tudelft.nl/uuid:b0c6eab7-1fc8-4cb1-98aa-b4c5cf0c742c DOI https://doi.org/10.5194/hess-23-2779-2019 ISSN 1027-5606 Source Hydrology and Earth System Sciences, 23 (6), 2779-2794 Part of collection Institutional Repository Document type journal article Rights © 2019 Huayang Cai, Hubert Savenije, Erwan Garel, Xianyi Zhang, Leicheng Guo, Min Zhang, Feng Liu, Qingshu Yang Files PDF hess_23_2779_2019.pdf 6.06 MB Close viewer /islandora/object/uuid:b0c6eab7-1fc8-4cb1-98aa-b4c5cf0c742c/datastream/OBJ/view