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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
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Advisor(s)
Abstract(s)
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.
Description
Keywords
Seasonal behaviour Water