Modeling analysis of tidal bore formation in convergent estuaries

Abstract

Despite the recognized impact of tidal bores on estuarine ecosystems, the large scale mechanism of bore formation in convergent alluvial estuaries is still under investigation. So far, field data exist only for a small number of estuaries, while numerical simulations employ the shallow water equations mainly focusing on the small-scale and local processes. In this work, firstly we apply the fully nonlinear weakly dispersive Serre-Green-Naghdi equations to simulate the tide propagation in a convergent estuary of idealized form, verifying that the local dispersion effects, responsible for the appearance of the secondary waves, do not influence the tidal bore onset, which only results from the large scale processes of amplification/damping and distortion of the incoming wave. In

Introduction to the Special Issue on Breaking Waves

“…It is shown that these events become phase-locked in the presence of waves. The contribution by Filippini, Arpaia, Bonneton and Ricchiuto [97] contains a study of the formation of river bores detailing the numerical aspects behing the physical results discussed in [14]. The authors define certain parameters based on the estuary geometry the water depth, the amplitude and the angular frequency of the tidal wave.…”

Consideration of the Mechanisms for Tidal Bore Formation in an Idealized Planform Geometry

“…Among the many mechanisms and conditions that affect the process of tidal bore formation, the more relevant are (i) the rate of tidal level rise (e.g., Bonneton et al, 2016;Chanson, 2011b), (ii) the characteristics of the incoming flow, typically flow depth and velocity (e.g., Cai et al, 2014;Filippini et al, 2018), (iii) the funneling shape of the estuary that deforms the tidal wave by steepening the rising limb, hence enhancing the rate of level rise (e.g., Friedrichs & Aubrey, 1994;Lanzoni & Seminara, 1998;Savenije, 2012;Toffolon et al, 2006), (iv) the channel bed profile that also affects the characteristics of the propagating tidal wave (e.g., Cai et al, 2012;Savenije et al, 2008;Shi et al, 2014), and (v) the irregular shape of cross sections, which may introduce additional dissipative processes, alter the wave celerity, and produce reflections and/or distortions of the bore front (e.g., Bonneton et al, 2011;Pan et al, 2007;Shi et al, 2014;Treske, 1994).…”

“…Among these mechanisms and processes, some are necessary for a bore to form (e.g., the rise of downstream water level), whereas others just act to promote and enhance the bore formation (e.g., the funneling shape; Filippini et al, 2018). In fact, tidal bores can also form in straight channels (e.g., the tidal bore on the River Winster, UK) and are often studied using straight flumes with rectangular or trapezoidal cross section, constant width and bed slope (Chanson, 2009(Chanson, , 2010Hayami et al, 1955;Koch & Chanson, 2008;2009;Favre, 1935;Prüser & Zielke, 1994;Treske, 1994).…”

Tidal bore impact pressures on a trestle pier in the Qiantang River Estuary, China

“…40 The tide is a periodic fluctuation phenomenon caused by the gravitational pull of the moon, the sun, and other celestial bodies on the ocean surface, and the tidal bore is at the front of the tidal wave. 41,42 Therefore, the occurrence of tidal bores is predictable to a certain extent. 43 The interaction between the tidal bore and the structures can be observed by installing well-spaced sensing equipment.…”