Assessing the relative contributions of the flood tide and the ebb tide to tidal channel network dynamics

Abstract

Flood and ebb currents provide different contributions to the initiation and evolution of tidal channel networks, generating diverse network structures and channel cross-sections. In order to separate the effects of these contributions, a physical model of a sloping tidal-flat basin was set up in the laboratory. Depending on the degree of tidal asymmetry imposed offshore, either flood or ebb currents can be enhanced. The experimental results show that the ebb current has a higher capability to initiate and shape tidal networks than the flood current. Headward erosion is mainly induced by the ebb flow. The slightly inclined flat surface tends to reduce the energy of the flood current and to enhance the ebb current, thus prolonging the duration of morphodynamic activity as well as sediment motion. Overall, flood-dominated tides favour the formation of small-scale channel branches in the upper basin zone, while long lasting ebb-dominated tides result in more complex, wider and deeper tidal networks.

Evaluating Short-Term Tidal Flat Evolution Through UAV Surveys: A Case Study in the Po Delta (Italy)

“…Usually, the process is caused primarily by tidal currents but, in this study case, creek formation is probably owed to both river floods and ebb currents. The latter exert a greater influence on the morphology than flood tides do [82]. Moreover, this research area is characterised by river floods and ebb tide direction both moving from south to north.…”

Laboratory Experiments of Bank Collapse: The Role of Bank Height and Near‐Bank Water Depth

“…With respect to physical experiments, many studies have been conducted to explore the influence of bank erosion/collapse on the initiation and development of tidal creek networks in response to different factors (Iwasaki et al, 2013) including tidal range (Stefanon et al, 2010) and tidal asymmetry (Geng et al, 2019). For toppling failure in salt marshes, Francalanci et al (2013) and Bendoni et al (2014) stated that the most critical conditions triggering marsh/cliff collapse under the action of wind waves depend on the presence of water inside the tension cracks and low water levels in front of the bank.…”

River, Coastal and Estuarine Morphodynamics Selected papers from the 10th anniversary of the RCEM Symposium

“…At a much larger spatial scale, Geng et al . () use a schematic lagoon to study the initiation and evolution of tidal channel networks. The dynamics and configurations of the synthetic networks show that ebb currents have a higher capability to initiate and shape tidal networks than flood currents.…”

“…The 17 collected contributions include four state-of-science papers concerning the most recent advances in computational morphodynamic modelling of coupled flow-bed-sediment systems (Shimizu et al, 2019), a critical analysis of existing data on vegetation-flow-sediment interactions obtained through both laboratory experiments and field campaigns (Tinoco et al, 2020), a review of existing moving-boundary theories of shorelines with two extensions to allow inclusion of firstorder effects of waves and tides (Voller et al, 2020), and an overall assessment of the role played by wave forcing on the hydro-morphodynamics in shallow nearshore areas and at river mouths (Brocchini, 2019). The other 13 papers cover different topics about morphodynamics, spanning multiple environments, tackling concepts and processes with the aid of refined theoretical and numerical tools (Redolfi et al, 2019;Tambroni et al, 2019), grounding the results on laboratory data (Finotello et al, 2019;Geng et al, 2019;Matoušek et al, 2019, Porcile et al, 2020 and field observations (Fogarin et al, 2019;Tommasini et al, 2019), and making use of interdisciplinary approaches (Calvani et al, 2019;Chen et al, 2019;Pivato et al, 2019;van de Vijsel et al, 2020) also to develop new conceptualizations (Schlömer et al, 2020).…”

“…Increasing supply limitation results in longer and more complex bedform patterns, as revealed by Fourier spectral analysis of the bed morphology. At a much larger spatial scale, Geng et al (2019) use a schematic lagoon to study the initiation and evolution of tidal channel networks. The dynamics and configurations of the synthetic networks show that ebb currents have a higher capability to initiate and shape tidal networks than flood currents.…”