Interaction between suspended sediment and tidal amplification in the Guadalquivir Estuary

Abstract

Water level records at two stations in the Guadalquivir Estuary (Spain), one near the estuary mouth (Bonanza) and one about 77 km upstream (Sevilla), have been analysed to study the amplification of the tide in the estuary. The tidal amplification factor shows interesting temporal variation, including a spring-neap variation, some extreme low values, and especially the anomalous behaviour that the amplification factor is larger during a number of periods. These variations are explained by data analysis combined with numerical and analytical modelling. The spring-neap variation is due to the quadratic relation between the bottom friction and the tidal flow velocity. The river flood events are the direct causes of the extreme low values of the amplification factor, and they trigger the non-linear interaction between the tidal flow and suspended sediment transport. The fluvial sediment input during a river flood causes high sediment concentration in the estuary, up to more than 10 g/l. This causes a reduction of the effective hydraulic drag, resulting in stronger tidal amplification in the estuary for a period after a river flood. After such an event the tidal amplification in the estuary does not always fall back to the same level as before the event, indicating that river flood events have significant influence on the long-term development of this estuary.

Human impacts on morphodynamic thresholds in estuarine systems

“…In a low-turbidity estuary in which the apparent roughness does not depend on tidal range, the amplitude ratio between an upstream and a downstream station decreases with increasing tidal amplitude due to the quadratic relation between bed shear stress and flow velocity (Wang et al, 2014). Available water level observations in the Yangtze Estuary show that the amplitude at the upstream station Xuliujing is only slightly larger than the downstream station Liuyao during neap tides, and smaller during spring tides (Fig.…”

“…Notice that the amplitude ratio in 2000 (right panel) is lower than in 1997 (left panel). For more details on the analysis method and explanation of the scatters, reference is made toWang et al (2014). human interventions on competing channels for both examples is elaborated below.…”

An Analytical Approach to Determining Resonance in Semi-Closed Convergent Tidal Channels

“…However, only few studies have investigated the evolution of hydrodynamics along the Guadalquivir estuary [e.g. Garcia-Lafuente et al, 2012;Diez-Minguito et al, 2012;Wang et al, 2014]. The two case studies have been chosen to illustrate the performances of the analytical approach because they present similarities in the width convergence ratio, but are characterized by a significantly different response to resonance.…”

“…The latter parameter describes the effective friction, including some factors of difficult quantification, in addition to the usual sediment roughness, like the additional drag resistance due to bed forms, the influence of suspended sediments [e.g. Winterwerp and Wang, 2013;Wang et al, 2014], and the possible effect of lateral storage areas [e.g. Savenije, 2005Savenije, , 2012.…”

Physics of Estuaries and Coastal Seas 2012

“…Their results yield a simple semi-empirical formulation for particle fall velocity that is dependent on turbulent stresses. Wang et al (2014) use observations and modeling to investigate temporal variability in tidal amplification in the Guadalquivir estuary in Spain. Results reveal the expected modulation of tidal amplification by quadratic drag over the spring/ neap cycle and a reduction in amplification during high flow events.…”