Modelling the Main Hydrodynamic Patterns in Shallow Water Estuaries: The Minho Case Study

Abstract

Numerical models are key tools to characterize hydrodynamical patterns of coastal environments and anticipate the potential effects of hazardous and extreme events, anthropogenic intervention or climate change. In this work, the openTELEMAC-MASCARET modelling system was selected to represent the dynamics of the Minho estuary, a very shallow estuary located at the Northwestern Iberian Peninsula coast. Calibration and validation results confirm the accuracy of the numerical tool, with small root mean square errors, close to null bias and the close to unit correlation and skill coefficients obtained for water level and currents velocity at several estuarine locations. The obtained results depict a tide dominated estuary with a delay in the tide phase and a marked asymmetry in the tide curve that increases upriver. Additionally, an upstream diminution of M2 and an upstream augmentation of M4 was observed, classifying this estuary as flood-dominated. The represented current patterns show that variations in the intensities of the main driving forces alter the behaviour of the hydrodynamical patterns within the estuary, with a clear dependence on bathymetric and topographic characteristics. During flood events, larger estuarine regions become submerged due to the low margins and the wetland characteristics, highlighting the need for accurate numerical models that can be used as a decision-making support tool for effective and integrated estuarine management.

From Ripples to Large-Scale Sand Transport: The Effects of Bedform-Related Roughness on Hydrodynamics and Sediment Transport Patterns in Delft3D

“…In each of the cases with a spatio-temporally constant Chézy value, the bedforms will not affect the flow anymore, but k s,r is still calculated and affects the sediment transport (see Equation (8)). In each case, the Chézy coefficient is an input for the bed shear stress calculation, which in turn affects the flow.…”

“…Bedform roughness predictions are often a function of bedform dimensions, either height and length [4] or only bedform height [3], which are predicted based on wave-and/or current velocities and median grain size [3,5]. In the case of a spatio-temporally constant parameters, a Chézy value (e.g., [6][7][8]), Manning's n value (e.g., [9]) or a constant roughness based on measured ripple heights (e.g., [10,11]) can be used. In numerical models, the hydrodynamic roughness is often used as a calibration parameter to minimize mismatch in observed and predicted water levels, current velocities or even morphological predictions (e.g., [12]).…”

Hydro- and Morphodynamic Impacts of Sea Level Rise: The Minho Estuary Case Study

“…The Minho is an international river that rises at the Serra de Meira, in Spain, and reaches the Atlantic Ocean between Caminha (Portugal) and La Guardia (Spain) after 340 km, constituting a natural border between the northern Portuguese and Galician regions in its last 70 km (Figure 1). This river plays an important role in hydropower production, tourism, and wine production, and its estuary presents a large diversity of habitats due to its good ecological quality, being a reference in ecotoxicological studies and an example for the implementation of water directives in other rivers [16,17]. In the estuarine area, there is a ferryboat that connects the riverside cities of Caminha and La Guardia, whose operation is conditioned by water level oscillations (dependent on tides, sea level, and river flow) and by the morphodynamics of the estuary (Figure 2).…”

“…The lower estuary presents an accentuated enlargement which results in a decrease of the velocity of the current, creating favorable conditions for sediment deposition. Siltation is one of the main problems of this estuarine region [17]. The annual average temperature of the water is 14 • C [20].…”

Validation of the EROSION-3D Model through Measured Bathymetric Sediments

“…Different types of factors affecting water erosion, such as the climate, topography, soil structure, vegetation and anthropogenic activities, tillage systems and soil or conservation measures [18], can result in different values of sediment generation and deposition as well. Among the factors mentioned above, rainfall intensity and the runoff rate are the major triggers of splash and sheet erosion [19], together with the human activities in rivers, causing changes in the magnitude and nature of material inputs to estuaries, which can trigger erosion with consequences for populations and ecosystems [20].…”