Industrial projects in hydraulics and hydro-environmental engineering

Knaapen, M. (2022) Industrial projects in hydraulics and hydro-environmental engineering. In: 39th IAHR World Congress, 19-24 June 2022, Grenada, Spain.

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Historically, coastal engineering sediment transport models can be divided into short-term small-scale storm response models and one-line models to simulate long-term large-scale coastal changes. Only relatively recently large scale sediment transport models have become more relevant for engineering project, proving an intermediate between the two, modelling detailed processes over longer length- and timescales. HR Wallingford have started using large-scale coastal models commercially in the past 5 years. With the advancement of high performance computing, these area models are becoming ever larger, modelling shorelines up to hundreds of kilometre. These projects have shown that large scale modelling of sediment transport and morphodynamics adds value. It helps to deal with complex situations; provides detailed information over large areas; and has shown to change the perception on the mechanisms driving coastal change in specific locations. Area models simulate the complex interactions between winds, waves and currents on the sediment transport. Waves currents and sediment transport are computed fully coupled at a time scale of seconds to minutes over periods of years, sometimes using a morphological factor to increase the simulation period to up to 20 years. The mesh resolutions at the shoreline were about 10m, increasing to 5km elements offshore. The models are driven by water levels, currents and wave spectra on the boundary and spatially varying wind fields over the domain. Boundary conditions were taken from global models: e.g TPXO/HYCOM for currents ERA5 for waves). The modelling showed some requirements. It is necessary to put the offshore boundary well away from the shoreline of interest, in one case in the English Channel even about 100km away, to eliminate errors due to the poor resolution of the driver models. Spectral wave boundary condition can be important even if the sediment transport predictors use monochromatic wave input. Primarily, this is due to our inability to objectively determine in advance which wave period will be dominating the nearshore sediment transport. For a nourishment project, area modelling provided offshore losses to calibrate a 1-line model. Although the area modelling does not account for cross-shore processes in the breaker zone, it does provide reliable estimates of cross-shore processes around the depth of closure for wave driven transport. The 1-line model was then used for the nourishment option analysis. Finally, the preferred option was verified with the area modelling. Elsewhere, the modelling provided stark warning about the necessity of a long groyne protecting a soft-cliff headland. The area model identified clear transport pathways due to the currents with wave stirring, often in the opposite direction of the wave driven littoral drift, explaining unexpected losses of sediments and disappearing nourishments. In summary, area modelling provides a valuable tool for coastal engineers next to the storm response and shoreline models.

Item Type: Conference or Workshop Item (Paper)
Subjects: Maritime > General
Divisions: Maritime
Depositing User: Helen Stevenson
Date Deposited: 11 Apr 2022 08:46
Last Modified: 10 Jun 2022 12:27

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