A validated numerical model of tidal flows and sediment transport around the Alderney South Banks was used to investigate the potential effects of large (300 MW) tidal turbine arrays at different locations in Alderney territorial waters. Two methods were used, firstly looking at hydrodynamic changes only and secondly modelling sediment transport over a non-erodible bed. The baseline hydrodynamic model was validated relative to ADCP velocity data collected in the immediate vicinity of the sandbank. Real-world sand transport rates were inferred from sand-wave migrations and agree favourably with sediment transport residuals calculated from model outputs. Outputs from the sediment model reproduced realistic morphological behaviours over the bank. Seventeen different locations were considered; most did not result in significant hydrodynamic changes over the South Banks; however, three array locations were singled out as requiring extra caution if development were to occur. The results provide a case for optimizing the array locations for twin objectives of maximizing array power and minimizing impacts on the sandbanks. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

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潮汐力对附近沙洲的影响：奥尔德尼岛竞赛的案例研究

奥尔德尼岛南岸周围潮汐流和泥沙输送的经过验证的数值模型用于研究奥尔德尼岛领水不同位置的大型（300 MW）潮汐涡轮机阵列的潜在影响。使用了两种方法，首先只观察水动力变化，其次模拟不可侵蚀床层上的沉积物输送。相对于在沙洲附近收集的 ADCP 速度数据验证了基线水动力模型。从沙波迁移推断出真实世界的沙输送速率，并且与根据模型输出计算的沉积物输送残差一致。沉积物模型的输出再现了河岸上真实的形态行为。考虑了 17 个不同的地点；大多数没有导致南岸上空的显着水动力变化；然而，三个阵列位置被挑出，因为如果要进行开发，则需要格外小心。结果提供了优化阵列位置以实现阵列功率最大化和对沙洲影响最小化的双重目标的案例。本文是主题问题“奥尔德尼岛竞赛中潮汐动力学和潮汐能收集的新见解”的一部分。