Hydraulic structures can be a promising place for tidal energy extraction due to the high flow velocities, easy access to the power grid and easy access for maintenance. However, quantification of the impacts of a tidal power plant in a hydraulic structure is not straight forward. In 2015 a pilot plant consisting of an array of five Tocardo tidal turbines was installed in the Eastern Scheldt Storm Surge Barrier in the Netherlands. This pilot was accompanied by monitoring studies to verify that the operation of the plant had no adverse impact on the barrier and its surroundings. This paper presents the assessment of the hydraulic impact of the tidal power plant in the storm surge barrier based on an analysis of water level and current measurements, combined with numerical modeling and followed by an assessment of the environmental impact with emphasis on the effects on the intertidal areas in the estuary. This validation approach by a pilot plant is imperative to understand the interaction between tidal turbines and the hydraulic structure on the local scale. This understanding gives extra credibility to the predictions of the extrapolated large-scale and large array assessments which will always be fully numerical.

Salt water intrusion through the New Sea Lock of IJmuiden, Netherlands requires mitigation to ensure availability of enough fresh water further inland. For this purpose, a salt screen has been proposed for selective withdrawal of salt water from the Noordzeekanaal in the vicinity of the lock complex. Formulas to assess the withdrawal rate of selective withdrawal are based on idealized layouts and conditions. In the case of IJmuiden, the flow surrounding a salt screen has a strong nonuniform character, such that these formulas are not applicable to predict the correct withdrawal rate and the effectiveness of selective withdrawal accurately. In this case physical scale modeling or computational fluid dynamics (CFD) modeling can be applied. This article discusses the limitations of the formulas for a three-dimensional (3D) flow application near the locks of IJmuiden and presents the use of CFD and physical scale model research to assess the flow patterns around the salt screen and the effectiveness of selective withdrawal. The CFD model was validated against the physical scale model and represented the complex flow fields around the salt screen to within acceptable deviations for both steady and transient states. This gives confidence in applying these more advanced modeling tools for the design and positioning of salt screens in confined complex 3D flow areas.