The combination of continuous sea level rise, and more frequent extreme river discharges will become a rapidly developing problem for the Rhine-Meuse delta over the course of the next century. The current Dutch delta management policy mostly revolves around the consistent improvement of the existing dikes to account for the increasing water levels in the region. An alternative solution to this problem is the Delta21 project. The Delta21 project proposes the construction of a large scale storage lake, and a high capacity pumping station at the Dutch coast. The project is meant to allow for the simultaneous closure of the storm-surge barriers on the Dutch coast, while actively discharging river water that would normally be pilling up behind the closed barriers. The Delta21 project foresees it will be able to save up to 5billion euros by the end of the century in dike reinforcement costs. In order to enable the flood safety operation of the Delta21 project, the project also requires the construction of a new storm-surge barrier in the Haringvliet ebb-tidal delta, roughly 10km away from the current Haringvlietsluices. The objective of this thesis is the conceptual design of the new Delta21 storm surge barrier, the New Haringvliet barrier. The aim of this design process is to identify critical design components, and requirements that could potentially be hurdles in the development of the New Haringvliet barrier, as well as the overall Delta21 project. For the hydrodynamic design of the barrier, a schematized 1D hydrodynamic model was used to get a first insight into the impact the new barrier will have on the on the tidal range in the tidal delta. As well as how much it could potentially impact the reintroduction of the tide to the Haringvliet. The reopening of the Haringvliet would be a part of Delta21's effort to restore some of the local ecological value to the region as a compensation measure for the project. Additionally, the model was also used to determine the effects of the construction of the barrier on the capability for the system to handle high river discharge rates. The findings of the assessment show that the selection of a small tidal opening in the New Haringvliet barrier will significantly negatively impact the capability for the system to discharge high river water, as well as limit the amount of tidal range that will be available in the system. It was determined that constructing the barrier with a tidal opening with an effective cross-section of 10000m2 will provide the best balance between hydrodynamic performance of the system, and barrier construction costs. An analysis of the possible Delta21 construction sequences was used to determine the preferred construction method for the barrier. In this analysis, an economic construction sequence alternative, and an environmental construction sequence alternative were developed, and consecutively evaluated using a multi-criteria analysis. This MCA revealed that the construction of the New Haringvliet barrier using prefab construction elements and techniques was the desired construction method for the project. The results of hydrodynamic and construction sequence assessment, were used as the basis for the barrier's spatial design. The structure was designed with a total of 20 vertical lift gates, each spanning 80m. This would bring the total tidal opening to 10400m2. Vertical lift gates were chosen for the design due to their great reliability and overall cost effectiveness, which are both important considerations for a barrier of this magnitude. On the southern side of the barrier a shipping lock will be the barrier's primary navigational opening. The final phase of the conceptual design focuses on the design of the gated barrier section, and includes the validation of the transport stability of the caisson, the design of the vertical lift gates, and the design of the scour protection and it's filter layers.