It is widely known that climate change will cause sea level rise and larger river discharges in the close future (because more precipitation during a shorter amount of time will happen). In the Netherlands, the delta works were developed to protect the hinterland from sea-water during storm surge situations. The storm surge barriers close and the water is kept at the sea. However, if large river discharges are present together with storm surge, the water level behind the barriers will rise because the closed barrier won't let the river water out. In delta areas, this is a major threat to water safety. To tackle these future problems Huub Lavooij and Leen Berke came up with the DELTA21 plan.  The plan is to build a storm surge barrier together with pumps that can evacuate the water from the river in the event of having both storm surge and large river discharges happening simultaneously. As this situation will happen once every ten years on average, there is a risk that the pumps might not function when needed if they were on hold for ten years. To tackle that problem and also producing green energy, a hydro pump storage basin is proposed to take advantage of the pumps already installed for flood protection. This hydro pump storage basin is called Valmeer. As this structure would be built next to the Maasvlakte 2, in a red Natura 2000 area, some ecological value must be gained with this project in return. That is why the Getijmeer (tidal lake) was created. This tidal lake would allow opening the Haringvliet sluices and thus recovering fish migration in that area. Bringing then the ecological, recreational and economic value to the Haringvliet area, which is currently closed to the sea. The objective of this thesis is to create a conceptual design of a hydro pump storage station able to turbine water in for energy generation and to pump it out for the same purpose and also for water safety.  For designing the plant, three locations and three different alternatives were considered. Finally, a pump storage station that is also a storm surge barrier is proposed in the northern part of the DELTA21 plan, next to the Maasvlakte 2. Aspects such as constructability, affection of sediment transport to the plant, wave loading and access to the plant were taken into account for choosing the location and the most suitable alternative.  The chosen alternative was found to be a good option if special care is taken about piping protection (the structure is subjected to head differences of 23 meters) and about methods to avoid water infiltration into the building pit during the construction of the plant (the building pit's floor is at NAP -32 m).  As a part of the design, a life cycle analysis on CO2 emissions was performed. This showed that the hydro pump storage station can bring positive ecological value in terms of CO2 emissions reduction for the grid of the Netherlands. Producing energy at 280 g of CO2/kWh at present grid conditions and at -140 g of CO2/kWh if renewable energy is used to power the pumps. The conventional fossil fuel energy-producing methods do it at between 500 and 1050 g of CO2/kWh.  Therefore this thesis shows that the DELTA21 plan is not only good for flood protection but for renewable energy generation. Contributing then to the United Nations Sustainable Development Goals of "affordable and clean energy" (energy generation function) and "life on land" (water safety function).