During the flood tide the sluice gates and turbines are kept closed until a substantial
hydrostatic head has developed across the barrage. Once the sufficient hydrostatic head is achieved, the
turbine gates are opened allowing the water to flow through them into the basin. Flood generation is a
less favourable method of generating electricity due to effects on shipping and the environment. These
effects on shipping and the environment are caused by the average decrease in sea level within the
basin.