The port of Schülperneuensiel is located in the dike foreland on the south bank of the Eider. Around 1600, Neuensiel was relocated to the new sea dike. When the Karolinen- and Wesselburenerkooges were re-covered, Neuensiel remained. Today's drainage sluice was built in 1964/65. This is a peak pumping station with a dyke.
Normally, the dyke is used for drainage, but the pumping station is switched on when the Eider reaches peak water levels. Three pumps can pump a total of 11,400 liters per second into the Eider. The sluice associations Wesselburenerkoog, Karolinenkoog, Schülperweide, Hillgroven, Schülp, Strübbel and Neuenkirchen drain an area of 6,321 hectares here. Inside the pumping station is a five to six hectare reservoir. 75,000 cubic meters of water can be absorbed here.
There used to be a lot of shipping traffic in the port. The main commodity was grain. Today the port area is leased to sailors. The Eider foreland and the tidal flats are part of a salt and brackish water area of the Eider estuary that was designated as a nature reserve in 1989 and is influenced by the tides. The characteristic plant and animal species that occur are protected on around 620 hectares. Despite the change in the tidal rhythm, the associated changes in salinity and the bank vegetation due to the construction of the Eider barrage in 1973, numerous red-listed species have found a refuge here; the Eider estuary is still considered a wetland of international importance.