To obtain the environmental permit for their annual maintenance dredging the Port of Esbjerg has requested DHI to perform an assessment of the impact on the environment. The port is located in the northern part of the Wadden Sea which is characterized by large inter tidal areas and natural ebb and flood channels. It has a surface area of approximately 135 km2 and a tidal volume of 160×106 m3. The sediment concentration of fines is 0.02–0.1 kg / m3. The material from the maintenance dredging is disposed at two locations and the dredged volumes amount to approximately 90 000 tonnes per year.
Turbidity concentrations near disposal site (red: modelled; blue: measured)
The adopted sediment transport model was thoroughly calibrated and validated before being applied to assess the transport paths and final deposition of the disposed sediments. The model study revealed that the disposed sediment would remain within the tidal area. The impact of disposal of off-shore disposal indicated that only a small percentage of the disposed sediment would return to the tidal area. In the long term this could potentially lead to a reduced sedimentation rate at inter tidal mud flats.