What is morphology?
Morphology is the study of the interaction between the movement of the water, the movement of sand and silt in the sea, and the erosion, accretion and silting that occur along the Dutch coast and in the North Sea.

The North Sea is a dynamic system. Both the water and the seabed are in constant motion. This water movement is a complex combination of tide, wind, waves and the inflow of fresh river water at the river estuaries. Under the influence of the water, the bed of the North Sea also changes. This consists mainly of sand and to a much lesser extent silt. The constant wave action churns the sand and silt away from the bed. Currents then cause the sand and silt to move. This material will settle again later when conditions are quiet and in sheltered areas.

Silt movements are mainly concentrated in a strip of between about ten to twenty kilometres wide along the coast. The major sand movements occur in the surf zone, which is the shallow foreshore where waves break on the coast. In deep water, sand movement only occurs under the influence of tidal flow. Sand movement in deep water occurs only under the influence of tidal flow. Sand movement at sea and the silt movements are circulatory and travel in a northerly direction. The direction of the sand movement in the surf zone depends on the orientation of the coast relative to the incident waves. As a result of the sand movement in the surf zone the coastline and the shallow foreshore are constantly changing. The coast can both erode and accrete.

Influence of Maasvlakte 2 on the morphology
The construction of Maasvlakte 2 will influence the morphological processes. The land reclamation will create a physical barrier for waves and for the tidal flow along the coast. This will affect the movement of sand and silt in the sea. In the long term, this process could change the position of the seabed.

• Possible consequences of Maasvlakte 2 are:
  Either more or less maintenance dredging in the waterways from and to the port of Rotterdam (the Euro-Maasgeul and the Maas estuary). An accurate forecast of the future scale of this maintenance dredging is important in connection with the related costs.
• Changes in the coastal maintenance requirements in the area just to the north and to the south of Maasvlakte 2 (the coast of Delfland, Voorne and Goeree).
• A changing structure of the surface inter-tidal zone with channels, mudflats, sand flats and shallows to the south of Maasvlakte 2 (the Haringvliet estuary), with possible consequences for the nature present in this area. Should the position of the Haringvliet estuary bed change, there will also be local consequences for the waves. This, in turn, can lead to a reduction in salt spray on the dune coast of Voorne and Goeree. This could in turn have an impact on the nature present in this area.
  Prior to the construction of Maasvlakte 2 a thorough insight is necessary into the exact morphological effects of the land reclamation. This requires a great deal of research. Only then is a correct assessment possible in the plans.

The Maasvlakte 2 seawall
The more seaward position of the Maasvlakte 2 coastline will expose it to heavier wave and current action than the existing Maasvlakte. It is important to take this fact into account when designing the seawall for protection of the reclaimed land against the sea. Maasvlakte 2 will have a predominantly soft seawall. Just as almost everywhere else on the Dutch coast, this seawall will consist of dunes behind a beach. The sand concerned will not stay in place of its own accord. Waves and currents erode the beach. Where this happens, the sand will need to be replenished from time to time. This method has been applied everywhere along the Dutch coast since 1990. The frequency and quantities which will be involved in the Maasvlakte 2 sand replenishments are the subject of extensive study. The conclusions will be of great importance in budgeting the maintenance costs of the seawall.

The expected erosion of the Maasvlakte 2 beach will be influenced by many factors. The ultimate shape and position of the soft seawall will play a role, as will the type of sand to be used in the construction of the seawall and for replenishment. The smaller the sand grain, the easier it will be for the sand to be carried away. Therefore, the larger the grain size, the less maintenance will be required. For this reason the soft seawall will consist of relatively coarse sand.

Erosion pit
Along the west coast of Maasvlakte 2, a significant erosion of the seabed is expected due to the increasing tidal flow. This will cause the formation of a so-called erosion pit. With the construction of the harbour dams in IJmuiden a similar thing also occurred. In theory erosion pits can become dozens of metres deep. The current depth in this location is between fifteen and twenty meters.
Whether and to what extent an erosion pit will be created must be determined by study. Should the erosion pit become deeper than twenty meters, it has been agreed that extra compensation will be necessary in the marine reserve to be constructed to the south of Maasvlakte 2. It might be possible to limit the formation of an erosion pit by taking supplementary measures such as local protection of the seabed by means of a rubble layer.

Silt movement
The construction of Maasvlakte 2 will also influence the large-scale movement of silt in the North Sea. In order to make an accurate forecast of the ecological impact of this on the Dutch costal zone, it is important to thoroughly survey these changes in the silt movements. The impact will not only be on the area around the future reclaimed land, but also on the coast near Voorne, Goeree, Delfland and further to the north. Earlier studies have revealed that Maasvlakte 2 and the associated sand winning could have an influence on the North Sea environment as far as the entrance to the Wadden Sea. Confident predictions of the precise impact are impossible with the scientific means currently available. However, the Council of State has determined that greater clarity is needed on this issue. Therefore, within the framework of the recovery of the PKB-plus, fundamental research will take place into the impact of Maasvlakte 2 on large-scale silt movement in the North Sea. The client is the Rotterdam Mainport Development Project (PMR) Organization.

Part of the silt movement along the Dutch coast flows into the port entrance at high tide and then into the harbour basins where it subsequently settles. In order to maintain the depth of the of the port at the right level some eight million m³ of silt per year currently have to be dredged in the Maas estuary. Current research has shown that the construction of Maasvlakte 2 will lead to less silting of the Maas estuary and the port basins, and therefore to less maintenance. Due to the land reclamation the flow pattern of the port will change. As a result, the silt concentrations immediately outside the port entrance will reduce, particularly during high tide.

Sand winning
The construction of Maasvlakte 2 will require several hundred million m³ of sea sand. A separate investigation is concentrating on the possible impact of this sand winning on life in the North Sea. If the sand is won with trailing hopper dredgers, a small proportion of the silt will escape, and will then be spread by the current in the surroundings of the sand winning sites. From an ecological point of view, it is important to know what kind of silt concentrations are involved because of transparency and turbidity, and where the silt will ultimately settle thus covering the seabed life.

The sand winning pits will also disturb the seabed for a considerable time to come. The best design of sand winning pit (i.e. position, depth and dimensions) will therefore be investigated from an ecological point of view.

The current studies will form the basis for the ultimate selection of the sand winning sites, for the design of the sand winning pits and for the taking of any measures, such as environmentally safe dredging, which will limit as far as possible the unfavourable impact on the sea and coastal environment.

Advanced computer models
From the first design exercises for Maasvlakte 2, many prominent institutions and consultancies have worked on the development and validation of an extensive set of models for answering morphological questions. The techniques, software and hardware applied have evolved greatly in the course of the past seven years. As a result, it is now possible to make realistic forecasts of the morphological developments for a relatively long period. The Netherlands has a worldwide lead in the modelling of morphology and silt movement. The new investigation that is currently in progress into the silt movements at sea, within the framework of the recovery of the PKB-plus, is an additional advance for the discipline. This investigation is also of great importance with a view to any more detailed calculations in the future.

State of affairs
The investigations into the morphological impact of Maasvlakte 2 are part of the current environmental impact assessment (EIA) for the land reclamation. Further decision-making will take place following completion of the EIA.