![]() ![]() In fact, there is an individual type of sediment management for every ratio. In an estuary the ratio between what is transported away by the river and the tidal volume is important. This applies to dykes, polders and dredging itself. In many places in the world this process is accelerated by human activity. This is because the river flowing into it transports sediments to the estuary, while a great deal of sediment also comes in from the sea. Naturally, estuaries tend to silt up rather than become eroded. Maintenance dredging in estuaries (an estuary is a semi-enclosed coastal body of water which has a free connection with the open sea and within which sea water is measurably diluted with fresh water derived from land drainage – Pritchard, 1967) is a continuing and unrelenting expense. Maintenance dredging is concerned with maintaining the depth of the channel. Capital dredging for navigation purposes is the excavation of sediments to increase depths in an area to accommodate the draft of vessels. It is important to make a distinction between maintenance dredging and capital dredging. ![]() By way of example, I would specifically like to look at the case of Antwerp. For example, it might be more profitable for a region to move the port itself, although this is rather unlikely, in view of the enormous costs of port infrastructure. In this respect it is necessary to consider whether the social benefits of increasing the size of the fairway, or even merely the maintenance dredging, are higher than the costs incurred by this. ![]() For the access to most ports dredging has become a fundamental activity. Globalisation, trends in logistics, scale increases in vessel size and a new port hierarchy in the European port system mean that it is necessary to enlarge the fairway to these ports so that they can continue to play a role as motors of economic prosperity. The issues which ports are facing at the moment are multiple and complex. ![]() Access to these ports was not a problem for the types of ships which were present at the time. Most ports were built in locations which naturally provided the necessary maritime access. ![]()
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