The fulfillment of appropriate similarity criteria is a necessary condition for the physical model to provide a reliable reproduction of the reality. Therefore, large facilities are typically needed to apply physical models of large harbors. However, their scale cannot be too small, as the effect of viscosity may prevail over turbulence if the prototype is compressed to a small size. They present the relevant advantage of allowing repeatable experiments and allow to reproduce highly heterogeneous, turbulent and 3-dimensional processes. Physical models and laboratory experiments are frequently used to model sediment dynamics in coastal areas. Planning and managing dredging activities are essential tasks to port operation and maintenance, that are regulated by prescriptions and technical guidelines issued by national and local administrations and port authorities. ![]() Dredging may be carried out by using a set of techniques that are characterised by different operational modes and impact on the port activity and the environment in general. The material resulting from dredging may be used for beach replenishment or other forms of recycling. Dredging is the removal of sediments and mud from the bottom of water bodies. To maintain the functionality of ports in the presence of significant siltation it is often necessary to perform harbor clearance works through dredging. Contamination may be due to local or non-local sources. An issue related to harbour siltation is the degree of contamination of the deposited sediments and mud, which is impacting the dredging procedures and costs. Harbour siltation is higher (factors up to the value of 5 have been observed) in salt and brackish water conditions than in fresh water conditions (van Rijn, 2016), for the higher concentration of sediment and the generation of stratified flow in the presence of salt water. density difference inside and outside the basin.peak tidal current outside the entrance. ![]() To give an example, volumes of sediments up to 3.5 millions of cubic meters per year (with a tickness up to more than one meter) have been observed in the Botlek New Waterway, in Rotterdam. Siltation rates vary depending on the characteristics of the harbour and the marine environment. Dynamics of sediments in low energy environment Siltation reduces the sea depth and may originate obstruction of the port traffic (see Figure 1).įigure 1. In fact, siltation is often experienced when a low energy environment is located in the proximity of a high energy one that has the capability to mobilise the sediments themselves. A side effect that often arises is the deposition of sediments due to lowering the energy of the marine environment inside the harbor with respect to the immediate outside. Harbor basins and ports are often protected with structures like breakwaters to mitigate the impact of waves and currents therefore creating a sheltered environment to facilitate the approach of ships and mooring operations.
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