Harbours are natural or artificial places along the coast line used to provide protection and anchorage for ships and small boats. The construction of harbours is a challenge for civil engineers because ocean wave climates are difficult to predict. Waves have the ability to find the weaknesses in a structure.
Sometimes natural harbours are found along the coastlines which require a minimum of improvement. Usually these natural occurring harbours determined where major coastal cities were built. Vancouver Harbour is considered a natural harbour because the ships are sheltered from ocean waves by the surrounding land and nearby islands.
Port Québec is also considered to be a natural harbour.
Unfortunately natural harbours are not always available where people wish to build ports and artificial harbours have to be constructed. Locations of these artificial harbours are usually chosen where there was an indent in the coastline. Sometimes it is necessary to build harbours on unprotected pieces of coastline. In these cases the harbour is almost entirely closed in by breakwaters with small openings to allow the passage of ships.
The Cardiff barrage is an S-shaped tidal dam consisting of an embankment, breakwater, sluices, locks, and a complicated fish pass. Together they form an enclosed harbour shelter turning the tidal mudflats into a freshwater lake. The breakwater is built to allow waves to enter and to dissipate energy. To meet environmental requirements, new seabird feeding ground habitats were built to compenstate for those lost to the lake.
The idea of a harbour is to assist in transferring goods or people from the ship to land or to another form of transportation. Civil engineers must ensure that there are large areas of dry land immediately beside the ship's berth. This land must be firm and be able to support the load it is expected to carry. Gravity retaining walls which extend deep into the seabed are commonly used to keep the land in place. Engineers must first examine the soil conditions before designing and constructing the wall to determine how deep the wall must go. Originally the walls were made of rock but now are usually constructed of either plain or reinforced concrete.
Scale models of the harbour and surrounding areas are built and then subjected to the same tides and streams that the finished harbour will have to endure. Thus the effects of many years of tide action can be studied in a few weeks. The models can even help detect areas where there would be a tendency for the sea to remove or leave behind silt. Using wave generating devices, the positioning of the necessary breakwaters can be studied.
Sometimes the harbour isn't deep enough to accommodate some of the extremely large ships so artificial docks must be placed in the deep water.