Training (civil)
Encyclopedia
Training or entrance training refers to coastal structures
built to constrain a river discharging across a littoral
coast so that it discharges only where desired. Untrained entrances on sandy coasts tend to move widely and violently to discharge into the ocean, often upsetting those enjoying land nearby. With many cities (and buildings) constructed close to rivers, such management has historically been considered a necessary course of action, even though ecologically, non-intervention would be better and more sustainable.
A trained entrance often consists of rock walls that force the water into a deeper more stable channel
. Trained entrances can provide better navigation, water quality and flood
mitigation services, but can also cause beach erosion due to their interruption of longshore drift
. One solution is the installation of a sand bypass system across the trained entrance.
Training is also used on mountainous rivers and streams, and ensures that a fast-flowing river is reduced in violence (and hence erosive
capability), usually by the use of weir
s and other structures like gabion
s.
Coastal management
In some jurisdictions the terms sea defense and coastal protection are used to mean, respectively, defense against flooding and erosion...
built to constrain a river discharging across a littoral
Littoral
The littoral zone is that part of a sea, lake or river that is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. It always includes this intertidal zone and is often used to...
coast so that it discharges only where desired. Untrained entrances on sandy coasts tend to move widely and violently to discharge into the ocean, often upsetting those enjoying land nearby. With many cities (and buildings) constructed close to rivers, such management has historically been considered a necessary course of action, even though ecologically, non-intervention would be better and more sustainable.
A trained entrance often consists of rock walls that force the water into a deeper more stable channel
Channel (geography)
In physical geography, a channel is the physical confine of a river, slough or ocean strait consisting of a bed and banks.A channel is also the natural or human-made deeper course through a reef, sand bar, bay, or any shallow body of water...
. Trained entrances can provide better navigation, water quality and flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
mitigation services, but can also cause beach erosion due to their interruption of longshore drift
Longshore drift
Longshore drift consists of the transportation of sediments along a coast at an angle to the shoreline, which is dependent on prevailing wind direction, swash and backwash. This process occurs in the littoral zone, and in or within close proximity to the surf zone...
. One solution is the installation of a sand bypass system across the trained entrance.
Training is also used on mountainous rivers and streams, and ensures that a fast-flowing river is reduced in violence (and hence erosive
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
capability), usually by the use of weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...
s and other structures like gabion
Gabion
Gabions are cages, cylinders, or boxes filled with soil or sand that are used in civil engineering, road building, and military applications. For erosion control caged riprap is used. For dams or foundation construction, cylindrical metal structures are used...
s.