Coastal Structures

Coastal structures are termed “hard” structures.

These structures are typically constructed from materials (at least for some coasts and beaches) including concrete, large armour stone, steel, or timber, and are spatially repaired within an anyway dynamic coastal zone.

 These materials are generally permanent (typical design exists for 50 years).

In this article you’ll learn:

  • Purpose of the coastal structures.
  • Types of coastal structures.
  • Merits and Demerits of the coastal structures.
  • Lots more.

So, if you’re ready to go with coastal structures, this article is for you.

Let’s dive right in.

What are Coastal Structures?

Coastal structures are buildings built close to coastal areas for a variety of purposes.

Various types of coastal structures are built under various conditions, but the selection and design criteria are used for each type of coastal structure must be legitimate and in accordance with the standards.

A broad range of factors must be considered in the selection and design of coastal structures are as follows:

Sandcastle on a Florida Beach
  1. Criteria for structural stability.
  2. Operational performance standards.
  3. The selection and assessment of coastal structures should focus on these two areas.
  4. Extreme environmental conditions are frequently linked to structural stability criteria because they can seriously harm or even destroy a coastal structure.

Therefore, these stability standards are related to environmental episodic events (such as earthquakes, hurricanes, and strong storms) and are frequently assessed using the risk of encounter probabilities.

Calculating the encounter probability (Ep) as follows is a quick and easy way to assess your chances of experiencing an extreme environmental event:

Ep = {(1-1/1) TR},

where TR is the return period.

L is the structure’s design life.

Coastal Structures

Purpose of Coastal Structures:

The coastal protection structure’s main objective is to shield the coastline from storm surges and other sea-related natural disasters.

 Increased access to the sea from the land is made possible by the coastal protection structure while erosion is decreased.

Erosion is brought on by hydraulic action—the power of the waves themselves.

Types of Coastal Protection Structures:

Coastal Armoring Structures:

Seawalls:

All coastal and shoreline defines structures share a close relationship to the land in terms of both construction and function.

The shallow water that seawalls and dikes typically border also has the corresponding hydraulic loadings.

There are many different types of materials and cross-sections that have been used to build seawalls, the most typical cross-sections for seawalls are as follows:

  • Slope protection (with or without berm).
  • Bund for reclamation.
  • The restoration of a vertical wall mount.
  • Anti-scour mat in front of a vertical wall is already present.

To protect coastal structures and areas from the damaging effects of ocean wave action and flooding caused by storms, seawalls are frequently built and run along the shoreline.

Bulkheads:

Bulkheads can be built out of steel, concrete, or wood. The two main types are based sheet pile walls and gravity constructions.

The bulkheads may not have been subjected to particularly strong wave actions, and their primary function is to hold back earth, but the designer should take scouring at the base of the structure into account.

When rock is close to the surface and sufficient penetration for an anchored bulkhead type cannot be achieved, cellular sheet pile bulkheads are used.

The sheet pile must also be sufficiently reinforced to withstand the bending moment, soil properties, hydrostatic pressures, and support points.

Revetments:

Revetments are frequently constructed as permeable structures using natural stones or concrete blocks, strengthening wave energy absorption and reducing reflection and wave run-up.

They have always been established as sloping structures.

Revetments can also be made of various slabs of concrete, some of them permeable and interlocking. They become stronger and more absorbent thanks to this method.

Revetments can also be made of mattresses, tubes, and geotextile fabric bags filled with sand. To prevent the fabric from deteriorating, such structures need to be UV-protected.

Frequently, sandbagging is employed as an emergency defense.

Geotextile fabric revetments lack a natural appearance and are vulnerable to mechanical impact and vandalism.

Beach or Soil Stabilization Coastal Structures:

Nearshore Breakwater:

Offshore breakwaters are typically shore-parallel constructions that successfully lessen the amount of wave energy that reaches the shoreline that is being protected.

 They can be constructed farther from the shore, in which case they are known as offshore breakwaters, or they can be constructed close to the shoreline they are intended to protect.

Breakwaters reduce wave energy in their lee when used to stabilize beaches because this lowers the waves’ ability to carry sediment.

They can be made to encourage the accumulation of natural sediment to create a new beach or to prevent erosion of an already-existing beach or beach fill.

Groins:

Groins are shore protection coastal structures that alter the offshore current and wave patterns to lessen the effects of erosion on the shoreline.

They are categorized based on their length, height, and permeability and can be constructed from materials like concrete, stone, steel, or wood.

It can be impermeable or permeable and are often built vertical position to the shoreline.

Containment Dikes:

Containment dikes are berm or retaining walls made of concrete, earth, or both that can be temporary or permanent that are used to contain spills in structures.

Diking, one of the most common forms of containment, is an effective method of environment protection for the above-ground liquid storage tanks and the rail car or tank truck loading and unloading regions.

 Diking can offer one of the best safeguards against stormwater contamination because it encloses the problem area, contains the spill, and keeps the spill materials isolated from the stormwater outside of the diked area.

Dikes typically have a mild slope, typically of the magnitude of 1:2 or less. A dike is made up of an inner slope, a crest, an outer slope, which is frequently beamed, and toe construction.

Reef Breakwaters:

Reef breakwaters are long and short submerged coastal structures that run parallel to the coast and are intended to force waves trying to break over the reef to reduce wave action on the beach.

They are usually built as an even mass of stone or concrete armor units that resembles a structure made of rubble.

The breakwater can be made to change shape due to wave action or it can be formed to be steady.

Reef breakwaters can be narrowly crested like disconnected breakwaters in shallow water or wide crested with a lower crest elevation, comparable to most natural reefs that have a fairly wide rim parallel to the coastline.

In addition to breaking waves and subsequent energy dissipation, reef breakwaters could be used to control wave action by refraction and diffraction.

Submerged Sill:

A submerged sill is a particular kind of reef breakwater that is built near the shore and then used to add a structural shield to the beach profile in order to slow the motion of offshore sand.

The onshore sand movement, however, might also be halted by the sill. The sill creates a break in the beach profile, making the beach behind it perched because it is wider and at a higher elevation than nearby beaches.

Additionally, beach material that has been artificially positioned on the beach profile behind the sill is retained using submerged sills.

Typically, submerged sills are constructed using prefabricated or commercially available rock-armored or rubble-mound structures.

Sills that are submerged pose an invisible risk to boats and swimmers.

Navigation Coastal Structures:

Breakwaters:

The arrangement and cross-section of a breakwater have some bearing on the hydraulic loading of the armour or cover layer.

 Furthermore, these geometrical features are what primarily determines the bulk volume of a breakwater. Due to their protruding position, breakwaters are frequently exposed to relatively high wave loadings.

It is frequently necessary to place high demands on the armour components, construction methods, and equipment because the required armour strength strongly depends on the wave height.

Overtopping may be permitted or not depending on the specific function of the breakwater, a decision that has significant implications for the structure’s design.

The most popular breakwater concepts are as follows:

  • Berm breakwater; conventional rubble mound breakwater.
  • Reef-like architecture.
  • a submerged or low-crested breakwater.
  • a rock-based caisson breakwater.
  • Breakwater with a composite caisson and rubble mound.

Jetties:

Typically, materials like concrete, steel, stone, wood, and occasionally asphalt used as a binder are used to construct jetties.

This structure is built at a harbor or river mouth and extends into deeper water to prevent sandbar formation and control currents.

Design of Coastal Structures - Breakwater

Advantages of Coastal Structures:

  1. This is the best for stabilizing a shoreline at a specific location.
  2. It protects against or mitigates flooding.
  3. Coastal structures can have detrimental ecological effects within the coastal zone and partially impede recreational use of the coastal zone.

Disadvantages of Coastal Structures:

  1. It has visual effects.
  2. Access limitations on both the horizontal and vertical axes.
  3. It also has a crushing defeat of sand due to the armouring of the shoreline.
  4. Placement losses due to the construction of a seawall or revetment.
  5. They have passive deterioration.
  6. Also has active erosion.
Also read: Pneumatic Structures | Types of Structures | Diagrid Structural System

Conclusion:

The coastal protection structures were constructed to shield a portion of the shore from beach erosion and seawater flooding.

The configuration of the shoreline can be greatly impacted by coastal structures, while impacts are brought about by the building, upkeep, and structures.

Hello, I'm Rahul Patil founder of Constructionor.com, I had studied B.E. Civil. This blog provides authentic information regarding civil structures, equipment, materials, tests & much more.

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