Coastal erosion is the loss or displacement of land along the coast, as well as the long-term removal of silt and rocks, caused by the action of waves, currents, tides, wind-driven water, waterborne ice, and other storm-related impacts. Over a temporal scale of tides, seasons, and other short-term cyclic events, the landward retreat of the shoreline can be measured and characterized. Hydraulic action, abrasion, impact, and corrosion by wind and water, as well as other natural and unnatural forces, can all contribute to coastal erosion.
Coastal erosion on non-rocky coasts produces rock formations in regions where the coastline contains rock layers or fracture zones with different erosion resistance. Softer parts erode considerably more quickly than tougher ones, resulting in landforms like tunnels, bridges, columns, and pillars. The coast usually evens out over time. Rock formations are worn away as sediment erodes from hard places into softer ones. In addition, erosion is widespread in locations with strong winds, loose sand, and soft rocks. A sandblasting effect is created by the blowing of millions of sharp sand grains. This effect aids in the eroding, smoothing, and polishing of rocks. Erosion is defined as the mechanical action of other rock or sand particles grinding and wearing away rock surfaces.
Sea level rise due to climate change, according to the IPCC, will accelerate coastal erosion globally, drastically altering beaches and low-lying coastal areas.
In geography, what is coastal recession?
The loss of coastal lands owing to the net removal of sediments or bedrock from the shoreline is known as coastal erosion (or shoreline retreat). Coastal erosion can have two forms: danger with a quick onset (occurs very quickly, a period of days to weeks)
What factors influence coastal recession?
Land, infrastructure, and property productivity can all suffer economic consequences. Due to the loss of rural productive land, harbour and coastal erosion may have a negative impact on people’s incomes. The value or price of a property can be reduced as a result of erosion on or near it.
What does the term “coastal erosion” mean?
Coastal erosion is the wear and tear of rocks, soils, and/or sands along the coast caused by rising sea levels, intense wave action, and coastal floods. Storms and other natural phenomena produce erosion along all coastlines; the most damaging conditions are those that combine storm surge at high tide with additional effects from big wavesconditions often associated with landfalling tropical storms. With global sea level rise, the scope and severity of the problem is rising, but it varies across the country, so there is no one-size-fits-all answer.
Which of the four types of coastal erosion are there?
Hydraulic action, compression, abrasion, and attrition are the four basic processes by which destructive waves erode. Jeff Hansen of the United States Geological Survey contributed to this image.
In geography, what is lithology?
The physical properties of a rock, such as its resistance to erosion, are referred to as lithology. A coastline’s lithology influences how quickly it erodes. Because hard rocks (such as gabbro) are resistant to weathering and erosion, a granite shoreline (such as Land’s End) will alter slowly. Because soft rocks (such as limestone) are more sensitive to weathering and erosion, a chalk coast (such as in Dorset) will alter swiftly.
If you looked down on a shoreline from above and looked at the geology of the area, you’d notice that the rock types change as you get closer to the coast, and that the various rocks are grouped in bands. The angle these bands make with the coastline determines whether the coastline is concordant or discordant.
Alternating layers of hard and soft rock run parallel to the coast on concordant coasts. The hard rock works as a protective barrier, preventing erosion of the softer rock beneath it. However, if the hard granite is broken, the softer rock beneath it is exposed, and a cove might emerge (e.g., Lulworth Cove).
Alternating layers of hard and soft rock run perpendicular to the coast on a discordant coastline. The soft rock is degraded faster than the hard rock because it is exposed. Along discordant coastlines, differential erosion forms headlands and bays.
What geological variables influence coastal erosion?
The following are the major elements that influence coastlines:
- Conditions such as cold temperatures and heavy rain accelerate weathering and erosion.
What causes the shore to erode?
Abrasion: In the same way that sandpaper grinds down cliff surfaces, bits of rock and sand in waves grind down cliff surfaces. Attrition: Waves slam rocks and stones on the beach against each other, breaking them and smoothing them down. Solution: Acids in seawater dissolve certain forms of rock, such as chalk and limestone.
Is the ocean capable of flooding?
When dry, low-lying terrain is inundated by seawater, coastal flooding occurs. The elevation of floodwater that enters the inland, which is governed by the topography of the coastal region vulnerable to flooding, determines the range of coastal flooding. Modeling of flood damage was limited to local, regional, and national scales. However, as a result of climate change and rising population rates, flood occurrences have become more frequent, prompting a worldwide search for new methodologies that can deal with both geographical and temporal dynamics.
The seawater can flood the land in three ways: direct flooding, barrier overtopping, and barrier breaching.
Coastal flooding is generally a natural occurrence, but human impact on the coastal environment can worsen it. In the coastal zone, water extraction from groundwater reservoirs can cause land subsidence, increasing the danger of flooding. Engineered protective structures along the shore, such as sea walls, change the natural processes of the beach, frequently resulting in erosion on nearby lengths of the coast, increasing the risk of floods. Furthermore, climate change-related sea level rise and extreme weather will increase the intensity and extent of coastal flooding, affecting hundreds of millions of people.
Introduction
Shoreline
Erosion and accretion are natural processes that cause changes in the landscape.
on a variety of time scales They may occur as a result of smaller-scale events.
Storms, regular wave activity, tides, and winds are examples of (short-term) events.
in reaction to long-term (large-scale) phenomena like glaciation
or orogenic cycles that have the potential to drastically alter sea levels
coastal land subsidence is caused by changes in sea level (rise/fall) and tectonic activity.
or the emergence As a result, most coastlines are naturally dynamic, with seasonal changes.
Erosion is a common component of their ecological characteristics. Wind,
Natural forces such as waves and currents easily shift unconsolidated sand.
and coastal soils, leading in frequent shifts in the position of the
the seashore
Excluding
These processes are merely natural evolutionary phenonema, with no impact from human activities. Human activity (land) near the coast
inside river catchments (reclamation, port development, shrimp aquaculture), and
Offshore (river damming and diversion) and watersheds (dredging, sand mining)
Coastal erosion is frequently exacerbated in combination with these natural forces.
several locations, jeopardizing coasts’ ability to reach their potential.
their long-term socioeconomic and ecological roles at an affordable cost
societal price
Development
Within coastal areas, there has been a surge in interest in erosion issues, which has resulted in considerable changes.
attempts to address coastal erosion issues and rebuild coastal capacity to fulfill both short- and long-term needs
human-caused long-term trends, extreme events, and sea level rise
rise. When countermeasures (i.e. hardening) are used, the erosion problem worsens.
or soft structural solutions) used are ineffective, poorly conceived, or both.
erected or maintained, and if the consequences on neighboring coastlines are not thoroughly considered
evaluated. Erosion is frequently addressed on a local or regional level.
instead of system boundaries that match jurisdictional or jurisdictional boundaries
natural occurrences This oddity is primarily due to a lack of understanding of coastal issues.
Coastal systems’ protective functions and processes
A rise of interest in
Coastal protection structures (including enhanced forest cover) and a
The predominance of a combination of hard and soft structures is consistent with
increased understanding of coastal dynamics and natural defenses There
provides proof that coastal
Figure
Coastal 4.1
Sites of erosion have been observed throughout Asian and Indian Ocean countries, as seen in the inset.
how coastal forest clearance, such as mangroves, has increased
the erosional susceptibility of coastlines (base map source from ITDB, 2004)
Coastal erosion: Extent and causes
Erosion along the coast and
Although accretion is a natural process, it has become abnormal.
common in Asia’s coastal zones and other Indian Ocean countries
as a result of a mix of natural causes, population increase, and
uncontrolled economic growth near the shore, in river catchments, and elsewhere
offshore. This form of erosion has been documented in China, Japan, India, and other Asian countries.
Indonesia, Vietnam, Sri Lanka, Thailand, Bangladesh, and Malaysia are the countries involved.
Bilan
According to (1993), the erosion rate in the northern region of China’s Jiangsu Province is severe, reaching up to 85 percent.
Hangzhou Bay has a rate of 40 metres each year.
In Tianjin, the rate is 1656 meters each year.
Even when protective measures such as sea dykes are in place, erosion still occurs.
built. Beach scour has been discovered along sea-dyke-protected coastlines.
Many variables, such as river damming and dredging, contribute to erosion.
diversion, resulting in less silt being sent to the coast and the clearing of
Coastal places are especially vulnerable to the threat because of mangrove forests.
When these two events are combined, typhoon intensification and storm surges result.
Storm surges have increased during the 42-year period between 1949 and 1990.
Tidal levels surpassing one and two metres have occurred 260 and 260 times, respectively, as a result of rising tidal levels.
As a result, the erosion problem is exacerbated by 48 times. The majority of the
Storm waves carried sediment offshore, but only a little amount of it was returned.
Due to the regular storm strength, it is dangerous to travel to the coast during normal conditions.
The quickness with which
Sagar Island’s coast in West Bengal is eroding.
India is the result of a number of interconnected processes, both natural and man-made.
processes that occur on a regular basis (cyclones, waves, and tides that can exceed six feet in height)
m in height) and anthropogenic activities like human settlement and agriculture.
Mangroves and other coastal vegetation are being removed in the name of aquaculture. The deterioration
From 1996 to 1999, a rate of 5.47 square kilometers per year was determined (Gopinath and Seralathan, 2005).
The northeastern, western, and central parts of the country are particularly vulnerable to erosion.
southwestern and southeastern United States
the island’s various faces Malini and Rao are a couple.
Coastal erosion and habitat degradation along the Godavari River were recorded by (2004).
The delta front has shrunk as a result of the construction of dams across the Godavari and its tributaries, which has reduced sediment flow.
ongoing coastal land sinking and supply to the coast
Sri Lanka is a country in Asia.
Coastal erosion has been a problem since 1920. (Swan, 1974; 1984). It has been successful.
Because mangroves are being wiped out by encroachment, the situation is becoming more serious.
(human settlement), chopping of fuelwood, and clearing
Coastal locations are ideal for intensive shrimp farming. The amount of mangrove forest cover was
In 1986, the area was believed to be around 12 000 hectares; by 1996, it had shrunk to 8 687 hectares.
hectares in 1993 and only 6 000 hectares in 2000, according to estimates (Samrayangke, 2003). 30 dollars approximately
Millions of dollars have already been invested on breakwaters and other infrastructure to combat the threat.
Coastal erosion occurs on both the southern and western coasts (UNEP, 2006); nonetheless, coastal erosion occurs on both coasts.
In some coastal areas, erosion is still a problem.
Plate 4.1: Coastal protection structures in Tanjong Benoa and elsewhere
Sanur Bali has been recognized for its efforts to safeguard the island’s valuable tourism infrastructure. Satellite (clockwise)
photos of the breakwater and artificial headland off the coast, as well as groynes and beach nourishment
(Google maps); coconuts for headland and beach nourishment; loc cit waru
limestone in combination with waru trees for revetment protection
(Note the boats’ perilous placement)
Coastal
Erosion and accretion are complex processes that must be studied from all angles.
the angles of sediment movement caused by wind, waves, and tidal currents; beach
human activities near the coast, and dynamics within a sediment/littoral cell
within river catchments and basins, as well as offshore, at both geographical and temporal scales
Scales of time In terms of time scales, the issue of sea-level rise is a major concern.
complex, and it causes a slew of environmental issues. As the water level rises, so does the cost of living.
The wave base deepens as the water depth rises; waves reach the surface.
Because the coast has more energy, it can erode and convey more material.
consisting of sediment As a result, the coast begins to react to the new sea level in order to retain stability.
a state of dynamic equilibrium The processes of coastal erosion are listed in Figure 4.2.
Natural and human forces, as well as accretion, all have a role.
The solution is simple.
physical criteria that must be recognized in order to recognize coastal erosion as a problem
The following are issues in the coastline zone:
The Wind:
Wind is the most powerful force in wave creation when the conditions are appropriate.
On all open ground, silt from the seashore environment may be transported.
coastlines.
Waves:
They are the primary forces that cause sediment erosion and transfer to the sea.
Coastal area They bring energy and a sequence of currents to the coast.
that transport sediment down the beach (longshore drift)
and usual on the beach (cross-shore transport). It is critical to comprehend
the motion of wave shapes and water particles, as well as their interplay
with seabed materials; and how the waves influence whether the beaches are protected or not
erosive or accumulative
Tides:
They have an impact on the morphodynamics of beaches. They are modulators.
Groundwater is driven by wave motion, which controls the amount of energy arriving at the coast.
tidal currents and fluctuation The interaction of groundwater and tides in the Bay of Fundy
The habitat of the coastal forest is critical to understanding why coastal forests exist.
In some areas, clearing causes significant coastal erosion.
Vegetation:
Important for increasing slope stability, sediment consolidation, and water supply.
some protection for the shoreline
Equally
substantial human activities that must be taken into account across a wide range of spatial scales
and the following time scales:
Activities
Building dwellings along the coast, either through land reclamation or within sand dune regions
Because the development of ports and harbors has a long-term influence
coastline erosion; defensive seawalls result in erosion at the end of the day
structures cause beach scouring at the seawall’s toe, shortening the beach
face. This might happen in the short term (less than five years) or the long term (more than five years).
(It’s been more than five years). Groynes and other structures
In most cases, jetties and other structures generate erosion down-drift of the structure within a short period of time.
a time frame (between five and ten years). dune vegetation removal and
Low-energy shorelines will be exposed to increased energy and reduced pollution as a result of mangroves.
Within five to 10 years, the sediment stability will be compromised, resulting in erosion.
Activities
Dam building and river diversion within river catchments/watersheds cause
Coastal erosion is exacerbated by a loss in sediment supply to the coast.
The impacts of dams and river diversion on coastal erosion are not well understood.
simple, but there are mid- to long-term consequences (20 to 100 years) with
geographic sizes ranging from one to one hundred kilometers
Onshore
actions on land and at sea: Sand and coral mining, as well as dredging, may have an impact on coastal areas.
in a variety of ways, including contributing to a sediment deficiency in the
Modifying the water depth in the coastal system, which results in altered wave refraction
as well as longshore drift The consequences of these acts
will become apparent in a short amount of time (one to ten years).
Understanding
the key mechanisms of coastal dynamics and how coasts work both in and out of the ocean
Human time scales (short and long), as well as spatial and temporal time scales
The activities on the seashore, within the river watershed, and offshore are all important.
Because coastal erosion can happen for no apparent reason, it’s critical to manage it. A
quantitative comprehension of spatial and short- and long-term temporal changes
Scales are required for the development of sensible regulatory policies.
development along the coast (NRC, 1990). Table 4.1 summarizes the various options.
Shoreline change is influenced by a variety of natural and human forces.
a combination of temporal scales, resulting in coastal erosion
Table
4.1
Shoreline change may be influenced by natural and human sources.
The coastal type and
The coastal system’s defensive role
Coastlines
The natural border between the land and the sea is made up of this zone. Their
The sort of rocks exposed along the way determines the natural features.
the action of natural processes, the labor of vegetation, and the shoreline
animals. Their origin was formed by the intensity of natural processes either as erosional or erosive activities.
or depositional characteristics The geological make-up of a coastal area
determines the soil’s stability as well as the degree to which rocky components are present.
as well as their dismantling and removal.
Cliff coasts can be a lot of fun.
It’s called a “hard” coast since it’s made of tough materials like granite.
Rocks that are either sedimentary or volcanic in nature. The shoreline on this sort of coast is usually short.
During low tide, the platform is generally exposed. Erosion is a natural occurrence.
due to slope instability, weathering, and wave action, which results in
The shoreline is receding. Extreme waves, as shown in Figure 4.3,
Storm waves and tsunamis will have a reduced erosive effect on the coastline.
signs of tsunami wave height can be seen on cliffs as a result of this sort of shore
Where trees or shrubs on the cliff had been removed, there was a trim line.
This kind of
This type of coast is known as a “semi-hard” coast since it is made up of cohesive rocks.
It’s found along estuary beaches and has virtually vertical banks.
varying in height from one to five metres The degradation rate is relatively slow.
Because it is made out of weaker and less dense materials than the hard coast, it is higher.
substance that is resistant Coastal processes, weathering, and other factors all contribute to erosion.
a reduction in vegetation cover (ARC, 2000). Storms and other extreme events
As shown in Figure 4.4, vegetation cover has a substantial impact on tsunamis.
By reducing wave height, the coast is protected from flooding and inundation.
As a result of the height, intensity, and decelerating tsunami flow speed, erosive forces are present.
The inundation distance is reduced.
This kind of
Fine-grained sedimentary sediments, primarily, characterize the coast.
It’s a “soft” shore since it’s made up of silt and clay from rivers. It
An intertidal zone is characterized by a broad, moderate seaward slope.
Mangrove forest, saltmarshes, and shrubs grow on a mud flat.
There are many additional trees can be found. The majority of erosion is caused by river damming.
By lowering the water table, it reduces sediment supply, reduces vegetation cover (typically mangroves and saltmarshes), and exposes vegetation roots.
Figure 4.5 shows the mud flat that leads to their eventual collapse. When there are storms,
Healthy and dense vegetation, as well as coastal forest and trees, can act as barriers and deterrents.
lessen the height of storm waves while also providing some protection to the area
in front of them Coastal forest and trees may be reduced in the event of a tsunami.
If the forest is dense, wave height and tsunami flow speed can be affected to some extent.
enough space Both extreme events have the potential to create significant erosion and scouring on the beach.
At the river’s mouth and along the coast.
This kind of
The coast is made up of unconsolidated material, mostly sand with a few stones thrown in for good measure.
It’s a gentle coast, with lots of shells. It has a moderate incline to the sea
Beaches with broad fine sand and a gentle slope are known as dissipative beaches.
hills on the backside of the beach/foredunes Its persona
As a result, profiles can vary depending on wave form, intensity, and wind direction.
modified to give the best effective method of dispersing incoming waves
energy. This type of coast exhibits cyclic erosion or short-term fluctuations.
To detect erosion as a concern, accretion and long-term assessment are required.
here. Due to the fact that accretion and dune rebuilding take far longer than erosional processes, the beach does not have enough time to recover.
Before the next erosive occurrence, rebuild. Erosional
A decreased beach face slope and the lack of a nearshore bar, berm, and erosional scarps along the foredune are notable features.
Erosion is a problem when sand dunes lose their ability to hold water.
During the rebuilding process, vegetation cover that traps wind-borne sediment improves the situation.
Slope stability and sand consolidation Storms, for example, are extreme events.
This type of coast can operate as a barrier for the area during storms and tsunamis (Figure 4.6).
beyond the sand dunes The best natural habitats are sand dunes and associated vegetation cover.
Coastal flooding and tsunami inundation protection measures
This kind of
The coast is made up of unconsolidated material, primarily river sand and eroded rock.
Headlands, shattered coral branches (coralline sand), and fringed shells
reefs. It is characterized as a soft coast with offshore reef protection. The
Depending on the ferocity of the surf, the beach slope can range from gentle to severe.
They are being acted on by natural factors (mostly waves). Waru, coconut trees (Hibiscus tiliaceus),
Casuarina catappa, Casuarina catappa, Casuarina cat
Trees such as pandanus, pines, and other seaside woodland trees
are very common in this area. The loss of (1) the protective role causes the majority of erosion.
coral reefs (where they can be found) and other coastal habitats
(1) coastal trees that defend the coast from wave action; and (2) coastal trees that safeguard the coast from erosion.
Strong winds should be avoided. Healthy coral survives extreme occurrences (Figure 4.7).
Reefs and trees help to safeguard coastlines by limiting wave height and reducing erosion.
As well as significant coastline erosion, energy is a concern.
Coastal regions
can rebuild with natural protective features
themselves following catastrophic disasters or long-term changes such as rising sea levels.
The coastal system’s defensive features differ (Figure 4.8). The significance of