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What Is Backwash In Geography

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Swash and Backwash

Waves are a significant factor in coastal processes as they allow for the build-up or breakdown of beaches. The intensity of the waves is dependent on the amount of energy it carries. Increased energy in waves allows for significantly higher waves, and allows for more frequent coastal erosion events.

Wave intensity and power is highly dependent on wind and tidal conditions. Wind strength significantly impacts how waves operate within coastal processes. In particular, the friction between the ocean floor and wind creates observable swells. The circular movements within waves require energy to ensure their continuous rotation, for this energy allows waves to progress and move forward until they reach the shoreline.

The different characteristics of constructive and destructive waves help us understand how they are able to collect or deposit sediments such as sand and rock particles. Both of these play an important role in keeping the natural balance of our oceans. However, with the increased onset of hydrometeorological hazards such as storms, typhoons, and tsunamis, the way waves function is significantly altered. Humans and biodiversity experience the threat of losing their habitats because of these occurrences, and increased erosion can become dangerous to coastlines.

What Is The Backwash Effect Geography

Backwash occurs if the adverse effects dominate and the level of economic activity in the peripheral communities declines. This growth in urban areas may lead to a decline in rural population and employment if rural-to-urban flows weaken rural economies.

You may ask, What was the contribution of Myrdal to the theory of development economics?

Gunnar Myrdal, a Swedish Social Democrat Member of Parliament and one of the fathers of the Swedish welfare state of the 1960s, helped draft many social and economic programs. As an economist, Myrdal made early contributions to price theory, incorporating the role of uncertainty and expectations on prices.

What Is Trickle Down:

Trickle Down It takes place because of the better facilities and opportunities offered by the growing region. The principle tenet of the theory is that economic growth flows from the top to the bottom. To aggravate the differences further, a rich area may flood the markets of the poorer areas with cheap products, thereby preventing the latter from developing their industries. The result is an industrially expanding region on the one hand, and stagnating or even declining regions, on the other. Eventually, the increased wealth in the initially developed area would percolate. downwards to the less developed areas. This, Myrdal termed as the spread effect or trickle down from the core as the first time. Regions or countries with similar underlying structures are shown to cumulative causation mechanisms that endogenously differentiate into a rich core and a poor periphery.

Fig: Trickle Down ApproachFig: Trickle Down or Top to BottomFig: Spread and Backwash Effects

There are, three stages of regional differentiation

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Caves Arches Stacks And Stumps

Stages of formation:

  • All landforms including Headlands have naturally occurring weaknesses in them. These tend to be eroded faster than the surrounding rock.
  • These areas can gradually form into caves.
  • As a cave continues to erode it can bore through the Headland creating an Arch.
  • The Roof of the Arch is subjected to constant Weathering and can eventually collapse.
  • The pillar of rock left after the Roof has collapse is called a Stack.
  • The base of the Stack can be eroded and the Stack will eventually crumble leaving behind the lower part, this is called a Stump.;
  • What Are The Types Of Waves On A Coast

    Swash And Backwash

    The two types of waves are destructive waves, and constructive waves. Destructive waves are well named, as they have a weak swash and a strong backwash , so they take away much more sediment from the beach than the amount that they deposit. They can be characterised by steep waves that are close together. Constructive waves, on the other hand, are the opposite. They have a stronger swash than backwash, so they deposit more material on the beach than they take away. Constructive waves can be characterised by low waves which are further apart. Think of destructive waves as ‘destroying’ the beach by taking sediment away, and constructive waves as ‘constructing’ the beach, by depositing sediment onto the beach.

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    What Are Swash And Backwash

    Before we move into the meanings of constructive and destructive waves, we first need to understand the push and pull of waves, also referred to as swash and backwash activities. The energy of the swash and backwash help determine the type of wave that occurs.

    Swash refers to when waves travel towards the peach, pushing sediments up the shoreline. This progressive activity allows for the development of beaches and other landforms through a process known as coastal deposition.

    Backwash on the other hand refers to how waves move back down the beach, and back into the oceans. During this process, sediments and other materials on the beach are carried away back into the sea. This process is an important concept in coastal erosion, as backwash aims to return material to the ocean. When waves get stronger, the more likely it is for destructive natural phenomena such as coastal erosion to occur.

    What Is A Beach

    Beaches are wave-deposited accumulations of sediment located at the shoreline. They require a base to reside on, usually the bedrock geology, waves to shape them, sediment to form them, and most are also affected by tides. The beach extends from wave base where waves begin to feel bottom and shoal, across the nearshore zone, though the surf zone to the upper limit of wave swash . In the coastal zone ocean waves are transformed by shoaling, breaking, and swash. In doing so they interact with the seabed, and determine the beach morphology or shape, a process called beach morphodynamics.

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    Are Waves Influenced By Climate Change

    Global warming and changing weather patterns greatly affect how waves function. For example, in the case of an earthquake, tsunamis can sometimes occur. These powerful waves become destructive and easily destroy a shoreline because of the damaging effects of erosion. For these specific reasons, scientists continue to study the earths changing climate condition in order to formulate plans and steps that will help mitigate the damaging effects of these waves.

    References;;

  • Fourie Jean-Pierre et al., 2015, The influence of wave action on coastal erosion along Monwabisi Beach, Cape Town, South African Journal of Geomathics, Vol. 4 , pp. 1 14
  • What Is Cumulative Causation:

    Backwash. The Geographers Dictionary.

    Cumulative causation refers to a self-reinforcing process during Which an impulse to a system triggers further changes in the same direction as the original impulse, thus taking the system further away from its initial position in virtuous or vicious circles of change that may result in a continuing increase in advantages and disadvantages.

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    What Are Destructive Waves

    Destructive waves, in contrast to its counterpart, help erode and remove sediments such as sand and rock particles from the coastlines. These waves are characterized by a strong backwash and a weak swash. The dominating backwash is what helps remove material from the coastline, bringing them back into the sea. These waves are characterized by their tall features in proportion to their lengths.

    These waves are created in aggressive weather conditions such as storms and typhoons where high energy is transferred into these waves. Destructive waves are thus more common in winter than in summer, and usually occur in exposed bays. Because of changing weather patterns and climate change, destructive waves have become more apparent in coastlines, which poses a threat to the landscape and biodiversity that is present here.

    Destructive waves have short wavelengths and high frequencies since around ten to fourteen waves can occur every minute. Because of the presence of a breaker, these waves will eventually plunge towards beaches after reaching a certain height. Because of this, destructive waves do not usually travel far up the shorelines. Furthermore, the high frequency allows for the erosion of materials and sediments back into the ocean since there is usually more water to transport these materials out to sea.

    What Is Back Wash Effect

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    People Also Asked, What is meant by backwash effect?

    In a broad sense backwash effects are the negative impacts of the growth of the core region on the peripheral regions, which tend to be poorer. An example would be the brain drain from many of the poorer parts of Mexico to the large cities, which are seen to be profitable and offer better quality of life.

    Also know, what is the spread effect? The spread effect is the effect that a change in the spread between rates on RSAs and RSLs has on net interest income as interest rates change. The spread effect is such that, regardless of the direction of the change in interest rates, a positive relation exists between changes in the spread and changes in NII.

    Contents

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    Tides And Tidal Currents

    Tides are produced by the gravitational pull of the Moon and Sun acting on a rotating Earth. This pull produces a very slight bulge in the ocean, which we know as tide. The tides and the currents they generate are responsible for about 50% of the marine energy delivered to the coast. The major impact of tides is to shift the shoreline between high and low tide, and to generate tidal currents either parallel to the coast, or at tidal inlets and estuaries, currents flowing into the inlets and perpendicular to the coast .

    Waves Generation And Types

    Transportation And Deposition

    Waves provide about half the energy to do work at the coast. Ocean waves are generated by wind blowing over the ocean surface. The stronger the wind, the longer it blows and the longer the fetch, or stretch of ocean over which it blows, the larger the waves . The world’s greatest wave factories are in the zone of sub-polar lows centered on 4060° N and S latitudes, the so-called roaring 40’s and screaming 60’s. The strong westerly winds produce the world’s biggest waves which initially head west, and are deflected equatorward by the Coriolis effect, arriving from the northwest in the northern hemisphere and southwest in the southern hemisphere . Other major wave climates are the easterly waves produced by the expansive but moderate velocity northeast and southeast Trade winds and lesser seasonal waves produced by the monsoons and even the polar easterlies, together with occasional hurricanes that can produce massive waves as well as storm surges.

    When waves are being generated they are called a sea and consist of short, steep, high, slower waves, which tend to topple over and break, and have a broad spectrum of direction. Once the wind stops blowing, and/or the waves leave the area of generation, they quickly transform into swell lower, longer, faster and uniform in direction. Swell waves can theoretically travel around the world with minimal loss of energy, while in reality they eventually break on some distant shore.

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    Historic Maps And Photographs

    Old Ordnance Survey maps from across England, Wales and Scotland can be browsed at the National Library of Scotland archive

    Use the option Side by Side to compare historic maps with present-day maps and aerial photographs. Below shows an example of how the large scale maps showing field boundaries could be used as a source of data on how much land has been eroded around the East Yorkshire village of Great Cowden since the early 20th century. Much of the village shown in the 1908 map is no longer in existence in the present-day aerial photo .

    Historic maps can also be overlaid over present-day views. The example below shows a 1905 map overlaid over a recent aerial view. The loss of land, roads and buildings on the eastern side of the view is clear. Historic erosion rates could be measured from these views.

    What Is The Role Of Frequency In Waves

    Frequency helps determine the coastal processes that occur in shorelines. Destructive waves generally contain a higher frequency, and with more waves that occur per minute, erosion is usually the end-product. Constructive waves, on the other hand, have lower frequencies, and this allows for a more gentle approach that helps deposit materials.

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    What Are Constructive Waves

    Constructive waves help build and develop coastal areas. These waves are characterized by a strong swash and a weak backwash, and the dominating presence of the swash is what brings and deposits sediments on to these coastlines, thus forming depositional landforms such as spits, tombolos, and bars. These waves are characterized by low heights in proportion to their lengths, and have relatively low energies.

    These waves usually predominante in calm weather conditions when less energy is transferred to the water. Thus, these waves are more common in summer than in the winter. Additionally, these waves typically occur in sheltered bays and spits, where they help build-up and develop depositional landforms along the coastlines

    Constructive waves have long wavelengths and low frequencies, since only about eight to ten waves occur per minute. This low frequency is what helps prevent intensive erosion from taking place, since it hinders the removal of sediments from the coastlines. Because constructive waves lack a breaker component, these waves can simply move up beaches and deposit material at the beachfront. The weak backwash and suppressed wave gradients prevent any sediments from being carried back into the sea after deposition.

    Longshore Drift: Direction And Strength

    What causes Long Shore Drift (Littoral Drift ) – annotated diagram and explanation

    Select 30-50 pebbles of different shapes and sizes from the beach. Use waterproof paint to mark each pebble. Spread the pebbles out in the swash zone, and place a marker further up the beach to show the start point for the pebbles. After 20 minutes find as many pebbles as you can, and measure how far each has moved from the start point.

    After 20 minutes, you may find that some of the pebbles will have disappeared from the beach or moved in a different direction to the others. This does not mean that your results are wrong. Record what happened to each pebble .

    Repeat the experiment at least 3 times, or until you judge that the running mean for distance travelled by a pebble indicates that you have taken an adequate sample.

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    Examples Of Backwash In A Sentence

    backwashbackwash BostonGlobe.combackwash New York Timesbackwash BostonGlobe.combackwash Dallas Newsbackwash The New Yorkerbackwash ProPublicabackwash Scientific Americanbackwash New York Times

    These example sentences are selected automatically from various online news sources to reflect current usage of the word ‘backwash.’ Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

    Explanation Of Cumulative Causation Theory:

    Fig: Graphically presentation of Cumulative Causation

    In the diagram, we have taken two regions of the economy Region A and Region B. We assume that initially, both regions were at the same level of development. To show that, we assume that per capita income is equal in both regions, or that productivity or wage rates are equal in both regions for the same livelihood. Now, I think, this balance is upset as a result of any internal or external inspiration.

    Region A is now progressing faster than Region B. According to Myrdal, this imbalance will remain-there be no re-equilibrium or the two regions will not reach the level of equal development. Rather, economic and social power will work in such a way that region A will continue to prosper by exploiting region B and region B will continue to be depleted. As a result, the difference in the level of development of both regions will continue to increase.

    Video credit by: Examrace

    Myrdal stated 3 main concepts for the basis of this theory.

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    Backwash Effect & Spread Effect

    It is an economic development effect suggested by Swedish economist Gunnar Myrdal.

    It basically means that if one particular area in a country starts growing or developing, it causes people, human capital as well as physical capital from other parts of the country to gravitate towards this growing centre.

    This essentially leaves the other areas worse off than before because their best brains and capital leave them to go to the growing centre. It means that growth in one area adversely affects the growth in the other.For instance, in India, lets say

    • Delhi is the developing centre with all the companies being set up there.
    • Then people from all over Haryana, Punjab, UP, Bihar etc. have a tendency to move to Delhi because all companies are located there and better employment opportunities exist.
    • So Delhi will grow but the remaining areas will be worse off. This is Backwash effect.

    Counter to the Backwash Effect is the spread effect

    • It is an economic development effect suggested by Swedish economist Gunnar Myrdal
    • development in one place, spreads to its suburbs and all the adjoining areas.
    • Again taking the example of Delhi, we could argue that suburbs like Faridabad, Gurgaon, Ghaziabad etc. have benefited from Delhis growth due to the Spread Effect caused by Delhis growth

    Beach Sediment Types & Sources

    1.2 Coasts & Management

    All beaches consist of sediment, which can range in size from sand up to cobbles and boulders. The finer sand result in very low gradient beaches while cobbles may be stacked as steep as 20° . Most beaches with fine to medium sand have a swash zone gradient between 18°.

    In the mid latitudes most beaches are composed of siliceous or quartz sand grains derived from erosion. In the topics, coral reef detritus and shells known as ‘carbonate sediment’ tend to dominate, , while in higher latitudes physical weathering produces coarse rock fragments and gravel.

    Fragum erugatum

    Sediments may therefore be derived from the land and delivered via rivers, glaciers and shoreline erosion, and from marine organisms in the sea. Once at the shore they are moved onshore by wave, tide, and wind driven currents to form beaches. A positive sediment supply produces beach accretion while when negative beaches erode .

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