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29 Cards in this Set
- Front
- Back
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List and describe 6 different soft engineering methods.
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- Beach nourishment (Adding sand from external sources, widening the beach and reducing wave energy to reduce erosion rates) - Beach Stabilisation - Making efforts to stabilize the beach by reducing the slope of the beach as well as adding vegetation and tree trunks to help stabilize the land itself. - Dune Regeneration - This usually occurs as a result of beach nourishment and / or stabilisation. Dunes are particularly useful because they can act as a barrier between the land and the sea, reducing the wave erosional power and ultimately reducing coastal erosion. Dune regeneration can be encouraged by introducing vegetation species such ass glasswort to help colonize and stabilize the dunes. - Land Use Management - This involves the implementation of things like walkways which aim to reduce the amount of 'trampling' and damage to ecosystems and vegetation particularly at dunes, as the vegetation plays a vital part in the stabilization of the dunes. Damaging the dunes through trampling can lead to it being increasingly vulnerable to erosion. - Creating Marshlands through pre-existing mudflats can prove to be effective. By introducing a species of quickly colonizing vegetation, such as the glasswort, marshlands an be created. The vegetation stems and leaves serve to slow down incoming waves, reducing their energy and preventing them from reaching as inland as they used to. This subsequently reduces rates of coastal erosion as well as frequency of coastal flooding. - Coastal realignment this involves the removal or 'breaching' of pre-existing hard-engineering defences to allow the waves to flood inland. The idea is to allow the eventual colonization of vegetation on mudflat areas which will subsequently lead to the formation of marshlands which will, as previously mentioned, allow for the reduction of coastal erosion and flooding through the effective ways of reducing wave energy and velocity that come with the stems and leaves of the vegetation, particularly the glasswort species. |
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Why is soft engineering considered to be a more sustainable approach to coastal management?
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Hard engineering is often very costly, and demands that a lot of time and money be spent to maintain the schemes put in place. Another large issue with hard engineering is that a lot of the produced schemes have a significant negative impact on the natural processes which are taking place in an area.
Soft engineering, on the other hand, works to integrate with natural processes, and in some cases even works to nourish ecosystems through the use of creating marshlands and dunes to facilitate for the colonization of vegetation such as the glasswort. Soft engineering also demands much less money and time be devoted to schemes, as most of the work is done by nature itself. Overall, it is considered to be a much more sustainable option as it impacts the environment much less, and is also less costly to the economy, making it both environmentally and economically sustainable. SUMMARIZE: H.E. (bad): - Expensive and requires a lot of time to both construct and maintain. - Damages natural processes. S.E. (Good): - Much less time and money required for maintenance (nature does most of the work). - Strives to integrate with natural processes, rather than disrupt it - Can nourish ecosystems through dune regeneration and marshland creation. - Overall more sustainable in terms of environment and economy as it is less impactful and cheaper. |
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What is the ultimate aim for coastal management?
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The ultimate aim for coastal management is to help protect businesses, homes and the environment from erosion and flooding.
This is because erosion and flooding can have significant economic, social and environmental impacts. |
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Describe the problems of a named area attempting to cope with the effects of coastal erosion.
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Holderness:
- Implementing groynes have widened beaches and reduced sediment supply further down the coast, causing increased levels of cliff erosion down the coast as the protective sand is not being replenished. - Existing defences have reduced sediment supply even further. Usually, sediment from the Holderness coast typically ends up being washed up in the Humber Estuary, where it contributes to the formation of tidal mudflats, without this sediment supply this cannot happen, and the risk of coastal flooding increases. Some of the sediment is also usually transported to the Lincolnshire coast where it replenishes beaches. Without this supply, the coast is more vulnerable to erosion. - The protective schemes have resulted in the formation of bays in between protected areas. As a result, wave energy is starting to be focused on the headland areas where existing defence schemes are being implemented. This increases erosion further, and also the cost of maintence, to such point where it may no longer be cost effective. - Lastly, all these factors combined make for the overall coastline defence schemes being unsustainable. Overtime, erosion will take place and the defence schemes will become obsolete, and the initial problems will arise once again, making original efforts futile. In this case, it may be more beneficial to consider soft engineering approaches such as the creation of marshlands or coastal realignment to help restore some of the ecological damage as well as try an alternative and more sustainable coastal management approach. SUMMARIZE: - Groynes prevent sediment supply downstream which erodes other cliff areas. - Reduces sediment supply to Humber estuary and Lincolnshire coast, increases flooding & coastal erosion at Lincolnshire. - Protected areas are forming bays in between each other, focusing wave energy at headlands and increasing erosional power of waves, making maintenance more and more costly. - All these factors combine to make the approach overall unsustainable in environmental and economical terms. |
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List the types of hard engineering used at a named area.
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Holderness:
- Towards the upper coast; sea defence walls employed to combat headland wave concentration erosion. (this reflects wave energy and can be bad). - Towards the middle coastal stretches, the use of groynes and gabions have been used. The groynes help to maintain current beaches and cause them to widen, also reducing sediment supply to other areas such as the Lincolnshire coast and Humber estuary. - Towards the lower portion, a combination of sea defence walls, revetments at the Gas Terminal, as well as gabions have been used, with the recent addition of rip rap in areas at Spurn point where wave concentration particularly during storm periods damaged previous hard engineering schemes, using rip raps to help supplement remaining defences. |
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Evaluate the success of hard engineering in a named coastal area.
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Holderness has adopted hard engineering schemes to help manage its coastline:
- Throughout they have used groynes which help to widen beaches and maintain them, but they are known for reducing sediment supply downstream, in particular to the Lincolnshire coast, where the reduction of replenishment means the coast is now more vulnerable to coastal erosion. Some of the sediment supply also used to be washed into the Humberland Estuary, where it contributed to the formation of tidal mudflats and eventually marshlands. Without this sediment supply, the marshland will not be able to completely form and as such coastal erosion will increase in frequency. - The protection of local areas in particular has lead to the formation of bays in between these areas. As this happened, increasing erosion as wave concentrate at the headlands, making existing defences more stressed, and raising the cost of maintenance to a point where it is no longer becoming a sustainable option. - All in all, the options described appear to have made for an overall unsustainable approach. The sediment supply 'cut-off' from the groynes will hamper natural efforts to reduce coastal erosion such as the marshlands which could have developed from the tidal mudflat formation, and the constantly rising cost of maintenance in headland areas formed by protected local areas means that the approach is unsustainable in both environmental as well as economic terms. SUMMARIZE: - Groynes trap sediment; cut off supply; increase coastal erosion elsewhere. - Reduction in sediment supply hampers replenishment at Humber estuary & lincolnshire coast; increasing flooding & coastal erosion. - Bays have formed in between locally protected areas; increasing erosion at headlands and subsequently increasing cost of maintenance of schemes situated in such affected headland locations. - The combination of the above points makes the scheme unsustainable both economically and environmentally. |
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Describe the future propositions taken to manage a named coast.
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Holderness has proposed a number of hard-engineering schemes for the protection of its coastline:
- 'Hold the line' approach at populated stretches, 'do nothing' approach at unpopulated coastal stretches. This has made property and land owners unhappy as it will significantly de-value their investments and threaten the safety of the few that do live in these areas. - Artificial offshore concrete-filled tyre reef been proposed to act as a breakwater by absorbing wave energy, has been proven successful in USA. No evidence to support this as of yet, but locals are against this idea because they feel it may disrupt natural processes and ecosystems, ultimately hurting the environment. - Sea defence wall proposed to be built at the Eastern Gas Terminal, costing ~£5 Million. This will reduce sediment supply to the nearby southern village, of population ~700, ultimately causing damage by increased coastal erosion rates. Propositions have been put forward to extend this, to encompass the village, but this will cost a further £2 Million and experts debate whether this justifies extra cost based on their cost-benefit analysis. - Coastal realignment proposed, by relocated businesses such as caravan parks and so forth further inland. Problems with this approach is that they don't know how to compensate the businesses for their relocation adequately and that some businesses can't physically be moved, due to geological circumstances such as farmland. As such, complications may arise and officials fear that the businesses won't find the relocation to be worth the hassle and might just downright leave the area, finding establishment elsewhere. If this happens, the economy will be impacted significantly. |
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Describe soft engineering approaches performed by a named coastal area.
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Blackwater estuary has adopted a number of soft engineering approaches to manage its coast:
- Coastal realignment schemes have been put in place. A number of sea defence walls have been lowered, this encouraged flooding and the subsequent formation of marshland through colonizing vegetation on tidal mudflats. A new and lower sea defence wall was built on higher ground, further inland, to protect inland areas from flooding. - A number of beaches have been nourished such as the Mersea Island. This also provides a sediment supply to areas where sediment is transported via longshore drift, adding material and absorbing subsequent wave energy and overall reducing coastal erosion elsewhere. - Marshes at Ray Creek have been stabilised through the use of adding brushwood and stakes, as this encourages sediment build up. SUMMARIZE: - COASTAL REALIGNMENT Breach 3 defence walls; encouraged marshland creation. (+ Smaller wall built to prevent flooding). - Beach nourishment; provides sediment supply. - Marsh Stabilisation ; adding brushwood & stakes, encouraging sediment to build up and become trapped. - Marsh creation, stabilization & beach nourishment. |
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Why is this soft engineering approach more sustainable than hard engineering options?
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---General Comments---
As a whole, hard engineering is very costly. It takes both a lot of time and money to construct as well as maintain hard engineering schemes, and most are considered to disrupt and ultimately damage natural processes and ecosystems. Soft engineering, on the other hand, works to integrate itself with the natural environment and processes, working to nourish and protect ecosystems through the use of defence options like marshland creation through coastal realignment as well as dune regeneration. Rather than disrupting natural processes, soft engineering works to integrate with them. It takes a lot less time and money to construct and maintain soft engineering schemes as nature does most of the work, and with the benefit that it is not as affected, even improved in some cases. Because of this, soft engineering can therefore be considered a much more sustainable option in both environmental and economic terms. ---Specific to Blackwater Estuary--- - The schemes are much more sustainable in the long term. Take the sea defence wall protecting local farmland for example, this would cost £600,000 to repair, and it costs just as much as the value of the farmland itself, unjustifiable in a cost-benefit analysis scenario. By breaching this defence and allowing for the formation of a marshland, nature will provide a more effective and low cost solution that will both be more affordable, require no maintenance as it is self-repairing, and overall much more beneficial to the environment. - The creation of more marshland areas also helps to nourish local ecosystems, providing more habitats for wildlife. - Despite efforts to realign the coast, some areas have yet to change into effective marshland, as vegetation have not yet colonized, and is debateable whether or not this will happen soon. Land for grazing animals and pasture has also been lost in this process. -SUMMARIZE- (specific to blackwater estuary) - Marshland creation less time, money, self-repairing, better for environment. (repairing defence wall too costly and less effective and worse for the environment). - Nourishes local ecosystems and provides more habitats for wildlife. - However, some efforts for realignment have not yet let to the formation of marshland areas. |
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What are some of the problems of a named hard engineering coastal management scheme?
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HOLDERNESS:- Groynes stop sediment supply; erode other coastal areas.- Protected areas form bays; more headland erosion; more maintenance costs for existing defences; unsustainable.- Due to reduced sediment supply, no more supply to mudflat at Humber estuary, or lincolnshire coast therefore more flooding and erosion.
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Describe the formation of dunes. |
- Longshore drift & Onshore current deposits material on the shore and accumulates it. - At low tides, this dries out, and prevailing winds transport it through saltation and suspension. - At the storm beach, the sediment gets trapped by litter and driftwood, causing it to deposit and built up. - Overtime, this forms embryo dunes closest to the shoreline. - These embryo dunes have characteristic high alkaline conditions, due to high salt content, and drain easily, with high wind speed. Only pioneer species such as marram grass may colonise the dunes. - When vegetation colonizes the dunes, it helps to stabilise them by providing an extensive root system which binds to the sand. As well as helping to trap sediment above and allow more sand to accumulate. - If no vegetation colonizes, the process of the prevailing winds allows the dunes to migrate inland, where they increase in size and progress in sequence from embryo dunes to fore dunes, yellow dunes, grey dunes, dune slacks and lastly, mature dunes which can reach up to 10m in height and ofter much gentler conditions for the vegetation. KEY: - Deposition on shore - Low tide dries - Prevailing wind transport - Trapped by little on storm beach - Embryo dune - Vegetation stability - Migration inland - Progression through dunes - Finally mature dune. |
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Discuss the migration of dunes. |
Embryo Dunes > Fore Dunes > Yellow Dunes > Grey Dunes > Dune slacks > Mature dunes. Embryo dunes - High alkaline pH 8 - High wind speed - Colonised by marram grass only, if anything. Fore Dunes: - Slightly lower pH 7.5 - Slightly taller - More vegetation of marram grass with other species, making it more stable than embryo. Yellow Dunes: - Even lower pH and more favourable conditions for vegetation to grow. - Can reach up to 80% coverage with mostly marram grass but some lichens and mosses. - Some mammals such as rabbits may begin to colonise. Grey Dunes: - Organic material starts to decay more, leaving a dark top layer which is visible. This provides nutrients to the soil and allows for the introduction of more different types of vegetation species. Dune Slacks: - Occur inbetween the grey dunes and mature dunes where the water table is closest to the surface. - They are formed as a result of the positive feedback of the wind removing sediment from the dune trough such that it eats into the ground below the water table, leaving an area of permanent surface water. Mature Dunes: - These are the tallest, reaching up to 10m - Most biodiversity variety is here - Fertile soil can be developed overtime which allows for the colonisation of even more vegetation such as birchwood trees even. - They are the gentlest conditions with the most acidity and lowest wind speed.§ |
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How are spits formed? |
- Formed in areas where the direction of the coastline suddenly changes such that it leads into a zone of low energy. - Longshore drift transports material along the coastline, and when it encounters a characteristic break in the coastline, it starts to project outwards into he sea. - Deposition does not stop until it reaches an area such as a river estuary where the material is removed faster than it can be deposited. - On the spit itself, the ends may become hooked due to changes in the direction of the prevailing winds - On the spits themselves, dunes may migrate and allow vegetation to colonise such as marram grass. - Behind the spits, sediment and mud is trapped, which may develop marshlands overtime. - In some instances where there is no present river estuary, the bar may extend all the way until it joins with the adjacent piece of land, forming a tombolo with an enclosed lagoon behind. |
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How are salt marshes formed? |
Salt marshes are formed typically in areas where the water is stagnant and sediments and mud is allowed to accumulate, such as behind spit landforms. They tend to form at tidal mudflats. Marshlands require a steady supply of sediment which is typically given through rivers or the ocean. Tidal mudflats usually give way to marshland formation, as their low gradient encourages rivers to easily flow over them, depositing sediment as it does due to the high frictional contact. The mudflats also encourage flooding to occur which leads to even more deposition. At such point where the mudflats have elevated to the point where there are periods that the area is no longer submerged, vegetation may start to colonie, such as glasswort pioneer species, which can withstand high periods of submergence and high salt water content. As they start to colonize, they develop extensive root system to aim for the water table, and as they do they provide roots which stabilize the sediment by binding to it, and their stems and leaves help to slow waves down and trap and accumulate sediment on the surface. After a period of time, the land elevates such that the submergence periods are shorter in duration, and this allows for a more diverse selection of vegetation to start colonizing alongside the glasswort and spartina. Key points: - They require sediment supply from ocean / river - Can form behind spit or estuary where water is sheltered and stagnant. - They usually start developing on these tidal mudflats, rivers flow on them due to low gradient and deposit. - Rivers flood and deposit more. - Pioneer species like glass wort colonize which can withstand high salt water content - Their roots stabilize and stem and leaf trap sediment - They elevate marsh such that submergance periods are shorter, more diverse types of vegetation colonize. |
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What is a berm? |
Berm is a ridge of sand caused by swash at high tide. |
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What is a runnel? |
An area of grooves running parallel to the shoreline caused by backwash.
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What is a cusp? |
Crescent shaped indentations which occur in beaches with high tidal ranges - not known exactly how they are formed. |
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What is isostatic sea level change and outline the different ways in which it can occur.
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Isostatic is change in land height level relative to the sea. Caused by: - Tectonic plate uplift or depression, occurring typically at the plate boundaries - Compression or Decompression of the earth's surface due to the formation or melting of ice sheets on the surface. - Abstraction of groundwater on land such as draining saltmarshes, which can cause the land to shrink and reduce in height. |
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What is eustatic change and outline the different ways in which it can occur. |
Eustatic sea level change is the change in sea level height relative to the land and is caused by: - Changes in climate - increase in temperature can cause glaciers and ice to melt, increasing the sea level. Decreases in temperature can cause more precipitation to fall as snow, adding to the glacial volume and reducing the sea level. - Tectonic movement which may alter the shape of the basin and allow a larger volume of water to occupy the same area of land, meaning that there would be a lower sea level. |
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List different methods of hard engineering |
- Gabions - rock filled cages - Riprap - boulders piled along the coast - Tidal barrier - Tidal barrage - Revetment - Sea defence wall - Breakwaters - Groynes |
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list different soft engineering methods |
- Beach nourishment - Beach stabilization - Dune regeneration - land use management (to protect dunes) - Marshland creation - Coastal realignment |
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What are some emergent features?
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- Raised beaches - raised beaches or wave-cut platforms as a result of isostatic or eustatic changes. Can form relic cliffs behind this as well as arches, stacks, stumps, geos, caves and so on behind. |
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What are some submergent features? |
- Rias - partially submerged river valley which is deep and wide at the mouth but gets narrower and shallower as you progress inland. - Fjord is a partically submerged glacial valley which is deep and narrow at the source but gets narrower and shallower towards the mouth, with a maximum height at what is called the threshold. - Dalmation coasts. Where valleys lie parallel to the coastline, isostatic rise or eustatic fall can lead to the partial submergence of the valley such that their peaks are only visible, leaving behind islands parallel to the coastline. |
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Describe the charactersitics of constructive waves |
- They are typically formed by distant sources such as distant storms. - They have longer wavelenghts, shorter waveheights, lower frequencies than destructive waves. - They have a stronger swash than backwash, caused by the wave creeping up the shore line and having enough time to percolate, depositing sediment. The backwash does not have enough energy to remove all of the deposited material, leading to a gradual build up of material on the beach. |
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Describe the characteristics of destructive waves |
- Shorter wavelength - Larger wave height and frequency - Greater energy and caused by more violent, local sources like nearby storms. - larger fetch, more wind energy. |
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What is a sediment cell? |
A localized area of a given source of sediment. This is defined as an area which supplies the coastline with replenishing sediment such that the supply will not be significantly impact if other nearby coastal areas are disturbed through physical or human causes.qe |
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Describe the different sources of sediment that the coast may have. |
- Biogenic input, such as that of sea life e.g. shells and so forth. - Coastal erosion characterised by marine processes and wave quarrying which may transport sediment and act as a source of sedimentation. - Sediment transported by rivers, and wind such as in the case of dune formation. (saltation and suspension). - marine deposits which may be transported via longshore drfit or onshore by the tide. |
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List the different ways in which weathering can affect the coastline. |
- Subaerial weathering (This is weathering which occurs without action of the water) such as: - Freeze thaw (water freezes and expands) - Biological weathering (animals burrowing) - Pressure release (overburden stripped away) - Chemical weathering (they are common where there are alternating periods of wetting and drying, or at the bottom of a cliff where there is soil and moisture.) - Oxidation - Hydration (rocks swell and decompose easier) - Carbonation (carbonic acid from acid rain attacks limestone and washed away by dissolving in water) - Solution - water dissolving rock - Organic weathering - human acids derived from plant decay contain important elements like iron and magnesium which contribute to weathering. - Acid rain - co2, suplhur dioxide and nitrogen oxides released by human activity form solution acids in the atmosphere and fall as precipitation making rocks like limestone most vulnerable to weathering, this is also a similar process to how carbonation occurs. |
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Describe the factors which affect wave energy. |
These are mainly determined by the wind: - Fetch (distance over which the wind is blowing) - Wind velocity - Duration of blowing of wind. Those with higher energy tend to form destructive waves, those with lower energy tend to form constructive waves. |
