Head Sea Defences

Published: 2021-07-01 04:36:55
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Category: Water, Beach, Dune

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There are two long groynes here. These are really effect at doing their job. Although it is not clear from the image how well these work, if you go there you will see it quite evidently how well they do their jobs. In some areas with long groynes, there have been large parts of beaches rebuilt. They are made out of rubble in order to slow down the weathering caused by the waves hitting the groynes. These work by stopping sediment from being dragged across the shore by the effects of Longshore drift. Their sole purpose was to protect the beach what was already there but have surpassed expectations and added a lot of material to the beach.
For a clear understanding of all the different sea defences I did an evaluation of the effectiveness and Environmental (looks). Looking at the graph, there is no doubt that the groynes are effective at what they do. For the effectiveness they received the highest rating of 2. The size of the beach been restored back and the amount protected is a large amount. With a total mark of 3 from a potential 4, it is definite that the groynes are assisting in the protection of the beach. The groynes did lose a mark for the way they look aesthetically. Being a tourist destination it was important that Hengistbury Head is pleasing to the eye.
200m Gabion:

At the top, there is an image of the 200m Gabion which has been built at the South Cliff. The result of placing the Gabion here is not clearly seen but an explanation will be given. The Gabion at Hengistbury Head is a long cage which has been put in place to hold back the rocks that have been filled behind them. Also the cages absorb the force of the waves and hold back the material behind them. The Gabion is working brilliantly to protect the South Cliff. The people walking on the land at the top of the cage would not be able to walk there if it wasn't for the Gabion.
The Gabion prevents slumping which stops the material falling onto the beach and keeps it in one steady place. The gabion stops the waves eroding the ground further down. There is a footpath which is not visible in this image. This footpath wouldn't be there since the waves would have reached there if the Gabions weren't built and eroded the rocks and made large cracks, making it dangerous to walk on. In the end the purpose of the Gabion is to stop the waves force reaching too close to the land and destroying it.
As a total score, the 200m Gabion faired quite well, but not too well. This is because of the -1 it received for its Environmental Score. After understanding how the Gabion works the picture displays more than clearly that the effectiveness of it is brilliant. It does what it is supposed to do more than perfectly. It has prevented the waves from reaching inland and in doing so ensured that the South Cliff remains safe. The Environmental Score for the 200m Gabion was very low. This is because it conflicts with the natural beauty at Hengistbury Head. This is because it is clear that it has been placed there and looks out of place at the Top of the beach.
Rubble Groynes:
This is a plan view of the East facing cliff and the groynes that have been built to prevent Longshore Drift. Unlike the other image, this image shows very clearly how the groynes have affected the beach. The red arrows point out the sediment that has been caught thanks to the groynes. It might not look like much but if you consider the material each groyne has picked up, it adds up a lot. These groynes have the same purpose as the gabion, i.e. stop he waves from eroding certain parts of the beach. The groynes prevent the waves from carrying beach material out to sea. This eventually builds up to a major part of the beach.
At the top there is a graph portraying the evaluation the gryones received. Since there were so many groynes present, I worked out the means by assessing each groyne then calculating the mean. The total score of the groyne is similar to other defences, but the other defences lost marks due to the way they look and at the same time gained marks from their effectiveness. The image does show that the groynes are working well, but there is more that needs to be taken into consideration.
Since the groynes are just piles of rubble, it is more than likely that a piece of rock will be taken out into sea by a strong wave causing the rocks on top of it to tumble and fall. It will also not be able to withstand the force of powerful waves. They could crumble during a storm completely. This defeats their purpose since they are most needed during storms since that is when most material is taken out to sea. Environmentally the groynes would have got a higher score if they were not so many of them present. The natural beauty of the East Cliff is questioned when so many of these groynes are built
Sand Dunes:
The sand dune at the top here is present at South Cliff. These are naturally occurring and have a wide range of sizes. They can be anything from small hills to huge mounds. They are most commonly found at the top of beaches. These are formed when winds lift the sand from the beaches surface and are blown to the top. The sands are caught by materials that come in their way such as driftwood. Over a long period of time, the sand keeps getting deposited in the same area. This eventually grows bigger and bigger and builds up into big mounds. These dunes are a perfect place for vegetation such as Marram Grass to mature and thrive successfully. Some wildlife might also be found to nest in these dunes. These dunes are extremely prone to erosion naturally as well as human contact. These dunes absorb the force from powerful waves keeping things behind them safe.
At the top you can see the sand dunes scored top marks, the best score compared to all the other sea defences present at Hengistbury Head. Because the dunes form near the cliff and are so big (in most of the cases), it protects it from erosion from the sea. Because of this I though the sand dunes deserved top marks for effectiveness. Since they form naturally it definitely deserved top marks for Environment as well. These dunes do not look out of place since they are formed from material that is found at the sea. They blend into the surroundings perfectly and add to the natural beauty of the South Cliff.
At the top here you can see an image of the causeway at the East Cliff. From the picture here you can see that the causeway is having no effect at all on the beach. It is just present there. It is a pointless waste of money, time and effort. It was put there in the intention to work like the gabion cages i.e. hold the east cliff back. Since the causeway was placed at a ridiculously low height there is no effect at all in preserving the beach.
The causeway has scored the worst compared to all the sea defences present at Hengistbury Head. It achieved an overall score of -3. As you can see from my above explanation there is no reason why the causeway should get a higher score. The causeway could possibly have been a great sea defence but the fact is that this was certainly not the right place for it. It got the lowest effectiveness score for this reason. Environmentally, I did not give it the worst possible score since looking at the picture carefully, if it wasn't built there, some people could have difficulties coming down from such a tall gabion. It could possibly be used as a step from the top of the gabion to the beach surface. That is why I think it did not look that bad environmentally. The first time I saw it, I thought it was built for that purpose. Overall the causeway was a total waste of time, effort and money that could have been used for other ways of protecting Hengistbury Head.
Drainage Weir:
At the top you can see an image of the drainage weir present at East Cliff. The drainage weir looks like a waterfall. It is man-made and fulfils an important purpose. The purpose of the drainage weir is to drain out and down all the water (more specifically rain water) from the cliff to prevent it from becoming to saturated. If it ever does get over saturated the outcome could be major slumping. In this image you can see the drainage weir working at optimum. This is because the day we went, it was raining quite heavily. Vegetation grows very well next to the drainage weir due to the large amount of fresh water that flows from the top. Marram grass grows very well around it. The Marram grass also helps since it holds the sand together and stops it from eroding and falling. Looking at how effective it is in the weather this picture was taken in, it shows how effective it is.
The bar graph here shows that it is as effective as the sand dunes. It has also scored a 4 out of a possible four. The effectiveness is unquestionable as you can see in the above image. The sheer amount of water flowing down from the top shows its effectiveness. Without it, there would definitely be a problem with slumping. It also got top scores for environmental since it does look very good. Being a man-made object, it perfectly fits the environment and at the same time fulfils its purpose.
Gabion Cages:
At the top you can see an image of the gabion cages present at the East Cliff. If you look clearly at the image, you can see some sand at the bottom of the causeway. It is very clear that the gabion cages are doing their job. These gabion cages are filled with rocks just like the other ones. The gabion cages absorb the impact from the waves and holds them back, preventing them from reaching the east cliff and eroding it. They are doing exactly this but they are doing it well. They are stopping material being dragged into the sea and preventing erosion of the east cliff. The gabion cages have been placed on top of the causeway in order to have a much higher height. Also the causeway is not tall enough to protect the cliff. The cliffs have started to slump but the gabions have managed to drastically slow it down.
At the top you can see an image evaluating the Gabion Cages' Effectiveness and Environmental. The total score being a 0 is not that good. The score was mainly affected by the Environmental rating, since it looked out of place completely and harshly affected the natural beauty of the Eat Cliff. Considering all this I decided to give it a -1 for an Environmental rating. It would have got a much better score if it wasn't for the presence of the cages and ruining the final outcome, but removing the cages would allow the rocks to fall over. The gabion cages are definitely effective as you can see in the photo. But I still have it a rating of 1 instead of 2 since there is some material creeping over them. This is quite bad since over a period of time the Cliff could slump over the gabion cages.
Rip Rap:
At the image at the top you can see an image of the Rip Rap which is visible at East Cliff. Rip rap is basically a lot of rocks scattered along the beach in order to absorb the energy from very strong waves and breaks them before they reach the cliff base. This type of sea defence is very cheap to put into action but at the same time it is extremely effective. It is a very good way of reducing the damage that might have been caused if powerful waves were allowed to get to the cliff base. Because of its effectiveness it slumping caused by undercutting is very unlikely to occur and because of this expensive ways to reduce slumping can be not put in place too often. In the end the rip rap is a perfect all round way of defending the cliff base and reduces slumping.
At the top you can see an image of the Rip Rap's (present as South Cliff) score for its defence evaluation. It got an overall score of 2 which it deserved quite fairly and is quite a good score anyways. I gave it a score of 1 for its effectiveness because there were not any excessive amounts of slumping at the South cliff where the rip rap was present. Environmentally the rip rap fitted in its environment and blended in quite well but since it was fairly obvious that the rocks were placed there since the boulders were quite large and they were not any visible cracks on the cliff big enough to fit any one of the large boulders. But it did blend into the surroundings very well. The natural beauty of Hengistbury Head was not affected by the rip rap.
Sea Wall:
The picture at the top is an image of the Sea Wall at Mudeford Spit. Sea Walls vary in size and materials in which they are made from. The sea wall at Mudeford Spit is made of large concrete slabs that have been laid on top of each other. They have been place next to the beach huts to protect them from all types of waves that could potentially erode the ground on which the huts are built on. They are barriers against weak and strong waves. Unlike some other sea other defences like the gabions, the wall does not absorb any of the waves but just prevents the waves from reaching far ahead up the beach.
The sea wall breaks the waves before they reach the huts, so even if they go above the wall the water will just spray on the huts. But if a tall and powerful wave does have the force to cover enough distance to reach the huts then it is very likely for the huts to get damaged since if it had enough force to reach up to the huts then it will definitely have enough to cause some serious damage. This is a problem because of the rather small height of the sea wall. But I think it is highly unlikely for a wave with that intensity to reach Hengistbury Head but due to the effects of Global Warming there can never be any assurance.
At the top you can see an image of the evaluation the Sea Wall received based on its Effectiveness and Environmental. Mudeford Spit's natural beauty was already tarnished thanks to the littering, vandalism and beach huts but now thanks to the sea wall, the little left beauty has vanished. The Beach huts definitely stood out but kind of fitted into the area but this concrete slab wall does not fit in at all. It got an Environmental score of -2 for that reason. It did not deserve anything higher. I gave it a rating of 1 for its Effectiveness, because it definitely does what its suppose to do without any problems, but I didn't give it a two since it would've have been better if it was higher. This would have made the beach huts feel a bit safer. But the huts are still standing strong because of the sea wall. The final score the sea wall received a -1. The environmental score dragged the score down a significant amount.
Beach Nourishment:
At the top you can see two images. Both of them are images of the equipment needed to perform Beach Nourishment. Beach Nourishment is a simple idea which entails taking sand from a source (usually another beach) and dumping it into the beach which requires nourishment. This process is important because although most of the sea defences might be working efficiently to tackle the beach erosion, there is still a lot of sand that is carried out into the sea because of the waves. It is sometimes needed in order to widen a beach.
This method doesn't stop erosion but simply replaces what has been lost by the waves. It balances the amount of sand on the beach because the areas of the beach are unlikely to lose similar amounts of sand. By replacing the sand from the worst affected area it makes the beach look more pleasing to the eye. A problem with this method is that the sand needs to be continually replaced since the sand naturally on the beach erodes away slower than the sand that has been artificially added.
At the top you can see an image of the graph with the evaluation of Beach Nourishment. Beach Nourishment has also been awarded the top score with a four out of four. The Beach Nourishment is definitely an effective way of dealing with the wave's strong backwash. It allows the artificially added waves to be carried out the beach rather than the natural sands. And for Environmental, it deserved a two because it just replaces what needs to be there. It makes the beach look more complete. The only environmental effect it has on the beach is to improve it.
The various groynes seen in the satellite image below can be found at Mudeford spit. Looking at the image below you can see just how effective these groynes really are. They are doing a fantastic job of stopping the sediment in the waves from moving down the beach. The sediment is being carried down the beach by nothing more then long shore drift. Although long shore drift created Mudeford spit it could also destroy it or make it so big that the harbour becomes closed. For these reasons these groynes have had to be put in place.
Looking at the bar graph above overall the groynes have done very well with an overall score of 3 out of 4. Environmentally on Mudeford spit because it is so crowded by beach huts I do not think that the vast amount of groynes effects the natural appearance of Mudeford spit. Nothing short of perfect describes the effectiveness of these groynes it is truly amazing how much sediment they have trapped over the years.

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