Exploring coasts as dynamic and changing systems
Physical geography of Ghana
Ghana is located in West Africa and is boarded by Côte d’Ivoire to the west, Burkina Faso to the north and Togo to the east. The eastern edge of the country is dominated by the River Volta which flows into the Atlantic Ocean. Ghana’s coastline is 540km and makes up approximately 7% of the country’s land mass. 25% of Ghana’s population live on the coast and 70% of the country’s industries and businesses are located there.
Longshore drift in Ghana
Due to the strong prevailing wind from the south west over the Atlantic Ocean and the power of large waves which reach the coast of Ghana, there is significant and sustained longshore drift. As a result a massive amount of sand is transported by the process of longshore drift from Ghana to the coast of Togo to the east. Before the construction of the Akosombo Dam the River Volta would deposit huge amounts of sediment at the mouth of the river at the delta. Although this sediment was transported by significant longshore drift, the regular and constant deposition protected the coastline.
What impact is human activity having on Ghana’s coastline?
The construction of the Akosombo Dam in 1965, 60km north of the mouth of the River Volta regulates the flow of the River Volta and subsequently the transportation of sediment into the Volta Delta. Very little sediment now reaches the delta, because it is held in Lake Volta created behind the dam, but the strength of longshore drift remains the same. As a result, not enough sand is being deposited to replace the sand transported by longshore drift leading to coastal erosion and coastal retreat.
What was Ghana’s coastline like before the Akosombo Dam was built?
The coastline was dominated by wide deep sand beaches that were naturally replenished with sediment transported from the Volta Delta.
Why is the town of Keta under threat from coastal erosion?
The coastal town of Keta is under threat of coastal retreat due to the process of erosion. It has been estimated that 1 million cubic metres of sand per year is being removed. In the last 25 years, Keta, located 30km east of the Volta Delta, has experienced the removal of its protective beach which has left the town very vulnerable to coastal erosion. It is under threat due to the process of longshore drift which is transporting and removing sand from the town’s beaches. One of the reasons for this is the decrease in fluvial sediment (from approximately 71m₃/year to only 7m₃/year) reaching the Volta Delta. Previously, this sediment was transported and deposited on beaches to the east of the delta creating protective beaches which helped limit coastal erosion.
What has been done at Keta to protect the coast from coastal erosion and how might this help?
There has been some attempt to slow the process of coastal erosion at Keta with the introduction of groynes and a sea wall in 2002. The construction of the Keta Sea Defence aims to intercept longshore drift between Keta and Hlorve in an attempt to interrupt sediment transportation, encourage deposition and limit coastal erosion. The Sea Defence (sea wall and 8km road between Keta and Hlorve to re-establish the barrier link destroyed by erosion) together with an offshore breakwater and series of groynes has limited erosion by stabilising the coast. In addition, a feeder beach between the groynes is increasing the amount of sand for longshore drift to transport. It is worth noting however, that while management strategies seem to be halting the effect of coastal erosion at Keta there is still a problem of sustained coastal erosion on the coast of Togo and Benin due to the disruption to longshore drift.
The United Arab Emirates
The United Arab Emirates (UAE) boarders Saudi Arabia to the south and Oman to the east. It has a coastline on the Persian Gulf and is located on the Arabian Peninsula. UAE is made up of seven Emirates. The largest Emirate is Abu Dhabi which as well as being the capital is also a centre for business and industry. The other large business centre is Dubai.
What are the main reasons for land reclamation in the United Arab Emirates?
Industry in Dubai had been based on oil but the government was aware that oil reserves would not last forever and that they would have to diversify to sustain economic growth. One of the new industries was tourism. However, with a limited coastline, the government decided to undergo a series of coastal land reclamation projects. Land reclamation usually involves dredging sand and sediment from the sea bed and using it to build new land in the sea.
How is human activity changing the coastline of Abu Dhabi and Dubai?
Land reclamation has dramatically changed the shape and length of the natural coastline. Abu Dhabi’s coastline continues to expand as a result of land reclamation. Examples of areas which now exist due to land reclamation include the Al Raha Beach development and Lulu Island. Dubai only had 70km of coastline so they decided to undergo huge land reclamation projects to expand the coastline and develop luxury residential areas as well as the development of leisure and recreational services. In 2005 Palm Jumeirah was completed. The man-made island consisted of an estimated 110million m₃ of dredged sand. Since then there have been a large number of other land reclamation projects including ‘The World’ which used 325 million m₃ of dredged sediment. Today there is approximately 1000km of coastline; 14 times as much as there was originally.
How were the new man-made islands created?
The man-made islands were created by dredging sand from the sea bed and using it to fill in coastal salt flats called sabkhas. Examples of areas built on sabkha flats include The Mussafah Industrial Area and The Industrial City of Abu Dhabi.
What negative impacts have Abu Dhabi and Dubai experienced as a result of land reclamation to build new islands?
Land reclamation in the UAE has had a number of economic benefits (more land available for infrastructure and development, growth of tourist industry, development and sale of expensive real estate) but both Abu Dhabi and Dubai have experienced negative impacts of this large scale artificial coast creation.
Marine ecosystems have been altered as a result of the dredging and land reclamation process which has buried coral reefs and oyster beds with sediment. These features were habitats to marine animals and as a result there has been a breakdown in the ecosystem and a decrease in commercial fishing. The coral reefs also acted as a natural barrier to the waves and helped limit coastal erosion.
The location of the man-made islands has also led to the loss of many of the country’s salt flats, which has removed natural habitats and had a negative impact on flora and fauna. For example, the loss of habitat for the Socotra Cormorant, a rare sea bird.
Other problems include coastal erosion of UAE’s natural beaches. In Dubai, The Palm disrupts the natural pattern of longshore drift as waves are forced around the structure and as a result less sand is being transported to and deposited on the natural beaches at Jumeirah. Consequently, there has been accelerated coastal erosion in some areas and significant deposition in others. Although a breakwater barrier has been constructed to protect The Palm, this too is under constant threat of coastal erosion as the sea fights to return to its natural state.
Working in small groups you need to consider how humans can change coastlines. You can refer to any images used in the unit so far. Feedback your ideas to the rest of the class.
You will be given information on one of two case studies; either longshore drift in Ghana or land reclamation in the United Arab Emirates. Working in your group you need to use the research sheet to answer the questions on the relevant case study sheet. You can use any other information, for example from atlases or Google Maps, to supplement your answers.
When your group has completed their case study sheet one student will need to move to a group who has looked at the other case study and teach the group what they have learnt. That group should then be able to complete the second case study. Your group will also receive a ‘teacher’ from a different group so at the end of the task all groups will have two completed case study sheets; one for Ghana and one for the UAE. When your original group member returns to the group you have to teach them about the new case study you have learnt about from your peer.
Two groups then come together who have looked at different case studies to be given the opportunity to ask questions of the case study you did not originally research. You will be asked to share with the class one new aspect of the lesson that you have learnt about that you didn’t know about before the lesson started.
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