Human Modifications at the Muriwai Coastal Environment You may be asked to explain how human modifications (or interventions) have effected Natural Processes. This may be in an essay or with the use of diagrams, or both. Remember the key here is the effect on natural processes. Be careful not to go into detail about the human intervention, that is not the purpose of the question. Remember to include sketches / diagrams / maps. A good example would be: “this shows the natural process before the human intervention. The next sketch shows how the Natural Process operates after the human intervention.
Human modifications at MCE and the processes that have been affected: * Human modification 1: Construction of Sea Wall A sea wall, called a Gabion Basket, has been erected at the southern end of the beach. This was constructed to protect the headland from further wave erosion and to ensure the pedestrian pathway stayed open for access to the headland. The wall is ____________metres long and was built in _________. * Processes affected: The main processes affected are wave refraction, wave erosion and coastal transportation. The waves refract around the headland and attack the sides of the headland.
Because of the sea wall the waves can no longer attack the side of the Otakimiro Headland. This means the waves no longer erode the northern side of the headland and material, such as Awhitu sand stone and volcanic rock are no longer eroded and deposited in to the sea at Muriwai. Because of the lack of erosion, the amount of sediment transported northward, up the beach, is also affected. This human modification and its impact on processes can be summed up in the following diagrams. (complete appropriate diagrams) * Human modification 2:
Construction of Revetment (boulders dumped next to sea wall at southern end of beach). Large, angular boulders have been dumped next to the seas wall at the southern end of the beach. This is to disperse the energy of waves as they refract and attack the southern cliffs underneath the car park. This is aimed to protect the cliff and southern dunes from further wave erosion. Processes affected: Wave refraction, wave erosion and coastal transportation are all affected. The boulders spread the energy of wave out – this is why they are angular boulders, as they dissipate or disperse the energy.
The waves with energy built up over the _________km fetch can exert up to ___________tonnes of pressure when they crash against a surface. The revetment slows down the rate of wave erosion in this corner of the beach and thus the processes of wave refraction and erosion are impacted. With less eroded material in the water, the rate of L. S. D. will also be impacted. This human modification and its impact on processes can be summed up in the following diagrams: (complete appropriate diagrams) Human Modification 3: Planting of Woodhill Forest (Pine Trees) behind Northern Dunes.
The Forest was planted in ___________. It main aim was to stop the retreat of the northern dunes as the trees bind the sand/soil. Processes affected: The trees have decreased the amount of ground water entering the Okiritoto Stream. This means less water flowing in the stream which means the stream can not carry as much sediment. This means less material is being carried out to sea to be used in L. S. D. The material from the stream is instead building up in its mouth – forming a small delta. This can be summed up in the following diagram. Human Modification 4: Planting of vegetation on dunes.
Marram grass has been tried but the most successful vegetation to trap sand and stop dunes retreating is Pingao and Spinifex. This is due to their long roots (finger-like). Processes affected: Wind erosion has decreased as has the amount of blowouts, especially on the northern dunes. The sand is trapped in the root system of the vegetation after saltation has taken place – this binds the sand together and slows the inland movement of sand. Diagrams to sum this up are… Human Modifications 5: People walking and driving on Muriwai beach and dunes Muriwai beach is deemed a public highway.
Over 1 million people are estimated to have visited Muriwai in 2008. Dunes are trampled by car traffic and foot traffic. The Auckland Regional Council has recently stopped traffic in the southern end of Muriwai Beach and fences and signs are now used to keep people off dunes. Processes affected: Trampling leads to loss of vegetation and increased blowouts. Wind erosion is increased and dunes start to retreat as the vegetation is unable to hold the sand together. Diagrams to sum this up are… Human Modification| Effect on natural process| Construction of Sea wall | Modified Wave refraction & coastal transportation & deposition.
Less sediment deposited into sea for longshore drift| Boardwalks and Paths on Otakamiro Headland| Slowed erosion and damage to vegetation : interfered with coastal transportation & deposition| Planting of Pinetrees behind Dunes| Prevented accretion, decreased ground water which has reduced ability of Okiritoto stream to carry sediment > deposited at stream delta > less sediment been carried out to be used for Longshore drift| People walking, driving along beach (estimated 1 million people visit each year)| Trample vegetation, erode dunes, lead to blow outs| Planting of Vegetation| Norfolk Pines, iceberg and marram grasses have been unsuccessful > not suitable for Muriwai conditions, Pingao & Spinifex more durable and suitable >> prevented blowout and Aeolian (wind) erosion| Construction of Infrastructure eg carpark, lifeguard tower, diversion of stream| Prevented dune encroachment inland, southern dunes at mercy of sea intrusion|
