Coastal System Analysis (Coastal erosion)

Coastal erosion is a natural phenomenon, which has always existed and has contributed throughout history to shape coastal landscapes. Coastal erosion, as well as soil erosion in water catchments, is the main processes which provides terrestrial sediment to the coastal systems including beaches, dunes, reefs, mud flats, and marshes. In turn, coastal systems provide a wide range of functions including absorption of wave energies, nesting and hatching of fauna, protection of fresh water, or siting for recreational activities. However, migration of human population towards the coast, together with its ever growing interference in the coastal zone has also turned coastal erosion into a problem of growing intensity.

Understanding the key processes of coastal dynamics and how coasts developed in the past and present, as well as over the short and long term, is very important for managing coastal erosion problems because coastal erosion may occur without cause for concern. This can be very complex and possibly controversial where many conflicts of interests exist within the coastal environment. The main underlying principles for coastal erosion management are as follows (NRC, 1990; ARC, 2000):

a.       Identify and confirm coastal erosion as a problem.

b.      Identify, confirm and quantify the cause of the problem and ensure that any

c.       Management option is well thought out before implementing coastal erosion measures.

d.      Understand the key processes and characteristics of coastal dynamics and

e.       System boundaries that reflect the natural processes of the erosion problem.

f.       Determine the coastal erosion measure options and implement them using proper design, construction and maintenance with careful evaluation of the effects on adjacent shores.

From sea erosion problems that occur, there are several options that can be done to prevent or resolve these problems by doing the following three things:

1.      Coastal Stabilization With Breakwater

Stabilizethe beach can with breakwaters constructed,. Breakwater for energy reduction wave that hit the shore can be done by making the building a breakwater parallel to the beach (Offshore Breakwater). with the breakwater wave coming to hit the beach was broken at a place some distance from the shore, so the wave energy up the beach is quite small.

Revetment is one bnetuk breakwater. Revetment is made coastal protection structures parallel to the beach and usually has a sloping surface. Regular structure consisting of concrete, stone heaps, sandbags. Because the surface is made up of heap/concrete block with voids in between, it is more effective revetment to reduce wave energy. Construction strengthening coastal cliffs serves to protect land or buildings behind the wall/revetmen from the onslaught of the waves, so that the soil is not eroded. Revetmen used for protection against the relatively small waves. The downside of this is the possibility of building a fairly deep scouring at the foot of the building. Therefore, at the foot of this building should be created as a protection against scour/erosion (toe protection) is quite good.

In addition there is a form breakwater seawall. Seawall almost similar with less revetment, which is parallel to the beach but the seawall has relatively straight or curved walls. Seawall is generally made of solid construction such as concrete, steel plaster/wood, masonry or concrete pipes so seawall did not dampen wave energy, but the waves were hitting the surface of the seawall will be reflected back and cause scouring at the heel.

Breakwater may also Useful to hold back the sea sediment caused by ocean currents (onshore-offshore transport). Eventually the suspended sediment to accumulate and form Tombolo, Tombolo it will serve as a sediment barrier parallel to the beach, but the establishment of this Tombolo take a long time.

In the area that represents the flow of the river and the surrounding settlements, on the banks of river rock walls can be made of iron frames. By making a stone wall with iron wire frame in a river can reduce the erosion of river water. This can be seen in the figure below.

Figure 1. wire mounting stone

In the picture above can be seen, its function is to reduce the erosion that occurs in the watershed. By using this iron wire to reinforce the stone structure. So that last a long time and to prevent flooding when the river water carried.

2.      Can planting mangrove forests (mangrove forest) in areas of sea erosion. Mangrove forests are tropical coastal vegetation communities, which are the characteristic littoral plant formations there did the tropics. Mangrove vegetation is dominated by a few species of trees that can grow and thrive in muddy tidal areas in Indonesia.

Physically mangrove plants can keep the shoreline in order to remain stable, preventing or protecting the beaches and river banks from erosion and to trap marine pollutant and waste, accelerate the expansion of the land, protecting the areas behind the mangroves of the blows and the waves and the wind from the sea, prevent the intrusion of salt (salt intrution) towards the ground, it can reduce the risk of tsunami, and assist in the deposition of silt so the quality of sea water is more awake than silt erosion and so on.

Lack way of resolving the problem of erosion associated with the crop planting mangrove vegetation can’t be done in all kinds of beach as mangrove only grows in muddy areas. While in Indonesia is that the coastal erosion is not only a muddy area only.

3.      Filling Sand is one of the sea erosion problem solving occurs. Charging sand aims to replace sand lost to erosion and provide coastal protection against erosion in the form of sand levee system. Things to consider is the location of the sand must have sufficient depth so that the increase due to the depth of excavation of sand does not affect the pattern of waves and currents, which in turn will lead to the erosion of the surrounding beaches.

Security system with the addition of coastal sediment supply to do with the "beach nourishment" that adds sediment supply (move sediment) from the ground or from elsewhere in the space will potentially eroded, or restore the eroded beach. The benefits of coastal protection system is that the implementation is simple, it requires material cost very much.

selection of underwater structures or filling sand as coastal protection, water structure has smaller dimensions than a continuous structure to the surface so it is more economical. Besides this, the structure of water is also not interfere with views of the beach area or travel to the ocean so it is suitable for a tourist area. In an alternative method of solving problems with filling sand sea erosion, the magnitude of the overall wave is not damped so that water behind the structure can still be used for swimming and other activities.

Bibliography :

Dahuri, H.R., Rais, J., Ginting, S.P., dan Sitepu, M.J., 1996.  Pengelolaan Sumber Daya Wilayah Pesisir dan Lautan Secara Terpadu, PT Pradnya Paramita, Jakarta.

Departemen Kelautan dan Perikanan RI. ,2004 , Pedoman Penyusunan Rencana Pengelolaan Garis Pantai.

Dharmawan, A.S., 1999. Tinjauan Geomorfologi Pesisir Teluk Balikpapan dan Dampak Penggunaan Tanah di Daerah-daerah Aliran Sungainya sebagai Salah Satu Pertimbangan Bagi pengelolaan. Bahan Lokakarya Partisipatif Proses Perencanaan Pengelolaan Teluk Balikpapan Bersama Pihak-pihak Terkaitnya, Balikpapan. 

Yuwono, N., 2004, Pedoman Teknis Perencanaan Pantai Buatan (Artificial Beach Nourishment), Pusat Antar Universitas, Universitas Gadjah Mada Yogyakarta.