Natural shield necessary to protect RI coastline<\/p>\n
Bambang M, Contributor, Jakarta<\/p>\n
A lot can be learned from the massive earthquake and tsunami that
\ndevastated part of Nanggroe Aceh Darussalam and North Sumatra
\nprovinces, on Dec. 26.<\/p>\n
Among other things, this natural disaster has reminded the
\npublic of the need to have a natural shield along the coast to
\nwithstand the devastating blow of a tsunami.<\/p>\n
If only the coastal area of Banda Aceh had had such a shield,
\nfewer people would have been killed in the disaster and much of
\nthe destruction of Banda Aceh would have been prevented.<\/p>\n
A natural shield might take the form of a mangrove forest, a
\ngreen belt or a coastal forest comprising various species of
\nsuitable trees.<\/p>\n
In addition, concrete fortifications could also be built along
\nthe coast to withstand a powerful tsunami. Such a concrete
\nstructure, however, would be costly to build and would not be as
\nstrong as a natural shield.<\/p>\n
Tectonic plates<\/p>\n
As Indonesia lies precisely over the meeting point of the
\nIndo-Australian and Eurasian plates, the country is close to many
\nunderwater epicenters that might cause a tsunami.<\/p>\n
Geological disaster expert Mas Atje Purbawinata said that
\nbased on the history of earthquakes and their setting, Indonesia
\nhad 28 areas prone to tsunamis, such as the coastal areas in
\nAceh, the western part of North Sumatra, West Sumatra, Bengkulu,
\nSouth Lampung, west and south Banten, the southern part of
\nCentral Java, North, Central and South Sulawesi, north and south
\nMaluku, Biak-Yapen, Fak-Fak and Balikpapan.<\/p>\n
Before the tsunami hit Aceh and North Sumatra on Dec. 26,
\n2004, 16 tsunamis had occurred across the country, with the worst
\nthree occurring in Flores in 1992, Banyuwangi in 1994 and Biak in
\n1996.<\/p>\n
A shield would be particularly appropriate for a coastal area
\nthat faces an epicenter,\" said Eko Teguh Paripurno, a lecturer at
\nthe school of geology, National Development University,
\nYogyakarta.<\/p>\n
Coastal areas that need such protection have shores that
\nshelve steeply into the sea, like the beach around Parangtritis.
\n\"In Yogyakarta's deep waters, a tsunami moves fast,\" said Eko,
\nwho is also an environmentalist.<\/p>\n
A dense mangrove forest in a coastal area would be able to
\nwithstand a tsunami. That is why one of the items on the working
\nagenda of the forestry ministry's Disaster Management
\nCoordination Team in Aceh province and North Sumatra is the
\nrehabilitation of the mangrove forests in these provinces (visit
\nwww. Dephut.go.id).<\/p>\n
\"One of the functions of a mangrove forest is to stabilize the
\nland,\" said Erny Poedjirahajoe, a mangrove expert from the
\nforestry school of Gajah Mada University (UGM). A mangrove forest
\nprotects the land from abrasion, seawater intrusion, wind from
\nthe sea and the tsunami itself.<\/p>\n
How mangroves protect the coast<\/p>\n
When the tsunami that followed the earthquake on Dec. 26,
\n2004, destroyed coastal areas in Aceh, North Sumatra and a few
\nother countries in South Asia plus Somalia in Africa, Bangladesh
\nsaw the smallest number of disaster victims.<\/p>\n
One of the reasons is that Bangladesh still has a vast
\nmangrove forest area,\" said Rudhy Pribadi, a mangrove expert from
\nDiponegoro University, Semarang. He said that the mangrove
\nforests in Bangladesh were properly conserved and served to
\nprotect the country's coastline, which is buffeted by 40 storms
\nevery year.<\/p>\n
In his 2003 thesis for his master's degree titled Mangrove
\nForests as Protectors of Coasts Against Tsunami Runup (a physics
\nmodel simulation) in the postgraduate program at UGM, Karuniadi
\nSatrijo Utomo indicates that a mangrove forest may considerably
\nreduce the energy and runup distance of a tsunami.<\/p>\n
A mangrove forest with 5 percent density, a height of five
\nmeters and a breadth of fifty meters will be able to cut 52
\npercent of the height of the tsunami, 38 percent of its energy
\nand 14 percent to 22 percent of its runup distance on the coast
\nwith slopes of five, 10 and 15 degrees.<\/p>\n
Meanwhile, in his paper written for the school of fisheries
\nand maritime sciences of Diponegoro University (2003), titled The
\nInfluence of Density and Breadth of Clumps of Mangrove in
\nWithstanding the Tsunami (a physics model simulation), M. Qodri
\nAgus writes about the important role of a mangrove forest in
\nreducing the destructive power of a tsunami.<\/p>\n
In this thesis he argues that the density of the mangrove
\nforest plays a bigger role in reducing the power of the tsunami
\nthan its breadth.<\/p>\n
Natural protection<\/p>\n
Indonesia has the world's largest mangrove forests, with 8.6
\nmillion hectares. About 3.8 million hectares are found in forest
\nareas while the remaining 4.8 million hectares grow in coastal
\nareas.<\/p>\n
Some of the mangrove species found in Indonesia are bakau
\n(Rhizopora spp), apiapi (Avicenia spp), pedada (Sonnerata spp)
\nand (Xylocarnus spp).<\/p>\n
Unfortunately, much of this natural shield has been destroyed
\nby man. Many mangrove forest areas along the country's coast have
\nbeen converted into fish farms.<\/p>\n
According to 1999 data of the directorate general of
\nrehabilitation of land and social forestry of the Ministry of
\nForestry, about 68 percent (some 5.9 million hectares) of
\nmangrove forest in Indonesia have disappeared.<\/p>\n
As many areas in Indonesia are prone to tsunamis, it is
\nimperative that mangrove forest areas are rehabilitated.<\/p>\n
Fishermen wishing to boost their income by establishing fish
\nhatcheries should avoid clearing mangrove forests.<\/p>\n
In fact, there is a mutually beneficial relationship between a
\nmangrove forest area and a fish farming pond. Mangrove leaves
\nthat fall into the pond become a food source for fish and
\nshrimps.<\/p>\n
\"The research that I have made on the northern coastal area of
\nJava shows that a fish farm made in a mangrove forest will yield
\nbetter results than a pond with no mangrove surrounding it,\" said
\nErny, who has planted mangroves on the northern coast of Java for
\na decade.<\/p>\n
Care needed when planting mangroves<\/p>\n
Although mangroves are effective in withstanding a tsunami,
\nErny has reminded the government not to be careless when
\ncultivating mangroves on the coast.<\/p>\n
Not all coastal areas are suitable for mangroves. The area
\naround the estuary of the Bogowonto River on the Congot coast,
\nYogyakarta, is prone to tsunamis but the planting of mangroves
\nthere has failed.<\/p>\n
\"I wish to call on policy makers to carry out research before
\ndeciding to plant mangroves in a particular area,\"Erny said. In
\nthis research, it is necessary to ascertain soil conditions,
\nsalinity and the time when there will be strong winds. \"If a
\nmangrove is planted when there is a strong wind, the seeds will
\nbe blown away by the wind,\" she added.<\/p>\n
In her experience, mangrove planting will fail if it is done
\nonly for the sake of carrying out a project. If little is done to
\ntake care after it is planted, only a small number of the
\nmangrove seeds will grow.<\/p>\n
Therefore, the coastal community must be directly involved in
\nmangrove planting. They must be assisted so that they will really
\nunderstand the benefit of such activities.<\/p>\n
Other plants are effective, too
\nAs not all coastal areas are good for mangroves, Erny said that a
\nnon-mangrove forest area can be established on the coast to
\nwithstand a tsunami.<\/p>\n
Baron Beach in Yogyakarta is a good example. Several species
\nof trees suitable for this purpose are, for example, cemara udang
\n(Casuarina sp), sengon, maleleuca and ketepeng. If these non-
\nmangrove forest areas are managed in a sustainable manner, people
\nliving on the coast can also boost their income and make use of
\nthe wood,\" Erny added.<\/p>\n
Aside from coastal forest areas, green belts must also be
\nestablished on coastal areas where mangroves are unsuitable.
\nThese green belts, which can comprise a variety of large, strong
\ntrees, are necessary for the southern coastal areas of Java as
\nthe area is unsuitable for mangroves.<\/p>\n
In their study titled Post-Tsunami Mitigation Investigation in
\nSouth Banyuwangi, East Java in 1995, Kris Budiono and colleagues
\nfrom the Center for Maritime Geology in Bandung, under the
\nauspices of the directorate general of geology and mineral
\nresources of the Ministry of Mining and Energy, noted that the
\nterritorial waters in the south of Java are the most active areas
\nin Indonesia due to insertion of the Indo-Australian plate under
\nthe Eurasian plate.<\/p>\n
In the last hundred years, there have been about 20
\nearthquakes of 6 to 7.7 magnitude on the Richter scale under the
\nsea.<\/p>\n
An example of a green belt that can withstand a tsunami can be
\nfound in the Air Hitam coastal area and the Pantai Panjang
\ntourist beach in Bengkulu, Sumatra.<\/p>\n
These areas sustained seven tsunamis between 1770 and 1958.
\nAccording to Nur Adi Kristanto, in a report titled Natural
\nDisaster Mitigation Investigation in Bengkulu and its
\nSurroundings (directorate general of geology and mineral
\nresources, Ministry of Mining and Energy, 1990), green belts are
\nmultifunctional as they can stop floating objects like wood and
\nvessels, reduce water speed, save drowning people and reduce
\nwinds that carry fine sand so that the sand can form dunes, which
\nis also another type of shield able to reduce the impact of a
\npowerful tsunami.<\/p>\n
It is now time for the Indonesian government and people to
\nlearn from the natural disaster that hit Aceh and North Sumatra.<\/p>\n
Natural shields must immediately be established in tsunami-
\nprone coastal areas. Erny is right when saying that to prevent a
\nnatural disaster we must make use of the forces of nature, such
\nas mangrove forests, coastal forests and green belts.<\/p>\n
Unless this measure is taken, we could suffer a repeat of the
\ntragedy in Aceh.<\/p>",
"url": "https:\/\/jawawa.id\/newsitem\/natural-shield-necessary-to-protect-ri-coastline-1447893297",
"image": ""
},
"sponsor": "Okusi Associates",
"sponsor_url": "https:\/\/okusiassociates.com"
}