Sand Dunes, a natural wonder in Parangtritis, Yogyakarta

According to the Indonesian Dictionary, a dune is a small sand hill on the beach. Meanwhile, according to Shuckin, sand dunes are accumulations of sand formed by wind, both in coastal and desert areas. So, a sand dune is an accumulation of sand that is lifted by wind power (eolin) to an area on land and form a certain appearance. The process of moving material in the form of sand and fine grains occurs over a long period of time and occurs continuously. This process is known as deflation. Parangtritis Sand Dunes is a unique phenomenon, because the process involves the landscape from upstream to downstream. Parangtritis Sand Dunes are formed from sand material from the activities of Mount Merapi in the upstream area, which is carried by rivers that originate at Mount Merapi, which then settles in the estuary and is later carried by currents and waves to the beach (Sungkowo et al, 2014).

The main uniqueness of the sand dunes in Parangtritis is the type of sand dune formation. On the sand dunes in Parangtritis, there are barchan or crescent type sand dunes. This type of sand dune is rare because it only forms in a few places, such as in the Philippines and Vietnam (Putra, 2016). The shape of this barchan-type sand dune is characterized by the appearance of 2 horns, and closely resembles the shape of a crescent moon. The height of this sand dune can reach 5 to 15 meters. The barchan-type dune is located in a relatively flat area with strong and stable wind speeds. This type of sand dune is very easy to move, which really depends on the size of the dune. The smaller the size of the pile, the faster it will move.

Figure 1. Barchan-type dune in Parangtritis

Source: pgsp.big.go.id

The sand dunes formed in Parangtritis are not only admired for their beauty, but also for their ecological functions. Sand dunes have the ability to prevent coastal disasters. Some coastal disasters that can be prevented by the presence of sand dunes include:

1. Tectonic earthquake vibration damper; The sand dune texture has the ability to absorb earthquakes, as happened in the 2006 Yogyakarta earthquake, where buildings in the sand dune area only suffered moderate to light damage.

2. Damping tsunami waves; The morphological type of Sand Dunes area, where the shape stretches for two kilometers with a height of up to 15 meters serves to dampen the impact of the Tsunami waves

3. Recharge Areas; Through the process of infiltration and percolation in the sand dune, the rainwater that is accommodated in the sand dune will become fresh groundwater. With this advantage, the availability of fresh groundwater on the coast will be maintained and prevent seawater intrusion

4. Prevents abrasion and erosion from high sand dunes

To support the ecological function of the sand dunes, the sand dunes need to be protected by the government by creating a legal protection. Therefore, the Government affirms the protection of sand dunes through various legal grounds, one of which is in Presidential Regulation no. 51 of 2016 about Coastal Boundaries, Article 4, it is stated that one of the objectives of determining coastal boundaries is for the preservation of ecosystem functions and all resources in coastal areas and small islands, including sand dune ecosystems. Under the regulation, there is also a Decree of the Head of the Geological Agency of Yogyakarta which stipulates that the barkhan sand dunes and hot springs in Parangtritis Village are a joint geological nature reserve area (Putra, 2016). In addition to the legal protection, on the basis of land rights, the Parangtritis sand dune area also includes in the Greatness Area of ​​Dalem Gumuk Pasir Barkhan Parangtritis. This means that the entire Parangtritis sand dune area belongs to the Sultanate of Yogyakarta (Sultan Ground) (Wulan et al, 2016)

Despite all the regulations and rights that protect the Parangtritis Sand Dunes, the threat of damage from Parangtritis Sand Dunes is unavoidable. The increasing economic activity of residents around Parangtritis ultimately requires the use of the existing space around Parangtritis which also changes the coastal area of ​​Parangtritis (Marfai et al, 2011). Based on research on aerial photo data in the Parangtritis Sand Dunes from 1972 to 2015, land use in the sand dunes may increase from year to year which is marked by a decrease in the Parangtritis sand dune area (Fakhrudin et al, 2010; Wulan et al, 2015). In Figure 2, it can be seen that in 1972 the area of ​​the sand dune was 396 hectares, and decreased to 239 hectares. Until 2015, the area of ​​the sand dune was only 33 hectares.

Figure 2. Sand Dunes area from 1972 to 2015

Source: Fakhrudin et al,2010; Wulan et al, 2015

There are several causes for the reduced area of ​​the Parangtritis sand dune. One of them is the planting of pine vegetation which was planted in 1975 (Fakhrudin et al, 2010). This planting disrupts the wind tunnel area, which is one of the energy forming sand dunes. Another obstacle is sandy land farming and illegal sand mining. The development of residential areas also contributes to inhibiting the formation of sand dunes

Various ways have been done to save the Parangtritis sand dune, among others, by coordinating between stakeholders in the form of restoration. This restoration began in 2015, with the inauguration of the Gumuk Pasir Core Zone. The restoration then continued with the relocation of residential areas around the Gumuk Pasir Core Zone. This transfer process certainly did not go smoothly and was rejected by some residents. Finally, after deliberation, all residents in the Gumuk Pasir Parangtritis area wanted to be moved to the selected area. Of course, this restoration step is a big step in an effort to save the Parangtritis sand dunes from extinction

BIBLIOGRAPHY

Fakhruddin M, Poniman, Aris., H. Malikusworo. 2010. Dinamika Pemanfaatan Lahan Bentang Alam Gumuk Pasir Pantai Parangtritis, Kabupaten Bantul. Jurnal Ilmial Geomatika Vol 16 No. 2: (3-12)

Marfai, M. A., Protomoarmojo, Nursakti Adhi., Hidayatullah, Tufik., Nirwansyah, Anang Widhi., Gomareuzzaman, Muammar. 2011. Model Kerentanan Wilayah Pesisir Berdasarkan Perubahan Garis Pantai dan Banjir Pasang (Studi Kasus: Wilayah Pesisir Pekalongan). Cetakan Pertama: November 2011. RedCarpet Studio. Yogyakarta. 80 hlm.

Peraturan Presiden Republik Indonesia Nomor 51 Tahun 2016 Tentang Batas Sempadan Pantai

Putra, Mega Dharma. 2016. Nilai Ekonomi Imbuhan Airtanah Dari Air Hujan Pada Kawasan Bentang Alam Gumuk Pasir Parangtritis. UGM Yogyakarta

Shuckin, dikutip dari buku I Gede Piata, 2009, Pengantar Ilmu Pariwisata, Andi Offset, Yogyakarta,

hlm.203.

Sungkowo, A., E. Muryani, dan F.A. Astuti. 2014. Penilaian Relatif Ekosistem Gumuk Pasir Sebagai Kawasan Konservasi atau Pertambangan di Pantai Selatan. Makalah diprensentasikan pada Seminar Nasional Kebumian – IX Fakultas Teknologi Mineral UPN Veteran Yogyakarta, Yogyakarta 4-5 Desember 2014

Sunarto. 2014. Geomorfologi dan Kontribusinya dalam Pelestarian Pesisir Bergumuk Pasir Aeolian dari Ancaman Bencana Agrogenik dan Urbanogenik. Pidato Pengukuhan Jabatan Guru Besar Fakultas Geografi Universitas Gadjah Mada. Yogyakarta: Fakultas Geografi Universitas Gadjah Mada.

Wulan, T.R., Ambarwulan, W., Putra, A.S., Maulana, M., Maulia, N., Putra, M.D.,Wahyuningsih, D.S., Ibrahim, F., Raharjo, T. 2016. Uji Akurasi Data UAV (Unmanned Aerial Vehicle) di Kawasan Pantai Pelangi, Parangtritis, Kretek, Bantul. Prosiding Seminar Nasional Kelautan 2016 Universitas Trunojoyo Madura ISBN: 978-602-19131-4-7