LAJU SEDIMENTASI DI PERAIRAN BREBES, JAWA TENGAH MENGGUNAKAN METODE ISOTOP 210Pb - Wisnu Arya Gemilang; Gunardi Kusumah; Ulung Jantama Wisha; Ali Arman (Pusat Penelitian dan Pengembangan Geologi Kelautan, 2017)
Beberapa upaya mitigasi terhadap bencana erosi yang terjadi di kecamatan Brebes telah dilakukan dengan penanaman mangrove, pemasangan hybrid engineering, alat pemecah ombak, namun dari keseluruhan upaya tersebut masih dianggap belum menjadi solusi terbaik mengurangi dampak bencana erosi pantai. Penelitian ini bertujuan untuk mengetahui tingkat rata-rata kecepatan sedimentasi berdasarkan umur absolut sedimen dasar laut yang dianggap mewakili daerah penyelidikan. Penentuan umur absolut sedimen berdasarkan aktifitas kandungan isotop alam 210Pb pada sedimen. Hasil perhitungan laju sedimentasi tersebut dikorelasikan dengan data debit sungai dan kondisi hidro-oseanografi yang berperan dalam sistem sedimentasi. Berdasarkan profil unsupported 210Pb pada lokasi IST-01 (Muara Pemali) dan IST-02 (Muara Nipon) rata-rata laju sedimentasinya berturut-turut 0,224 cm/tahun dan 0,211 cm/tahun, debit Sungai Pemali sebesar 14,4-48,1 m3/s, kecepatan arus pada stasiun IST-01 berkisar antara 0,001-0,1 m/s dan kecepatan arus pada stasiun IST-02 berkisar antara 0,001-0,08 m/s. Kondisi hidro-oseanografi daerah penelitian yang fluktuatif memberikan pengaruh besar terhadap proses sedimentasi. Besarnya debit sungai memiliki korelasi terhadap peningkatan besarnya nilai laju sedimentasi di Muara Pemali dan Muara Nippon. Hasil penelitian tersebut dapat dijadikan bahan rekomendasi upaya mitigasi bencana erosi di kecamatan BrebesKata Kunci: Sedimentasi, Pesisir Brebes, Hidrodinamika arus, Isotop Unsupported 210Pb Several efforts to mitigate the erosion event which occurred in Brebes sub district have been done by mangrove cultivation, hybrid engineering, and breakwater as well. Nevertheless, all those efforts did not work right away to solve the erosion problem and deteriorate its impact. This study has aim to determine the absolute sediment dating, which represents the study area. We decided the absolute sediment dating based on natural isotop activity 210Pb contained on sediment. Sedimentation rate calculation result was correlated with the river discharge and hydro-oceanography conditions in the sediment area systems. Based on unsupported 210Pb profile, at the station IST-01 (Pemali estuary) and IST-2 (Nipon estuary), the averages of sedimentation rate are 0.22 cm/year and 0.211 cm/year respectively. The discharge of Pemali River has ranged 14.4-48.1 m3/s. The current speed at the point IST-01 has ranged 0.001-0.1 m/s and at the station IST-02 has ranged 0.001-0.08 m/s. The hydro-oceanography condition which is volatile has a big impact on the process of sedimentation. The enhancing of river discharge has a correlation with the sedimentation rate enhancement in Pemali and Nippon estuary. The result of this study could be a basis of erosion mitigation effort in Brebes sub district.Keywords: Sedimentation, Brebes, Hydrodunamics of surface current, Isotop Unsupported 210Pb