Kuantifikasi dan Karakterisasi Acoustic Backscattering Dasar Perairan di Sekitar Pulau Pramuka, Teluk Jakarta

Abstract

Dasar perairan memiliki peranan yang sangat penting yaitu sebagai habitat bagi bermacam-macam makhluk hidup yang kehidupannya berasosiasi dengan lingkungan perairan. Hal ini dapat dilihat dari seberapa besarnya dasar perairan tersebut memberikan kontribusi bagi pertumbuhan dan perkembangan makhluk hidup yang berada di dasar perairan. Perkembangan metode baru untuk mendapatkan informasi mengenai tipe dasar, sedimen dasar dan vegetasi bawah air dengan menggunakan echosounder dan pengolahan data secara digital sudah mulai berkembang.

Seabed has a very important role as the habitat for various living creatures, and critical part of aquatic environment. Nowadays, new methods to obtain information on bottom types, sediment characteristics and underwater vegetation in shallow water by using echosounder has flourished. In this paper, normal incident of acoustic waves were used to determine values of bottom backscattering strength (volume backscattering strength (Sv), surface backscattering strength (SS) and echo level (EL)). Sediment properties (acoustic impedance, bulk density, porosity, sound speed and sediment composition) were used to explain the acoustic measurement results. Data collection was carried out in Seribu Islands, Jakarta using SIMRAD EY 60 scientific echosounder systems with operating frequency 120 kHz. The results show that the average value of volume backscattering strength (Sv) for sand is -13,23 dB and silty sand is -21,15 dB. The average value of surface backscattering strength (SS) for sand is -23,30 dB and silty sand is -31,22 dB. The average value of echo level (EL) for sand is 177,94 ± 8,61 dB and silty sand is 167,23 ± 6,07 dB (Source Level (SL) for split beam transducer ES 120-7C series is 214 dB). These acoustics values were then used as input for PCA analysis to cluster seabed characteristics. It’s shown that the acoustic technique can be used to identify and classify sediments and map sediment provinces. Key words: sediment