Pemetaan Batimetri di Sungai Karang Mumus Kecamatan Samarinda Ilir Kota Samarinda

Abstract

The Karang Mumus River is a tributary of the Mahakam River flowing through Samarinda City, East Kalimantan, and plays an important role in the city's hydrological system as a waterway, a water source, and a floodway during the rainy season. Reliable information on the river's underwater topography is required to support navigation safety and flood-risk mitigation. This study aimed to map the topography and depth of the Karang Mumus riverbed, from Bridge 3 to the river mouth, and to present its longitudinal and cross-sectional profiles. Bathymetric sounding was carried out using a Garmin Map Sounder 585 Plus, arranged in five longitudinal survey lines at 10-m spacing and 66 cross-sectional lines at 25-m intervals, combined with a Comnav T300 geodetic GNSS receiver for riparian topographic measurement. Depth data were corrected against Mean Sea Level derived from 29 days of tidal observation using the Admiralty method, together with instantaneous tidal readings taken every 5 minutes during sounding, then processed in Microsoft Excel, AutoCAD Civil 3D, and ArcGIS. A total of 7,655 depth points were recorded over a survey area of 9.59 ha. The Mean Sea Level from the Admiralty analysis was 0.82 m, with a mixed, predominantly semidiurnal tidal type. Measured riverbed depths below Mean Sea Level ranged from 2.44 m at the shallowest reach (STA 0+150 - STA 0+175) to 32.92 m at the fish-auction port near the estuary, while the interpolated riverbed elevation model ranged from -2.15 m to -31.88 m. The resulting bathymetric, contour, longitudinal-section, and cross-section maps indicate the river remains navigable for small to medium vessels requiring a draft of 1.5-2 m, while highlighting shallow and narrow segments that warrant attention for safe navigation.