IDENTIFIKASI PERUBAHAN GARIS PANTAI SANUR DI SEKITAR GROIN BERBASIS NDWI DAN BAND THRESHOLDING
DOI:
https://doi.org/10.36733/jeco.v6i2.15085Keywords:
Abrasion, Coastline, Groin, Landsat, NDWIAbstract
Shoreline dynamics serve as an indicator of environmental changes in coastal areas, influenced by hydrodynamics, sediment transport, and coastal protection structures. Sanur Beach has experienced shoreline shifts resulting from the interplay of erosion, deposition, littoral drift dynamics, and the presence of groins. This study aims to identify changes in shoreline position and examine the shoreline's response to the presence of groins through multitemporal mapping based on satellite imagery. A descriptive research approach was employed, utilizing spatial analysis of Landsat imagery from the periods 1973–1982 and 2016–2026. Shoreline extraction from Landsat 8–9 imagery was performed using the Normalized Difference Water Index (NDWI), while Landsat 1–5 imagery was processed using a band-thresholding method based on near-infrared (NIR) reflectance. The extracted shorelines were compared spatially to identify shifts in position relative to the installation of groins. Visual interpretation indicates more pronounced shoreline changes during the 1973–1982 period, with several segments experiencing landward retreat. In the 2016–2026 period, changes appeared less significant across most segments, though the response varied by segment. These findings suggest an alteration in sediment distribution around the groin structures. Multitemporal mapping—utilizing NDWI and band-thresholding techniques serves as an effective preliminary approach for identifying shoreline changes and the morphological response of the coast to the presence of groins.
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