Forensic Evaluation of Premature Breakwater Degradation Using Volumetric and Petrographic Evidence

Abstract

Breakwaters are essential for protecting coastlines from erosion, storm impacts, and related coastal hazards, yet their field performance depends not only on material durability but also on construction quality, geometric conformity, and the variability of the rock used. This study presents a forensic post-construction assessment of premature breakwater degradation in Selayar Regency, South Sulawesi, Indonesia, observed within less than one year after completion. Although the project satisfied Indonesian National Standards (SNI) for abrasion resistance and salt crystallization, field surveys revealed severe distress, including armour rock displacement, core layer fragmentation, crest lowering, and apparent material loss. Using an integrated volumetric and petrographic approach, the study combined document review, field measurements, and laboratory analyses to evaluate probable contributing factors associated with the observed degradation. Volumetric analysis identified a deviation of 733.05 m3 between the surveyed post-construction condition and the design geometry, indicating a substantial reduction in section geometry and structural mass. Petrographic analysis of the local limestone revealed contrasting lithological characteristics, ranging from highly porous and weakly cemented material to denser and better-cemented rock. The findings show that compliance with laboratory standards alone does not guarantee satisfactory field performance when geometric nonconformity and material heterogeneity are present. Because site-specific hydrodynamic loading and direct subgrade investigation data were unavailable, the results should be interpreted as a forensic identification of probable contributing factors rather than a complete attribution of all degradation mechanisms. The study highlights the importance of performance-oriented material evaluation and post-construction verification in marine rock structure construction.

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