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Comparative Hydraulic Performance of Conceptual Breakwater Armor Geometries under Changing Sea States: Effects of Sea-Level Rise and Irregular Waves
Mohammad Taghipour1 , Reza Dezvareh *1 , Nosrat A. Fallah1
1- Faculty of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran
Abstract:   (17 Views)
Climate-change-driven sea-level rise reduces breakwater freeboard and can permit larger wave groups to reach the structure before depth-induced breaking occurs, thereby increasing run-up and overtopping. This study evaluates the hydraulic resilience of two conceptual concrete armor geometries: a symmetric unit (Type A1; 1:1 aspect ratio) and an elongated unit (Type A2; 1:2 aspect ratio). Six rubble-mound breakwater configurations (B1-B6), combining slopes of 1:1.5 and 1:2.0 with regular or irregular placement, were represented as fixed geometries in FLOW-3D. The numerical model used three-dimensional Reynolds-averaged Navier-Stokes equations, an RNG k-ε closure, volume-of-fluid free-surface tracking, FAVOR geometry representation, and a porous-core formulation. Irregular incident waves were generated from a normalized JONSWAP spectrum with significant wave heights of 1.6 and 1.8 m, a peak period of 6.0 s, and still-water depths of 3.3, 3.8, and 4.3 m. Model performance was checked against published overtopping data. A local-maximum crest-exceedance analysis and empirical crest-exceedance response curves were used to quantify the hydraulic response across the modeled water levels; this hydraulic limit state does not represent physical armor displacement or breakage. Across the six configurations, the +1.0 m water-level scenario increased exceedance probability by 21-57 percentage points relative to baseline. When averaged across the two modeled significant wave heights, B3 (irregular A2, slope 1:1.5) increased from 35% to 92%, whereas B1 (regular A1, slope 1:1.5) increased from 15% to 38%. The response is consistent with greater flow-path tortuosity in the symmetric layer and preferential channeling in irregular elongated arrangements. Screening-level Hudson mass corrections indicate substantially larger adaptation demands for A2. Because the armor units were fixed and the probabilities were derived from finite numerical records at three water levels, the results should be interpreted as comparative hydraulic screening metrics rather than annual failure probabilities or structural service-life predictions.
Keywords: Rubble-mound breakwater, Concrete armor unit, Sea-level rise, JONSWAP spectrum, Wave overtopping
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Highlights
  • Six breakwater configurations compared under JONSWAP waves and SLR scenarios.
  • Symmetric A1 armor showed lower crest-exceedance than elongated A2 armor.
  • At +1.0 m SLR, crest-exceedance rose by 21–57 percentage points.
  • Irregular A2 on 1:1.5 slope increased from 35% to 92% exceedance.
  • Hudson screening suggests much larger compensatory mass for elongated A2.

 
Type of Study: Research Paper | Subject: Offshore Structure
Received: 2026/06/25 | Accepted: 2026/09/26
Audio file of the article abstract [MP3 4065 KB]  (3 Download)
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