DOI: 10.17603/ds2-pe8w-x850
title: During-event Tsunami Observations at Crescent City Harbor
title: in Submergence of Floating Concrete Docks at Crescent City Harbor during the 2025 Kamchatka Tsunami

description: We investigated a rare tsunami-induced failure mode at Crescent City Harbor, CA: the transient, full submergence of large concrete floating dock modules without structural breakup. The mission focused on identifying the hydrodynamic mechanism(s)—particularly under-deck pressure deficits and blockage effects—that can overcome residual buoyancy and induce vertical instability under tsunami-driven currents.

The investigation combined during-event observations with rapid post-event reconnaissance. We assembled and time-synchronized harbor water-level records, georeferenced bathymetry/harbor geometry, as-built dock specifications, and high-frame-rate time-lapse video. Methods included: camera calibration and video-based kinematic tracking of freeboard loss and re-emergence; image-assisted current estimation and uncertainty bounds; simplified force-balance and Bernoulli/Venturi analyses for under-deck pressure; and consistency checks against harbor resonance timescales. All processing steps are scripted with documented inputs/outputs and metadata for reproducibility.

The dataset and analyses document a coherent submergence–resurfacing sequence consistent with negative hydrodynamic lift generated by accelerated, constricted flow beneath the dock. Despite large vertical excursions and joint misalignment upon resurfacing, global structural integrity was retained—implicating vertical stability, rather than strength, as the governing vulnerability. The mission yields traceable evidence linking basin-scale forcing, local current amplification, and float response, and distills testable thresholds for future modeling.

description: This project documents and analyzes a rare tsunami‐induced failure mode observed at Crescent City Harbor, CA, during the 29 July 2025 Kamchatka event: the temporary submergence (sinking without breakup) of large concrete floating dock modules. We assemble and time-synchronize heterogeneous data—harbor tide records, local bathymetry/geometry, as-built dock specifications, high-frame-rate time-lapse video, and derived kinematics/loads—to quantify the sequence of motions and the hydrodynamic conditions that led to negative lift under the dock (Venturi-type suction) and loss of freeboard. Reproducible scripts are included to regenerate all figures and calculations.

Reusability. The dataset and code can be reused to:
• Benchmark 1D/2D shallow-water and CFD models for current–structure interaction and under-deck pressure deficits.
• Develop or calibrate marina and small-craft infrastructure fragility functions under tsunami currents.
• Support performance-based design and retrofit criteria (e.g., underside geometries, reserve buoyancy, joint tolerances).

Uniqueness. Documented, instrument-constrained instances of floating docks fully submerging and re-emerging without structural fracture are exceedingly scarce. 

Audience. Primary users are coastal and harbor engineers, naval architects, and marina designers; researchers in tsunami hydrodynamics, fluid–structure interaction, and structural reliability; port authorities and emergency managers; and standards committees (e.g., ASCE/COPRI) seeking evidence-based guidance. The materials are suitable for graduate instruction in coastal engineering and for agencies evaluating marina resilience to tsunami currents.