Tanker-Induced Surges/Breaking Waves in Harbors

Cline’s Point Marina, located in Port Aransas, TX, has been experiencing detrimental wave conditions near the marina’s entrance and within the marina itself during the passage of deep-draft ship traffic. The wave activity is primarily generated outside the breakwater-protected marina entrance by pressure field effects from large, laden outbound vessels in Corpus Christi Ship Channel (CCSC). Deep-draft vessel-induced surge analysis was performed to evaluate water level fluctuations and surge-induced current velocities inside the marina generated by passing vessels using the vessel hydrodynamics longwave unsteady (VH-LU) modeling system. It was observed from the modeling of existing structural conditions that the pressure field effects change significantly at higher passing speeds (e.g., 10 knots). At higher speeds, along with the long-period (150–250 s) surge wave component, additional short-period (high-frequency, 10–20 s) wave components are observed in the water level time series, that manifest themselves as breaking waves as observed in site photos. Various marina entrance breakwater improvement alternatives were developed and analyzed for reducing the penetration of both the long-period water level oscillations and shorter-period breaking waves into the marina. The VH-LU system was found to accurately simulate both the long-period water level fluctuations and the breaking (bore) waves in the marina. Analysis of water level time histories throughout the marina using fast Fourier transform routines was performed to quantify the long and short-period ship wave energy with maps of each produced to compare performance of alternatives. It was determined that restoration of the breakwater or other structural modification of the marina entrance along with selective deepening within the marina will help in reducing the penetration of these waves into the marina or the impacts of these waves after they enter the marina.