Journal of Waterway, Port, Coastal, and Ocean Engineering

A numerical solution for the 2 + 1 (long-shore and onshore propagation directions and time) nonlinear shallow-water wave equations, without friction factors or artificial viscosity is presented. The models use a splitting method to generate two 1 + 1 propagation problems, one in the onshore and the other in long-shore direction. Both are solved in characteristic form using the method of characteristics. A shoreline algorithm is implemented, which is the generalization of the earlier 1 + 1 algorithm used in the code VTCS-2. The model is validated using large-scale laboratory data from solitary wave experiments attacking a conical island. The method is applied then to model the 1993 Okushiri, Japan, the 1994 Kuril Island, Russia, and the 1996 Chimbote, Peru tsunamis. It is found that the model can reproduce correctly overland flow and even extreme events such as the 30-m runup and the 20-m/s inundation velocities inferred during field surveys. The results suggest that bathymetric and topographic resolution of at least 150 m is necessary for adequate predictions, while at least 50 m resolution is needed to model extreme events, contrary to intuitive expectations that long waves would not interact with morphological features of such short scales.

The effects of sediment transport on the fluid velocities and turbulence in oscillatory flow were investigated with the aid of a laser Doppler anemometer (LDA). Measurements were made over flat beds in an oscillatory flow water tunnel with gradually increasing quantities of sediment. The sediment had a specific gravity of 1.137 and a median diameter of 4.0 mm. It was observed that the turbulence intensity at any given height above the initial bed level was less in flows with sediment motion than over a fixed bed provided the bed remained flat. The initial bed level is defined as the mean grain crest level if all sediment settles on the bed. The friction factor and energy dissipation factor at the initial bed level were also reduced by the addition of sediment provided the bed remained flat. On the other hand, the values of friction factor and energy dissipation factor at the bottom of the mobile layer of sediment were greater than the values for a fixed bed.

Innovative suction anchor piles have been used for permanent mooring of a process and accommodation barge at an oil and gas field developed by ELF Congo in the Gulf of Guinea. Twelve mooring lines, equipped with steel suction anchor piles, were successfully preinstalled at the site in July–August 1995, and the process barge was connected in early 1996 for the start of production. With a water depth ranging between 150 and 300 m, the Nkossa field is among the deepest ones offshore Western Africa to date, and the soils at the site consist of soft normally consolidated clays, representative of deep water sites. The anchoring system design is presented together with a description of the suction pile installation operations. The monitored performance of the suction piles during installation is evaluated, including the orientation and tilt at touchdown and the penetration rate during suction penetration. The installation behavior appeared to be easy and smooth, and the measured penetration resistances were in perfect agreement with the predictions, thus demonstrating the reliability of the design installation method.

A numerical model is presented that predicts the evolution of a directional spectral sea state over a varying bathymetry using superposition of results of a parabolic monochromatic wave model run for each initial frequency-direction component. The model predicts dissipation due to wave breaking using a statistical breaking model and has been tested with existing data for unidirectional random waves breaking over a plane beach. Experiments were also conducted for a series of random directional waves breaking over a circular shoal to test the model in a two-dimensional wave field. The model performs well in both cases, although directional effects are not included in the breaking dissipation formulation.

Delays in a waterway network are affected by tow arrival characteristics, service time distributions, lock characteristics, and control policies at locks. Previous studies have shown how interdependence among locks in a series complicates the delay estimation. Among control policies, “shortest processing time first” (SPF) yields lower delays and costs per barge than the generally used “first come, first served” (FCFS) policy. This report considers the interdependencies among locks in an integrated control algorithm for series of locks. The results show that an integrated control algorithm yields lower costs per barge for both FCFS and SPF control, with either equal or unequal directional flows. A modified SPF control that considers delays at adjacent locks (SPF&A) yields the lowest costs per barge among all control alternatives considered. The results show how the interdependence between locks decreases and delays increase as the distance between locks increases.

A new method of designing the bottom protection in harbors and waterways where maneuvering ships may cause damage due to propeller-generated water streams is presented. The method proposed differs from others because the suction forces that are generated at the interface between the structure and the subsoil are taken into account in the stability analysis. Such an approach allows for more economical designing of bottom protection as compared to other methods. Design formula, typical mechanical parameters, and examples of practical application are shown.