Journal of Waterway, Port, Coastal, and Ocean Engineering

Guidelines in the form of a flexible step‐by‐step procedure are presented for the management of contaminated dredged material. The guidelines are intended to assist decision‐makers in their planning for dredging operations that could pose problems if not given special consideration. The procedure follows preliminary assessment of the contamination of sediment that is to be dredged. The procedure assists in the determination of appropriate and compatible means for dredging, transport, treatment, and disposal of dredged material. It combines means into viable alternatives which are then evaluated on the basis of several criteria: reliability, technical effectiveness, environmental impact, cost, regulatory requirements, public acceptance, safety, and practicality.

A procedure that was developed to assist decision makers plan for proper management of contaminated dredged material is illustrated with the use of a case study. Decisions regarding dredging operations of contaminated dredged material are outlined for a project in Commencement Bay, Tacoma, Washington. Preliminary screening of potential disposal sites is described and using criteria developed for the case study. In addition, appropriate means for dredging, transport, treatment, and disposal are determined and combined into alternatives. Viable alternatives are evaluated using criteria established as part of the overall decision‐making procedure. Final selection of an alternative is presented in terms of two objectives: cost minimization and maximization of a composite qualitative criterion which incorporates several characteristics of each alternative.

A model for estimating wave forces on dolosse is presented. It is shown that unreinforced units are susceptible to structural failure for hydraulically stable wave conditions. Reinforcing armor units will greatly enhance their structural capacity and longevity. A simple model for dolos motion is developed based on wave forces. Determination of incipient armor unit motion as a function of wave and structure conditions provides an alternative to Hudson's formula. Dolos motion is only slightly dependent on depth. For breaking wave conditions, motion is highly dependent on wave period and is largest at intermediate periods.

The results of an investigation of the effect of lee‐wake on scour below pipelines in currents are reviewed. The subject is investigated both experimentally and numerically. The experiments show that the scour downstream of the pipe is apparently governed by the action of an organized wake flow, which is an agglomeration of large‐scale vortices which are shed from the pipe and steadily convected downstream. The experimental results lead to a clear understanding of the effect of lee‐wake on the scour phenomenon. In the numerical part of the study the so‐called cloud‐in‐cell method is employed to predict the flow. The results appear to reveal almost all the features of the organized wake flow shown by the experiments. The theoretical calculations demonstrate that the time average bed shear stress is not a suitable parameter to work with in mathematical‐model studies of lee‐wake scour.

The propagation of water waves in a direction perpendicular to the longitudinal axis of a rectangular submarine trench is studied for a density‐stratified fluid in the trench. The theoretical and experimental investigation has focused on the excitation of internal waves within the trench. The study shows that, when the frequency of the propagating surface waves corresponds to the natural frequency of internal waves in the trench, the amplitude of the interfacial waves becomes large compared to the amplitude of the surface waves. The effects of the internal waves on the surface waves are not measurable; the surface waves are sensitive more to changes in depth than to the effects of density stratification. The results of a linear inviscid theory are compared to experiments and show good agreement with various aspects of the observed trench motion.

A spectral wave model based on a numerical solution of the radiative transfer equation is used to create a synthetic data base on wave conditions within hurricanes. The results indicate that both the velocity of forward movement and maximum wind velocity within the storm play an important role in determining both the magnitude of the waves generated and the spatial distribution of these waves. An equivalent fetch for hurricane wave generation that is a function of these two parameters is proposed. This concept, combined with the standard JONSWAP fetch‐limited growth relationships, provides a simple means for estimating wave conditions within hurricanes.

A modification of the linear wave theory of the interaction between wind‐induced waves and an infinite vertical wall is presented. As the free surface fluctuates with time, a point fixed in space in the vicinity of the mean water level is not submerged at all times but emerges from the water in some phases of the wavy motion. The modification consists of taking into account this effect, which is referred to in this paper as the emergence effect. Its influence is essential when determining the stochastical characteristics of pressures and forces on the vertical wall. Numerical results for the mean value and variance of the dynamic pressure and force induced by wind waves are obtained and presented graphically. Comparisons are made with the case in which the free surface fluctuation phenomenon is ignored. Inclusion of the free surface fluctuation phenomenon appreciably changes the mean value and variance of the pressure and force relative to the unmodified theory. The difference is most pronounced at points near the mean water level.