Journal of Waterway, Port, Coastal, and Ocean Engineering

Design of detached breakwaters for shore protection is difficult because the response of the shoreline to these structures is governed by at least 14 geometric‐, wave‐, and sediment‐related variables. Numerical models of shoreline change have the potential of incorporating these variables to predict the time evolution of the beach plan shape; however, wave transmission at breakwaters has been a major process absent from such models. In this paper, a pragmatic method of calculating the breaking‐wave height and angle under combined transmission, diffraction, refraction, and shoaling is tested to predict shoreline change measured at Lorain, Ohio, the site of a three‐segment transmissive breakwater system. The model successfully simulated observed shoreline change at the site that occurred over three time periods ranging from one to five years. Model sensitivity to changes in key parameters and simulations of alternative shore‐protection designs to the Lorain project are also described.

The Reversing Falls separate the Saint John River almost completely from its tidal estuary: only a small portion of the tidal energy present in the Bay of Fundy tide manages to propagate into it. Harmonic analyses reveal that 28‐ and 15‐day oscillations, not the semidiurnal tide, dominate the fluctuations in the water levels upstream although the latter is unusually strong in the estuary. The long‐period oscillations are created by the periodic retention of some of the fresh water during intervals of perigean or spring tides, the cause of the phenomenon being obvious during intervals of constant discharge. Wide fluctuations in runoff created by the spring freshet mask the interaction temporarily. Since the range of downstream tides still contributes to the retention of fresh water, the coincidence of a peak in runoff with extreme tidal ranges could create unusually high levels upstream.

A kinematic approach is taken to examine analytically the Euler‐Lagrange transformation and the basic behavior of fluid parcel trajectories associated with a monochromatic oscillatory current field having progressive wave characteristics. This study examines (1) The dependency of the Lagrangian motions on the initial release conditions; and (2) the distinction between the Eulerian and Lagrangian time scales and its implications on the residual Lagrangian flow field. While the instantaneous trajectory of a labeled parcel depends strongly on the initial conditions, the appropriate period in the Lagrangian framework $T_{\mathrm{Lag}}$ and the residual Lagrangian drift over such a period are independent of the initial conditions. Because $T_{\mathrm{lag}}$ and the Eulerian time scale $T_{\mathrm{eu}}\text{,}$ defined as the period of the oscillatory Eulerian current, may be quite different, the residual Lagrangian drift over a complete $T_{\mathrm{eu}}$ may show strong dependency with the initial release conditions. It was also found that while the Eulerian current is monochromatic, the Lagrangian trajectory exhibits multiple harmonics, with components at both higher and lower frequencies relative to the fundamental frequency.

Most post‐1970 theoretical studies of longshore current velocity extend the radiation stress theory of Longuet‐Higgins. Of the two larger sets of laboratory data (1949, 1963) available to test theories, Longuet‐Higgins used the 1963 data and considered but did not use the 1949 data. Most post‐1970 theories reverse these judgments and rely on the 1949 data. Such theories must be reevaluated. The 1949 data are 37 experiments, of which 22 were run on slopes steeper than all but the steepest natural foreshores; 12 of 37 published breaker angles exceed the generator angle; breaker depth‐to‐height ratios for the steep laboratory slopes were computed (not measured) using empirical curves from flat field slopes; and dimensionless velocities have a unique distribution. Breaker angle is the most sensitive variable determining longshore current velocity. Properly defined breaker angles require duplicate measurements along the test beach. The test velocity selected to compare with theory must account for the nonuniformity of most laboratory currents. An erroneous column heading in a 1967 listing of the 1963 data misled some subsequent investigators.

Three hindeast wave‐data sets for deep water off the central California coast region are compared using design wave‐height estimates. The three independent hindeast techniques compared are from the Army Corps of Engineer's Wave Information Studies (WIS), the Navy's spectral ocean wave model (SOWM), and the Pacific Weather Analysis (PWA) model. Sampling, plotting, and distribution fitting of the three data sets are treated such that all three wave‐height estimates may be compared equally. The three hindeast data sets are compared and evaluated using the 50‐ and 100‐year significant wave‐height estimates and the distribution and sampling parameters. The comparison reveals that SOWM appears to overestimate the extremal wave statistics. For the region under study, the WIS and PWA models predict similar 50‐ and 100‐year return‐period design wave heights.

Revised criteria is presented for wave shoaling after breaking on a plane beach and for resulting wave forces on a wall landward of the still-water line. Existing criteria is based on the assumption that the wave height above still water will remain constant between the point of wave breaking and the shoreline. A review of experiments carried out by several different researchers shows a marked reduction in wave height following breaking; and the assumption used in existing criteria will overestimate wave heights by a factor of four and wave forces by a factor of 16. New criteria is presented that more accurately predicts the height of a broken wave. Revised equations are given for calculating resulting wave forces.