Journal of Waterway, Port, Coastal, and Ocean Engineering

Bays as a predominant physical feature of the coastlines of the world have been recognized for some 30 years. Their plan form has received attention for over 20 years. The shape equated to a logarithmic spiral has received much attention, but is shown in this paper to be not uniformly applicable. Bays can exist in an unstable form (implying that with cessation of littoral drift they can erode back to a shape known as static equilibrium, the knowledge of whose characteristics can permit determination of their stability), or indentation, reached under conditions of no sediment supply.

Crenulate‐shaped bays are ubiquitous, with a large spectrum of sizes on coasts, enclosed seas, lakes, and rivers. They exist where waves arrive persistently from an oblique direction to the general coast. They thus indicate to man nature's way of maintaining beaches that are in dynamic or static equilibrium. This phenomenon can be utilized to retain beaches in locations where erosion was previously encountered. Such a process has been termed “headland control.” It is applicable to any shapes of coastline, be it straight, bayed, or convex. The headlands can be designed to minimize the effect of storm waves on them. It must be accepted that such waves will still remove the beach berm almost annually to form an offshore bar that affords protection to facilities landward of it. Their direction of arrival dictates the volume of material so demanded, which can vary around the periphery of a bay.

The delivery and yield of coarse sediment (sand and gravel) in the Santa Clara River have been studied through mathematical modeling of spatial and temporal variations of sediment characteristics for time‐dependent fluvial processresponse. The interactive effects on sediment yield due to sand and gravel mining, a major grade‐control structure, and the dams in the drainage basin are integrated in the mathematical modeling. The simulation results are useful for identifying river reaches subject to potential erosion and deposition. They are also useful for obtaining mean annual yields at different river locations. The mean annual yield computed for the most seaward cross section is representative of the mean annual delivery to the coast. The study illustrates how scour and fill of the channel bed are accompanied by significant changes in channel width, which may contribute significantly to sediment storage. Thus, sediment yield can be quantified by an erodible‐boundary model, as opposed to an erodible‐bed model.

The reason for submitting one more scenario to this spectacular failure is that it may prevent a similar occurrence. It is suggested that failure was due to bed subsidence or liquefaction, so causing the supporting rubble material to slide, together with armour units, in a sudden downward movement. Breakage of dolosse at depth rather than in the upper region fits this explanation well, as does the bulging at the base being less than the cross‐sectional area removed at the top of the face. The progressive scouring from the northern end toward the southern head matches the prior subsidence and lack of damage at these extremities, respectively. The bed failure was caused by its erosion from reflection of waves arriving obliquely to the straight N‐S segment of the breakwater, which was damaged over almost its complete length simultaneously. Similar scour to that hindcast for Sines has been recorded or predicted for other large breakwaters. Perhaps frequent hydrographic surveys, with planned remedial measures implemented quickly, may prevent a future calamity, but the reasons for collapse must be understand for these to be effective.

Fluid‐mud seabeds have significant effects on the attenuation of water waves that propagate over them. In this paper an analytical solution is presented for solitary waves propagating over fluid‐mud seabeds. In the theoretical analysis three boundary layers are introduced to satisfy the continuity conditions of motion. The first approximation is derived for the velocities in the irrotational cores and the boundary layers, as weir as the dissipation rates of wave heights. The theoretical attenuation coefficients are compared favorably with the laboratory experiment results.

Hydraulic model tests were conducted on two different natural harbors to study the influence of diffraction and reflection of irregular waves compared to regular waves. Two types of reflective walls within one harbor were also tested. Irregular wave trains with different peak frequencies and groupiness factors were generated. These tests have shown that within the limits of the frequency band of the spectral energy density, irregular wave diffraction‐reflection coefficients show less variability and appear to give better information than do the ones obtained from regular wave tests. Outside the frequency range containing most of the energy of the incident wave train, high values of the transfer function were observed in the lower and upper frequency range. However, their energy content was relatively small, and the long wave energy attached to wave grouping could not be attributed to harbor resonance. In the high frequency range, the presence of noise is attributed to the high transfer function estimates.

Local approximations are recommended as a tool for the analysis of natural water waves. The particular class of local approximations described is based on local fitting of a sine curve, which leads naturally to the definition of locally defined frequencies. As a specific application, two methods are outlined for estimating surface elevations of large (nonlinear) waves from subsurface pressures. One of the methods is simple enough to be condensed into a single formula that expresses the surface elevation in terms of three pressure readings. Yet, its accuracy is better than that of the traditional spectral transfer method. Guidelines are presented for the use of the methods in connection with real (noisy) data.

A study was conducted between 1978 and 1984 in a 72 mile-long stretch of the Ohio River to detect the influence of construction of the Smithland Locks and Dam on bank instability. Changes in bank appearance were noted during four inspections made before dam construction and pool raise, and during two inspections made after pool raise. The navigation dam raised river pool levels as much as 22 feet. During inspections, the entire extent of the stream affected by the navigation dam was evaluated. Banks were classified (high-eroded, low-eroded, vegetated, etc.). Correlations of erosion classification with magnitude of pool raise, planform location, and other factors were attempted. This work extended previous site-specific erosion evaluations and studies in other reaches of river. This was the first before dam-after dam study of bank erosion, of this kind, ever published. It was found that raising the navigation pool in 1981, had no effect on riverbank appearance and apparent erosion between 1978 and 1984.

Examination of more than 700 miles (1,120 km) of Ohio River banks between 1977 and 1986 indicated that erosion intensity and extent decreased between 1983 and 1986. Detailed examination of 106 sites in the study area confirmed the bank survey results. During 1983-1986, commercial river traffic increased more than 35%. Many sites became more stable during this traffic increase, while other nearby sites with similar bank soils and plan-form locations remained unchanged. These circumstances indicated that waves from in-channel traffic had no significant impact on bank erosion and instability on this portion of the Ohio River.

This note describes a simplified method for estimating the flow rate and flow velocity through the gaps of permeable offshore segmented breakwaters caused by wave overtopping. The method incorporates previous two-dimensional laboratory tests and resulting empirical equations for estimating ponding (setup) behind the breakwater. Factors that can be investigated using this method are the influence of breakwater freeboard, wave height and period, breakwater length and spacing, number of breakwaters, distance offshore, water depth at the breakwater, and shore attachment on the flow rate. Other wave effects on hydraulics, such as diffraction, refraction, reflection, and wave-current interactions, have not been considered. The method can be extended to other similar situations via laboratory testing and/or analytical results on flow through and over breakwaters.