Journal of Waterway, Port, Coastal, and Ocean Engineering

In this study a method for making long‐range forecasts of freezeup dates in rivers is developed. The method requires the initial water temperature at an upstream station, the long‐range air temperature forecast, the predicted mean flow velocity in the river reach, and water temperature response parameters. The water temperature response parameters can be either estimated from the surface heat exchange coefficient and the average flow depth or determined empirically from recorded air and water temperature data. The method is applied to the St. Lawrence River between Kingston, Ontario, and Massena, New York, and is shown to be capable of forecasting the freeze‐up data.

Linear diffraction theory for large floating offshore structures of arbitrary shape and subjected to a regular uni‐directional wave train is extended to obtain the forces and responses in multi‐directional random waves with a specified directional wave spectrum. The transfer functions, spectra and crossspectra of the components of forces and motions are first obtained. These are used in turn to obtain the probabilistic properties of the corresponding force and response components and their horizontal resultants. In particular, the expected values of the single largest maxima of these forces and responses in a specified duration are obtained.

Grouping of high waves in a long‐traveled swell recorded at a shallow water location is examined. The swell, with most of the energy concentrated within a narrow band of frequencies (0.040–0.075 Hz), is assumed to have originated in the southern Indian Ocean. The longest run of high waves identified contained 6 waves for $H>H_s$ and 16 waves for $H>H\text{.}$ The observed probabilities of runlengths are in agreement with the theory of Kimura. Very high correlation between successive wave heights (up to 0.79) and significant correlation up to 5 waves apart, which is higher than all earlier reports, are observed. It is found that the correlation coefficient between successive wave heights $r_{\mathrm{HH}}$ (1) is a better parameter to define the length of runs of wave heights than the spectral peakedness parameter, $Q_p\text{.}$ The high values of runlengths observed raise doubts regarding the concept of a decrease of runlengths in shallow water, which has lately been confirmed by Thompson and Seelig.

Dimensionless presentations of wave diffraction through a narrow breakwater gap have been computed from the analytical solution of Morse and Rubenstein. Particular attention is given to narrow gaps, typical of smaller harbors, and to the wave field near the gap, where available details are approximate and most sparse. These solutions are compared with frequently‐used approximate solutions from superposition of partial Sommerfeld solutions for a semi‐infinite breakwater. The superposition approximation is extended to angled incidence for wide breakwater gaps and generally to non‐aligned breakwaters.

Estimating barge tow resistance in shallow water by Howe's formula can lead to an error in estimating the tow speed of large tows. While not enough published data is available to update Howe's formula, it is worthwhile to have an accurate formula for typical barge tows. The present note addresses this deficiency by presenting a comparison of the actual barge tow resistance given by estimates made using Howe's formula and the results from extrapolating the deep water resistance estimate using Schlicting's method. A two resistance augment is obtained and then introduced to Howe's equation for V > 6.0 mph to obtain accurate estimates for a 5 × 3 barge tow in waterdepth h = 16 ft (4.88 m).

An explicit solution for wave number and wave speed is derived. The method of solution is to expand the linear wave dispersion relation in Taylor series in the neighborhoods of deep and shallow water limits. The two series are matched at the inflection point of the dispersion function, where the shoaling wave height is a minimum value. Numerical comparisons indicate that the present solution is computationally efficient and has an error of less than 0.05%. Two applications are made to solve problems, involving nearshore spectral analysis and refraction of ocean waves.