Journal of Waterway, Port, Coastal, and Ocean Engineering

The runup of breaking solitary waves on a plane beach has been investigated. Experimental measurements demonstrate the effect of the impact of the jet from a plunging breaking solitary wave and the postbreaking bore formed on the resultant runup. An empirical method was developed based on energy conservation principles to provide an estimate of the runup of breaking solitary waves on a plane slope. Energy dissipation associated with wave breaking was estimated using the results from a numerical model developed by Li. The results from this highly simplified energy conservation model agree reasonably well with experiments, and this model appears to be useful in predicting breaking solitary wave runup on a plane beach.

This paper describes a methodology to assess the severity of a tsunami in progress based on real-time water-level data near the source. The inverse method, which uses tsunami signals in water-level data to infer seismic source parameters, is extended to predict the tsunami waveforms away from the source. This study focuses on the Alaska-Aleutian source region and its potential threat to Hawaii. The algorithm divides the source region into 41 subfaults based on previous analyses of major tsunamigenic earthquakes from 1938 to 1986. For unit slip of the subfaults, a linear long-wave model generates a database of synthetic mareograms at 13 water-level stations near the source and at six strategic locations in the Pacific. Regression of recorded tsunami signals using the mareograms provides the slip distribution at the source and the expected waveforms near Hawaii. A jackknife resampling scheme provides the confidence interval bounds of the predictions. The algorithm along with the database is tested and verified using numerically simulated and actual water-level data of past tsunami events.

A simple formula to calculate the settling velocity of natural sediment particles for grain sizes between 0.063 and 1 mm is presented. The formula has been derived from the previous work of Dietrich, and it predicts the dimensionless settling velocity $W_{*}$ as a function of a dimensionless fluid-sediment parameter $S_{*}\text{,}$ provided the sediment shape factor and roundness are known. In case no information on shape and roundness factors is available, this paper recommends using the formula with a shape factor of 0.7 and a roundness value of 3.5 for naturally worn particles. The formula is tested against several independent data sets, and its performance is compared to other existing simple settling velocity formulas. For fine sediments with nominal diameters $d_N$ between 0.063 and 0.25 mm, for which sediment suspension in natural conditions is most likely to occur, the proposed formula is shown to perform the best in terms of standard error of the estimation.

A real-time system for monitoring the dry weight contained in the hopper of a given dredge has been both designed and tested. Among the system’s most outstanding features, the following may be mentioned: it is of economical acquisition, can easily be set up in a brief period of time, and works independently from any other control systems incorporated into the dredge by the contractor. Moreover, its displacement is determined uninterruptedly. Ultrasound transducers are located on deck for the precise monitoring of cargo volume, and the data are collected through a personal computer and sent, via modem, to the client. The difference between automatic measuring and the standard manual system appeared to have a mean value of 5%. The content of solid matter in the hopper was 53%. Although this system has proven itself fully operative, certain protective measures have to be taken to shield those components exposed to rough maneuvering before the technical supervisors and controllers leave off.

The effects of mangrove trees on the flow field in a tidal estuary during high freshwater discharge events are investigated using a depth-averaged two-dimensional hydrodynamic model. The model is refined to include the effects of mangrove trees on flow resistance. The resistance is described by a set of two empirical equations depending on water depth and vegetative parameters. The vegetative parameters are investigated and tested using on-site samples of Kandelia plants. The model is calibrated and verified with experimental data measured in a physical model. The agreement between the measured and computed water surface elevation is good. The model is then applied to the entire tidal Tanshui River system, which includes mangrove swamps near the mouth of the Keelung River. The flow patterns and resistance distributions are investigated for several scenarios of high flow events. The results show that the refined model provides an ideal management tool for the mangrove swamps.

A procedure for predicting the significant height and period of wind waves generated in a uniform fetch in deep water is presented in the closed-form expressions based on Wilson’s formulas, together with relevant design diagrams. Although Wilson’s formulas are relatively unknown in the United States, they are quite reliable. The relationship between the nondimensional minimum duration and the nondimensional fetch length is empirically expressed in a power law, which enables the analyst to judge whether the wave growth is limited by the wind duration or the fetch length. The correlation between the significant wave height and period also indicates the period approximately proportional to the 2/3 power of the wave height.