Journal of Waterway, Port, Coastal, and Ocean Engineering

Design-flood levels with associated exceedance probabilities are usually determined for coastal flood protection projects. Rising sea level introduces another design feature that needs to be combined with the design-flood level. However, most sea-level projections do not have exceedance probabilities that can be used in conjunction with the design flood to obtain total flood levels. This paper shows how to combine design-flood levels with sea-level rise projections that have exceedance probabilities, such as those of the Intergovernmental Panel for Climate Change, to obtain total elevations at desired exceedance probabilities over particular intervals.

The current study proposes prediction formulas both for random wave runup and mean overtopping discharge at seawalls constructed on land or in very shallow water. Although several existing formulas for runup and overtopping use the incident wave characteristics at the toes of seawalls, this study adopts the equivalent deepwater wave characteristics and an imaginary seawall slope for easy application of the formulas, especially in relation to seawalls constructed on land. The prediction formulas for overtopping use the predicted runup values. For the wave runup prediction formulas two sets of experimental data are used; i.e., a new set of data and the data obtained in a previous study. For the wave overtopping prediction formulas, the experimental data measured in a previous study are used. Comparisons with measurements show good performances of both new prediction methods.

Profiles of exceptionally large waves before a vertical breakwater were obtained by using a gauge array. These profiles were compared with the profiles obtained using the quasi-determinism (QD) theory. The experiment performed in the field confirmed the QD theory for a wave field that is strongly nonhomogeneous in space.

A methodology is developed to extract and process shoreline data, the interface between land and water, identified from imagery. Initially, image pixels containing water (water points) and pixel locations of the land/water interface (edge points) are extracted from an image using either a supervised, threshold approach or a newly developed, automated texture-based analysis. Both are described and demonstrated. Subsequently applied is a procedure for processing these edge and water point locations to obtain oriented and ordered shoreline coordinates. The described methodology has several advantages: (1) shoreline processing is independent of imagery source and resolution, that is, specification of search directions based on image resolution or desired shoreline resolution is unnecessary and (2) a need for additional postprocessing of remote-sensed data or extracted-edge data are obviated, that is, edge data need not be of high quality or vectorized. Details of the entire methodology, including algorithms for water and edge point extraction from imagery and specifics of the processing applied to obtain an ordered, oriented shoreline, are presented. Execution of the complete shoreline extraction algorithm is demonstrated independently by application to sections of the East Pearl River, Mississippi, and the Kootenai River, Idaho. A quantitative performance measure of the ability of the algorithm to produce realistic-ordered, oriented shoreline coordinates from a set of edge and water point data extracted from imagery results in RMS errors of 1 m or less or two times the ground sample distance of the imagery.

Long-term changes in the sand balance of a river-estuary system can strongly affect navigation and ecosystems. Here, we examine two sand budget components in the lower Columbia tidal river, fluvial supply and human removal. Rating curves were used to estimate daily sand input between 1900 and 2010. Publications, interviews, and data analyses were used to evaluate sand removal by dredging and mining. Comparison between sand input and removal indicates that a sand deficit has existed for $>50$ of the last 85 years. Since 1962, the deficit has averaged $4.62\hspace{0.17em}(\pm 1.74)\times {10}^6\hspace{0.17em}{\text{ts-yr}}^{-1}$. Although historic sand transport to the ocean cannot be estimated, it is now small. Several factors contribute to the sand deficit: dredging, sand mining, flow regulation by dams, and climate change. The sand deficit documented here has likely contributed to the lower water levels in the tidal river observed in recent decades, which decreases habitat availability during high flows and channel depths during low-flow periods.

Several empirical formulas have been proposed to predict the near-bed conditions for sediment transport in steady channel flows; however, few are extendable to oscillatory flows. This study presents a method for evaluation of the reference concentration and the entrainment rate near the undisturbed bed under oscillatory sheet-flow conditions. A new expression of the erosion depth in terms of the Shields parameter is adopted in order to describe the conservation of sediment mass more accurately. Both the exponential law and the power law are used to represent the instantaneous sediment concentration profile. The newly obtained formulas explicitly express the reference concentration and the entrainment rate in terms of the near-bed flow conditions and the sediment properties. The maximum value of the reference concentration obtained has a similar trend as given by the classical formulas. However, the variation of the reference concentration within a period of the oscillatory flow shows better agreement with the measured data than the classical formulas. In addition, the newly obtained formulas are found to have an evident advantage over the classical ones because they can reasonably interpret the sediment concentration as the flow reverses. The new formulas on the total vertical flux of sediment are also shown to reasonably agree with the measured data. It is demonstrated that the entrainment functions obtained under steady flow conditions, particularly those over a starved bed, are not directly applicable to oscillatory sheet-flow occasions.

Laboratory experiments have been carried out to investigate the scour around single piles and twin-pile groups subject to oscillatory flows. The Keulegan-Carpenter number, which is proportional to the ratio between the maximum excursion of water particles and the pile diameter, ranges from 3 to 110 in the experiments. To verify the experimental setup, the scour around a tall monopile was first studied, and the results were found to agree well with the previous research. The effect of the pile height and the influence of the twin-pile layout on the scour have been subsequently investigated. It was found that the scour became independent of the pile height once the pile was four times higher than the diameter. An empirical expression was constructed to describe the exponential variation of the scour depth with the pile height. The individual piles in a twin-pile group were found to behave independently when the separation was three times greater than the pile diameter. The relationships between the scour depths around the twin-pile groups and the group configuration were established graphically.

In this paper, wave scattering by a vertical cylinder with a scour pit governed by the modified mild-slope equation (MMSE) is studied analytically. The scour pit around the cylinder is assumed to be axi-symmetric and idealized with its radial profile being a power function. This assumption permits transformation of the two-dimensional MMSE into an ordinary differential equation (ODE) in the radial direction through the technique of variable separation. By employing a newly derived explicit form of the resultant ODE of the MMSE in the scour pit region, an exact solution to the MMSE is constructed in terms of a Fourier-cosine series and Taylor series. To validate this new analytic solution to the MMSE, a comparison among the present solution, analytic solution to the long wave equation, and analytic solution to the Helmholtz equation is made and a good agreement is obtained. It is found that the present MMSE model is valid for a maximum bottom slope of approximately 0.927. Based on the present solution to the MMSE, the effect of dimensions of the scour pit, including both depth and width, on wave run-up around the cylinder is investigated. Finally, the influence of the wavelength of incident waves from shallow to deep water on wave run-up around the cylinder is also investigated.

Vessels arriving at a port wait for an available berth at the quay to load/unload. The ability to provide a berthing space for a vessel without delay is a major managerial concern. Thus, there is an optimal resource-allocation problem, in which the resource is the length of the quay allocated dynamically over the vessels according to an arrival process. Unfortunately, quay length cannot be changed arbitrarily because of the construction and operating costs, which are increasing functions of the quay length. This paper’s concern is the determination of the optimal quay length, and this problem is formulated using a variant of the stochastic knapsack problem. This method is primarily intended to estimate the length of a single quay. After introducing the mathematical formulation for the model, it is applied to a number of case studies built based on the real data obtained for several ports. Next, a sensitivity analysis of the model is presented with a wide range of arrival and service parameters drawn from real-life data. The paper concludes with a practical approach to estimating the quay lengths roughly.