Wave Modeling of Infrastructure Modifications at Faleasao Harbor in American Samoa

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Effect of Hydrodynamics on Sediment Transport near a Coastal Inlet

River, Estuarine and Coastal Dynamic

Wave Response, Pago Pago Harbor, Island of Tutuila, Territory of American Samoa

Approved for public release; distribution is unlimited. The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. The findings of this report are not to be construed as an official Department of the Army position, unless so designated by other authorized documents. PRINTED ON RECYCLED PAPERERDC/CHL TR-02-2

Passaic River Basin Flood Protection Project Storm Surge Analysis

Source: https://erdc-library.erdc.dren.mil/jspui/The US Army Corps of Engineers, New York District, Passaic River Division (PRD) has been working on plans to reduce flooding in the Passaic River Basin since 1939, but none of those plans was authorized. Congress then authorized the Corps to conduct a new study of the basin for the state of New Jersey in the Water Resources Development Act of 1976. The Corps evaluated more than 150 plans, presented an array of plans to the state of New Jersey, and the state selected a dual-inlet water diversion tunnel system as the centerpiece of its comprehensive flood protection program for the basin. In November 1990, Congress authorized construction of the $1.2 billion Passaic River Flood Protection in the Water Resources Development Act of 1990; the project cost to the state is$310 million. The major elements of the project are two underground tunnels, a 20. l-milelong main tunnel about 40 ft in diameter and a 1.2-mile spur tunnel about 22 ft in diameter that convey central basin flood waters to an outlet in the vicinity of Kearny Point in Newark Bay. The proposed diversion tunnel and surface works are generally designed to ,protect against the 100-year flood event, during which it is anticipated that a flood volume equal to that of Newark Bay will be discharged over a two-day period. The Corps is studying the impact of discharging water from a diversion tunnel into Newark Bay and its tributaries, the Passaic and ~ackensack Rivers. While a diversion tunnel discharge itself would not cause significant flooding, it is the combination of a storm surge generated by hurricanes and northeasters coincident with the diversion tunnel operation that the Corps is evaluating. The main purpose of this study is to determine the stage-frequency curves for various locations and conditions throughout Newark Bay and the tidally influencedportion of the Passaic and Hackensack Rivers. These curves can be used to determine the heights of storms in the vicinity of Kearny Point. Another objective of this study is to examine the likelihood that a significant.diversion tunnel discharge could be coincident with a major storm surge, and to simulate such a combination, thereby determining the potential for additional flooding. During the 1970's and 19801s, a two-dimensional hurricane surge model was used for the Newark Bay/Passaic/Hackensack River system as boundary forcing for an interior Dynamic Estuary Model (DEM) to estimate flood frequencies. The current study builds on previous models and revalidates and uses a modified DEM to accurately simulate tidal elevations in the system using recent data on system bathyrnetry, river cross sections, topography, and historical hurricane, northeaster, and rain flow data through 1991, in combination with a refined grid. The revalidated DEM is a valuable engineering tool more accurately simulating tidal and river flows than previous studies. The coincidence analysis confirmed that large river flows are unlikely to coincide with large surges from New York Bight. Time history plots of several individual events show that there is a weak relationship between storm tides and river flows, and that the river flows lag the tides by several days; large storm tides with large Passaic River flows (lagged by 0-2 days) are extremely rare events. An increase in elevatiotis due to sea level rise has been accounted for in the stage-frequency distribution curves. The bootstrap method, a modification of the joint probability method, was used to generate stage-frequency distributions with 33 synthetic storms approximating the entire population of historical storms. Results of coincidence analysis show that large storm tides together with large river flows is an extremely unlikely combination, and they can be treated as essentially independent events. However, the analysis indicates that the likelihood of elevated river flows following storm tides (by 0-2 days) is quite strong. The effect of tunnel discharges to Newark Bay will have little effect (less than 0.1 foot) on tidal elevations in the lower Passaic River, Hackensack River, and Newark Bay where flood-prone areas are located. The inclusion of future project conditions, such as control levees in the vicinity of Kearny Point, changes the future unimproved stage-frequency distributions by less than 0.2 ft in the lower parts of the Passaic and Hackensack Rivers and in Newark Bay. However, the effect of tunnel diversion into Newark Bay will be to reduce river flooding in the upper tidal Passaic River by several feet

Application of the Green-Naghdi Theory of Fluid Sheets to Shallow-Water Wave Problems; Report 1: Model Development

Source: https://erdc-library.erdc.dren.mil/jspui/This report presents the mathematical formulation for the development of a numerical model that simulates wave transformation in shallow waters. The model is intended both for military and civil works projects involving propagation of time-dependent and nonlinear waves where existing models may either be inapplicable or use of simple analytic or numerical solutions is infeasible. The theory detailed in this report introduces a new-generation water wave model for shallow to moderate water depths where the seabed varies rapidly. The Green-Naghdi Level II theory, hereafter referred to simply as the GN theory, has been significantly modified in this research and a powerful, general-purpose numerical model, called GNWave, is developed for water wave problems. The theory and ensuing model incorporate some of the most important mathematical features of the water wave equations. These include non-approximating of the governing Euler's field equations and imposing the proper boundary conditions necessary for capturing the bulk physical characteristics of wave trains in the shallow-water regime. The GN approach, which is fundamentally different from the perturbation method based on developments in classical wave theory begun by Stokes and Boussinesq in the last century, can do this only because it does not introduce any simplifications of the velocity variation in the vertical direction across the fluid layers or sheets. In contrast to the Stokes and Boussinesq theories, the equations of motion in the GN theory are derived by enforcing exact kinematic and dynamic boundary conditions on the free surface and on the bottom, and by enforcing conservation of mass and of the 0th and 1st moments of momentum in the vertical direction. These conditions yield 11 coupled partial differential equations, which can be reduced to 3 complicated governing equations by elimination of many of the variables. In summary, the GN theory is different from the perturbation approach in that the free surface and bottom boundary conditions are met exactly, whereas the field equation is implicitly approximated. The result is a theory that can predict the shape and behavior of waves up to almost breaking conditions. The GN theory breaks down when the particle velocity at the crest equals the wave speed, the criterion for breaking in the exact theory. By developing the unrestricted Green-Naghdi theory of fluid sheets, this research presents a new wave theory consisting of a coupled, nonlinear set of partial differential equations and integrates these in time and space to simulate either regular or irregular real waves. The theory and model have been shown to reproduce with engineering accuracy the evolution of a wave of permanent form, from small amplitudes up to almost breaking conditions. The theory presented is for a nonlinear numerical wave tank in which the seabed topography profile can be arbitrary and very irregular, and up to 20 wave gages can be positioned at will inside the computational domain to obtain snapshots and profiles of wave records. The types of projects to which the theory can be applied are many, and include problems of both military and civil interest. The theory is purposely made to be versatile to permit decision makers, designers, and analysts to assess the various aspects of waves and wave-structure interaction problems arising in Army applications. One can evaluate, for instance, the effect of submerged obstacles during military landings on the train of waves approaching a beach or landing zone, or the reflection of waves and forces on sea walls or spillway hydraulic gates, and the time history of bottom-mounted pressure gage measurements for estimation of surface wave conditions in coastal design projects. The theory is particularly suited for the violent collision of waves with natural and man-made structures, and their impact on preventive and defensive hydraulic structures

User's Manual and Examples for GNWAVE

Source: https://erdc-library.erdc.dren.mil/jspui/This report describes the operation and use of a new numerical model, GNWave. This model was designed to simulate the evolution of a train of two-dimensional waves in waters of arbitrary bottom topography, varying from shallow water to waters of moderate depth. The program uses the Green-Naghdi theory of fluid sheets as its model, and integrates a set of coupled, nonlinear partial differential equations in time to perform the simulation of surface gravity waves. Report 1 in this series, entitled "Application of the Green-Naghdi theory of fluid sheets to shallow water wave problems," contains a detailed description of the mathematical basis of GNWave model. The model GNWave has been shown to reproduce with engineering accuracy the evolution of a wave of permanent form, from small amplitudes up to almost breaking conditions. The numerical model is portable with little or no changes to a wide variety of platforms, and has successfully been tested on high-end PC's and VAX and CRAY mainframe systems. The governing equations were programmed using Fortran as the language. The program consists of a main program and a number of modules to perform the calculations. A functional flow chart of individual routines involved in the computation is included herein. The main routine directs the sequence of the calculation, including the reading of the input and integration of the equations, and performs some post-processing. The main program is divided into two basic segments: an input portion where the specifications of the problem are read in and echoed to the computer screen, and an integration portion where the equations are integrated one time step at a time. Output is produced at pre-specified instants in the computation stages. The calculation involves four basic components: generation of waves at the ocean end of the wave tank, enforcement of an appropriate boundary condition at the shore end of the computational domain, solution of the two-point boundary value problem in space at a given instant in time, and integration of the equations in time. Each of these four components requires special techniques, which are discussed in this report to give the user an overview of the flow of information and a flavor for the computation that occurs during a simulation. To further assist the reader in understanding the implementation of the code, the algorithms used for wave generation, the treatment of beach-end boundary conditions, and the spatial and temporal integration of the governing equations are explained in the body of this report. Model input and output features are also presented, together with the procedure for using the program and the restart mode of operation of the model. Five example problems typically encountered in the military and civil works areas of the US Army Corps of Engineers are presented. These include collision of waves with a hydraulic spillway gate, waves transforming over an open-ended sloping beach, pseudo-spectral waves passing over a sand bar, random waves propagating through a dredged navigation channel, and regular waves shoaling on a landing beach of uniform slope. The first example problem tests the model's capability for a reflective boundary while the second problem checks the implementation of the transmissive or open type boundary condition. Simulation results for problems 3 and 4 are compared to illustrate the effects of a sand bar on the down-wave progressing in a channel. The last problem provides an opportunity to check the model simulation against physical model test data from a laboratory study conducted at the Danish Hydraulic Institute. The model has been shown to reproduce with engineering accuracy the evolution of regular and irregular wave trains up to the almost breaking condition