1
Introduction
In performing its mission to maintain navigable waterways along U.S. coasts,
the U.S. Army Corps of Engineers (USACE) regularly applies analytical and
numerical models to estimate the total longshore sediment transport (LST) rate.
Accurate prediction of LST rate is essential when predicting beach response in
the vicinity of coastal structures, designing beach nourishment projects, and
estimating sedimentation rates in navigation channels. For design applications
with adequate field measurements, the commonly used CERC formula (Shore
Protection Manual 1984) can be calibrated and applied to estimate total LST rates
with reasonable confidence (+/- 50 percent error). However, for design
applications without calibration data, the CERC formula provides only order-of-
magnitude accuracy. Very little information and guidance are available for
defining the cross-shore distribution of LST.
To address deficiencies in existing methods for calculating LST, the Large-
scale Sediment Transport Facility (LSTF) has been constructed at the U.S. Army
Engineer Research and Development Center's (ERDC) Coastal and Hydraulics
Laboratory (CHL). The intent for the facility is to reproduce certain surf zone
processes found on a long, straight, natural beach in a finite-length wave basin.
Ongoing work in the LSTF is part of a research program to improve USACE's
capability to predict local and total LST rates and to evaluate errors associated
with these predictions. The LSTF simulates nearshore hydrodynamic and
sediment transport processes at a relatively large geometric scale, including
situations where considerable sand is mobilized and transported in suspension.
Chapter 2 provides an overview of the LSTF, including a brief description of
its major components. Chapters 3 and 4 provide much more detailed information
about the design of both the longshore current recirculation and sediment
trapping and handling systems. Chapter 5 discusses the procedures for molding
beach morphology to the prescribed profile shape. Chapter 6 describes the
automated system for controlling experiments and the data acquisition and
analysis package that is used to process measured data. Chapter 7 describes
operational procedures used for controlling the wave generators and pumps that
force the longshore current distribution. Chapter 8 describes the calibration,
measurement, and analysis of various types of data that are acquired during
experiments: wave, current, sediment concentration, beach topography, and
quantities of sand that accumulate in traps located at the downdrift boundary of
the facility. Chapter 9 describes the critical iterative process for establishing the
proper longshore current and summarizes results from regular and irregular wave
longshore current experiments performed on a planar concrete beach. The
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Chapter 1
Introduction
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