boundary hydraulics will be discussed in Chapters 3, 4, and 5. Chapter 2 is restricted to a
1-dimensional analysis of rigid boundary open channel flow, where velocity and acceleration
are large only in one direction and are so small as to be negligible in all other directions.
The three basic equations of flow: continuity, energy, and momentum are derived and used.
The characteristics of uniform or nonuniform, steady or unsteady, laminar or turbulent, and
tranquil or rapid (subcritical or supercritical) open channel flow are described, equations
derived and problems for highways in the river environment are solved. Example problems
are solved at the end of the chapter in both SI and English units of measurement.
1.7.2 Chapter 3 - Fundamentals of Alluvial Channel Flow
Most streams that a highway will cross or encroach upon are alluvial. That is, the rivers are
formed in cohesive or non-cohesive materials that have been, and can still be, transported
by the stream. The non-cohesive material generally consists of silt, sand, gravel, or cobbles,
or any combination of these sizes. Silt generally is not present in appreciable quantities in
streams having non-cohesive boundaries. Cohesive material consists of clays (sizes less
than 0.004 mm) forming a binder with silts and sand
Chapter 3 presents the fundamentals of alluvial channel flow. It covers properties of alluvial
material, methods of measuring these properties; describes flow in sandbed channels and
associated bed forms; presents methods for prediction of bed forms, and Manning's n for
sandbed and other natural streams; describes how bed-form changes affect highways in the
river environment; presents equations, tables and figures for determining the beginning of
motion of non-cohesive sediments; and describes the methods used for the physical
measurement and calculation of sediment discharge. These fundamentals of alluvial
channel flow are used in later chapters to develop design considerations for highway
crossings and encroachments in river environments. Example problems are solved at the
end of the chapter in both SI and English units of measurement.
1.7.3 Chapter 4 - Sediment Transport
The quantity and quality of the sediments that a stream can transport is an important
consideration for highways in the river environment. Scour at a bridge or culvert is a sediment
transport process. Streambed erosion and movement is the result of sediment transport. The
amount of sediment transported or deposited in a stream under a given set of conditions is the
result of the interaction of two groups of variables. In the first group are those variables that
determine the quantity and quality of the sediment brought down to that section of the stream
(bed and bank material). In the second group are the variables that determine the capacity of
the stream to transport that sediment.
Chapter 4 presents the terms that describe sediment transport, discusses the methods and
fluid forces that move sediment, derives and explains the basic equations, and presents
equations and computer models that other practitioners have developed. Example problems to
determine the quantity and quality of sediment transport are solved at the end of the chapter in
SI and English units of measurement.
1.18
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