practical problems along with existing data. A careful analysis of data requirements would
make it possible to more efficiently utilize funds to collect data in the future. The basic type of
information that is required includes: water discharge hydrograph, sediment discharge
hydrograph, the characteristics of the sediments being transported by streams, the
characteristics of the channels in which the water and sediment are transported, and the
characteristics of watersheds and how they deliver water and sediment to the stream systems.
Environmental data is also needed so that proper assessment can be made of the impact of
river development upon the environment and vice versa. The problem of data requirements at
river crossings is of sufficient importance that it is treated in greater detail in Chapter 8.
1.6 FUTURE TECHNICAL TRENDS
When considering the future, it is essential to recognize the present state of knowledge
pertaining to river hydraulics and then identify inadequacies in existing theories and our
understanding of the physical processes involved, and encourage further research to help
correct these deficits of knowledge. In order to correct such deficits there is a need to take a
careful look at existing data pertaining to rivers, future data requirements, research needs,
training programs and methods of developing staff that can apply this knowledge to the
solution of practical problems.
Advances have been made in developing computational software to establish hydraulic
variables for scour computations, including 1- and 2-dimensional, steady and unsteady
models. Most, if not all, of the commonly used scour prediction equations have been
incorporated into these models. However, applications methodologies are required to
facilitate the use of more appropriate hydraulic variables that can be obtained from more
sophisticated computer models. World wide web sites providing hydraulic models applicable
to scour computations include:
+ www.fhwa.dot.gov/bridge/hydsoft.htm
+ www.hec.usace.army.mil/software/index.htm
1.6.1 Adequacy of Current Knowledge
The basic principles of fluid mechanics involving application of continuity, momentum and
energy concepts are well known and can be effectively applied to a wide variety of river
problems. Considerable work has been done on the hydraulics of rigid boundary open
channels and excellent results can be expected if the principles are applied properly. The
steady-state sediment transport of nearly uniform sizes of sediment in alluvial channels is well
understood. There is good understanding of stable channel theory in non-cohesive materials
of all sizes. The theory is adequate to enable us to design stable systems in the existing bed
and bank material or, if necessary, designs can be made for appropriate types of stabilization
treatments so that canals and rivers behave in a stable manner. There have been extensive
studies of the fall velocity of non-cohesive sediments in static fluids to provide knowledge about
the interaction between the particle and fluid so essential to the development of sediment
transport theories.
1.15
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