The use of computers and the development of computer programs have greatly helped the
hydraulic engineer to solve problems on highway crossings and encroachments. The level of
effort required to apply these models to bridge and hydraulic structure design has been greatly
reduced with the availability of graphical user's interfaces. These interfaces are used for model
development, troubleshooting, output presentation, and review.
The one-dimensional
WSPRO (FHWA) or HEC-RAS (Corps of Engineers) computer programs are extremely useful
to determine the water surface elevation and the velocity of the flow in a river at a highway
crossing. Both the Corps' and HEC-RAS (Version 3x) and UNET models are particularly useful
in unsteady flow problems. FHWA's BRI-STARS program can be used to determine flow of
water and sediment through a bridge crossing. FHWA's FESWMS and the Corps of Engineers
RMA-2V 2-dimensional models provide water surface elevation and local velocities in two
dimensions for unsteady flows for complex problems such as tidal flows. The Corps of
Engineers HEC 1 and related HEC HMS programs are of particular importance in routing water
from an upstream gaging station downstream to a bridge, taking into account any increase or
decrease in flow that might occur in between the station and the bridge.
Thus, available concepts and theories, which can be applied to the behavior of rivers, are
extensive. However, in many instances only empirical relationships have been developed and
these are pertinent to specific problems only. Consequently, a more basic theoretical
understanding of flow in the river systems needs to be developed.
With respect to many aspects of river mechanics, it can be concluded that knowledge is
available to cope with the majority of river problems. On the other hand, the number of
individuals who are cognizant of existing theory and can apply it successfully to the solution of
river problems is limited. Particularly, the number of individuals involved in the actual solution
of applied river mechanics problems is very small. There is a specific reason for this deficit of
trained personnel. Undergraduate engineering educators in the universities in the United
States, and in the world for that matter, devote only a small amount of time to teaching
hydrology, river mechanics, channel stabilization, fluvial geomorphology, and related problems.
It is not possible to obtain adequate training in these important topics except at the graduate
level, and only a limited number of universities and institutions offer the required training in
these subject areas. There is great need for adequately trained and experienced practitioners
to cope with river problems.
1.6.2 Research Needs
As knowledge of river hydraulics is reviewed, it becomes quite obvious that many things are
not adequately known. Some research needs are particularly urgent and promise a rather
quick return. Stabilization of rivers and bank stability of river systems needs further
consideration. Also, the study of bed forms generated by the interaction between the water
and sediment in the river systems deserves further study. The types of bed forms have been
identified, but theories pertaining to their development are inadequate. Simple terms have
been used to describe the characteristics of alluvial material of both cohesive and
non-cohesive types; a comprehensive look at the characteristics of materials is warranted.
Other important research problems include the fluid mechanics of the motion of particles,
secondary currents, two-dimensional velocity distributions, fall velocity of particles in turbulent
flow and the application of remote sensing and geographic information system techniques to
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