Civil Engineering Reference
In-Depth Information
Base-of-rail
High water level for
Q
Area,
A
, required for
Q
Elevation
A
b
1
b
4
B
b
2
b
3
A
Plan
H
1
y
u
y
d
y
Section
A
-
A
FIGURE 3.3
River crossing profile with obstructions at
Q
.
similar to the flow past a constriction but with more openings (Figure 3.3).The degree
of contraction is usually less for obstructions than constrictions. Published values of
C
c
for various obstruction geometries are available in the literature on open channel
hydraulics (Yarnell, 1934; Chow, 1959).
The flow about an obstruction consisting of bridge piers was extensively
investigated (Nagler, 1918) and Equation 3.9, which is similar in form to Equation 3.5,
