Geoscience Reference
In-Depth Information
constant through the reach and that the weighting factor in the storage function is
X
=
0.25. First,
estimate the value of the Muskingum parameter
K
from (a); then calculate the peak flow at the
downstream end of the reach.
7.12
Derive the diffusion equation (7.50) from (7.46), via (7.47).
7.13
Derive the expression for the design weighting factor,
X
d
, given by (7.59) from (7.56).
7.14
Multiple choice. Indicate which of the following statements are correct.
(a)
In general, the diffusion approach to describe flow in open channels can be considered
intermediate (in regard to the underlying assumptions) between the case of the moving
hydraulic jump (or bore) and that of the monoclinal rising wave.
Some of the underlying assumptions are:
(b)
that gravity effects are balanced completely by shear stress effects;
(c)
that the lateral inflow rate must be negligible;
(d)
that the channel is infinitely wide;
(e)
that the slope of the water surface relative to the channel bottom is negligible.
7.15
Multiple choice. Indicate which of the following statements are correct. The Muskingum flood
routing method makes use of storage function given by (7.15). This method:
(a)
works often well to predict the propagation of flood waves, involving slow and gradual
momentum changes;
(b)
has the advantage of not requiring any previous flood data, since the necessary parameters
can also be derived from information on channel roughness and channel geometry;
(c)
in its general form requires that the peak of the outflow,
Q
e
, from a channel reach occur at
the time when the inflow wave has the same rate of flow;
(d)
is rather restricted in its applicability, because it is based on the assumption that storage is
a function of the inflow and outflow with hysteresis;
(e)
can be applied to an ungated linear reservoir, provided the storage is made a function of
outflow only.
7.16
Multiple choice. Indicate which of the following statements are correct. During the passage of
a flood wave through a reservoir (whose outflow rate is controlled by a fixed weir), the peak of
the outflow hydrograph occurs (if both inflow,
Q
i
, and outflow hydrograph,
Q
e
, are plotted on the
same graph):
(a)
at the time of the inflection point of the inflow hydrograph;
(b)
at the time
t
=
K
, where
K
is a constant in
S
=
K
[
XQ
i
+
(1
−
x
)
Q
e
];
(c)
at the time where the slope of the outflow hydrograph goes from positive to negative;
(d)
at the time of the intersection with the inflow hydrograph;
(e)
at a time
K
units later than the peak of the inflow hydrograph.
7.17
Multiple choice. Indicate which of the following statements are correct. The motion of a flood
wave in a medium-size river:
(a)
is usually more like that of a bore (or moving hydraulic jump) than like that of a monoclinal
rising wave;
(b)
is always such, that the rate of flow is a unique, single-valued function of the water
depth.
