Environmental Engineering Reference
In-Depth Information
The engineering matrix is then
100100
100
§
·§
· §
·
¨
¸¨
¸ ¨
¸
1
EAB
010010
010
(5.87)
¨
¸¨
¸ ¨
¸
¨
¸¨
¸ ¨
¸
111011
101
©
¹©
¹ ©
¹
If the river sediment matrix is multiplied by the engineering matrix the river matrix will become the
channelized river matrix, i.e.
AE
B
(5.88)
The engineering matrix has to be studied and physically explained.
Review Questions
1. Answer the following questions
(a) What does “a 100-year flood” mean?
(b) For an open channel flow, the depth is 1 m and the average velocity is 1m/s, calculate the Reynolds
number and the Froude number. Is the flow laminar or turbulent? (
Ȟ
10
-6
m
2
/s) Is the flow supercritical
(Fr>1) or subcritical (Fr<1)?
(c) Explain the concepts of bed load, bed material load, suspended load, and wash load.
(d) State the order of development of bed forms following increasing flow intensity.
(e) What will happen if the bed configuration transforms from the lower regime into the upper regime?
(f) What are the main features of hyperconcentrated flow?
(g) What are the main river patterns?
(h) State the features of meandering and straight rivers, basic conditions for development of braided,
anabranching, wandering, and anastomosing rivers.
(i) At what conditions may a meandering river transform into a wandering river?
(j) What are the differences between sediment-carrying capacity and sediment-removing capacity of an
open channel flow?
(k) What is avulsion? Please give an example.
2. A flood occurs in a river channel of irregular shape. The in-situ measurements give values of the
average depth
, h
2 m, width,
B
500 m, the wet cross-sectional area,
A
1,000 m
2
, and the energy slope,
J
0.0001. The bank roughness is
n
w
0.025. Calculate
A
w ,
A
b
,
R
w
,
R
b
, and the bed roughness,
n
b
.
3. According to the minimum stream power theory, the morphology of fluvial rivers develops to reach
the minimum stream power. Thus, the following equation is obtained:
d
P
d
d
s
d
Q
J
§
·
(
J
sQ
)
Q
s
0
¨
© ¹
(a) You are designing an irrigation canal. How can you design the canal slope? Please explain with the
equation.
(b) d
P/
d
x
0
can also be explained as constant stream power. What is your opinion, minimum stream
power or constant stream power?
4. Please describe the phenomena of hyperconcentrated flows. What are the main differences between
hyperconcentrated flow and debris flow?
5. Draw water-sediment charts for a river and explain the implications of the chart.
6. For the Yangtze River the main sediment yield area is the drainage area between Panzhihua to Yichang,
from Yichang to Datong is the sediment transportation channel, and from Datong to the river mouth is
the estuary. The sediment matrix of the river is:
dd
x
x
d d
x
x
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