Rivers and Flooding

Question 1

Discharge is measured by multiplying the _____ by the ______.

Answer 1

average water velocity: area of the water in the channel

Question 2

How can the potential for flooding be reduced without reducing discharge?

Answer 2

increase velocity by

• increase slope (S)
• increase channel efficiency (R)
• decrease sinuosity
• reduce roughness coefficient (n)

Question 3

One way to increase the slope of a stream channel is to

Answer 3

decrease sinuosity

Question 4

Lateral migration of a meandering stream results in _______.

Answer 4

decrease in slope

increase in sinuosity

Question 5

The geological process of ______ happens at point bars.

Answer 5

Deposition

Question 6

_____ are evidence for lateral migration.

Answer 6

meander scrolls

Question 7

process that occurs at cutbank side of a stream

Answer 7

erosion

Question 8

How does urbanization affect flooding?

Answer 8

decreases lag time while increasing peak discharge

Question 9

The probability of a 50 year flood occuring next years is?

Answer 9

2%

Question 10

What is the probability of a 100 year flood occuring the next year?

Answer 10

1%

Question 11

rainfall is gentle favors _______.

Answer 11

infiltration

Question 12

soil is porous and sandy favors ______.

Answer 12

Infiltration

Question 13

ground is nearly saturated favors ______.

Answer 13

runoff

Question 14

surface lacks vegetation and is barren favors ______.

Answer 14

runoff

Question 15

What is the plot of discharge or stage and time called?

Answer 15

hydrograph

Question 16

The boundary that separates one drainage basin from another is known as:

Answer 16

drainage divide

Question 17

In hydrograph the maximum discharge corresponds to ______.

Answer 17

flood peak

Question 18

The formation of a meander cutoff results in a(n) _____ in sinuosity

Answer 18

decrease

Question 19

The layers of fluids in an oil trap is controlled by ______.

Answer 19

density

Question 20

cap rocks have ____ permeability and _____ porosity

Answer 20

low, low

Question 21

Greenhouse effect is caused by the ______.

Answer 21

absorption and rerdiation of outgoing, long wavelength, radiation by greenhouse gases (CO2)

Question 22

A ____ channel has a smaller hydraulic radius than a _____ channel.

Answer 22

wide and shallow : semicircular

Question 23

In Manning’s equation, n measures ______.

Answer 23

the resistance to flow at the bottom of a channel

Question 24

In Manning’s equation R is _____.

Answer 24

a measure of the efficiency of a channel cross section

Question 25

Slope is calculated by dividing _____ by \_\_\_\_\_\_.

Answer 25

vertical drop of channel's end points : length of channel

Question 26

Lateral migration of a meandering stream results in a(n) ____ in sinuosity.

Answer 26

increase

Question 27

feature that results from meander cutoff

Answer 27

oxbow lake

Question 28

feature that results from lateral migration of the stream

Answer 28

meander scrolls

Question 29

How do you calculate hydraulic radius (R)?

Answer 29

R=A/P A = area of water in channel P= wetted perimeter of channel

Question 30

Three ways to increase velocity of water in a channel.

Answer 30

1. decrease resistance to flow (n) 2. increase channel efficiency (R) 3. increase slope (S)

Question 31

wide, shallow channel has ____ R.

Answer 31

low

Question 32

A semicircular channel has _____ R.

Answer 32

high

Question 33

Sinuosity is _____ divided by \_\_\_\_\_\_.

Answer 33

channel distance **/** linear distance

Question 34

urbanization ______ lag time.

Answer 34

decreases

Question 35

urbanization _____ discharge.

Answer 35

increases

Question 36

what equation gives you averge water velocity in a channel?

Answer 36

Manning's equation

Question 37

Slope is ______ divided by \_\_\_\_\_\_.

Answer 37

vertical drop of the channel's end points, length of channel

Question 38

exceedance probability is

Answer 38

the probability (p) of an event of a particular magnitude being equaled or exceeded any given year.

Question 39

What is reccurence interval

Answer 39

average number of years between events of similar or greater magnitude