Flooding - Flood Hazards

Question 1

this refers to when a normally dry areas of the land become inundated

Answer 1

flooding

Question 2

what is the most common way that a flood can occur?

Answer 2

when excessive amounts of overland flow cause an increase in discharge, river channel can no longer hold all of the flow of water and will eventually overflow its banks

Question 3

scientists use _________ and __________ to compare floods in a quantitative manner

Answer 3

stream discharge and height

Question 4

is the height at which a river begins to overflow ots banks

Answer 4

flood stage

Question 5

how is discharge computed?

Answer 5

multiplying cross sectional area of a river to its average velocity

Question 6

t or f: flood stage gets higher as you go further from banks

Answer 6

t

Question 7

the severity of flood is quantified by measuring wither __________ or _____

Answer 7

stream discharge or stage

Question 8

refers to any level where stream has gone over its banks

Answer 8

flood stage

Question 9

t or f: there is an inverse relationship between discharge and height

Answer 9

F (direct)

Question 10

why are floods difficult to predict?

Answer 10

because they are largely dependent on specific weather events that have a high degree of natural variability

Question 11

t or f: flood frequency does not tell us when a flood of a certain magnitude will occur, but rather the probability or chance of it happening

Answer 11

t

Question 12

represents the frequency of a particular discharge value can be expected to repeat itself

Answer 12

recurrence interval

Question 13

what does a 100-year recurrence interval mean?

Answer 13

on average, 100 years should pass before that same discharge will occur again

Question 14

t or f: a 100-year flood could take more than 100 years to repeat, but could just as easily reoccur in less than 100 years

Answer 14

T

Question 15

t or f: low discharge events occur frequently more than high discharge events

Answer 15

t

Question 16

the inverse or reciprocal of recurrence interval (1/RI)

Answer 16

percent probability

Question 17

a 10-year flood has a percent probability of?

Answer 17

10%

Question 18

what does a 10% probability of a flood means?

Answer 18

10 percent probability that a flood will take place in any given year

Question 19

this tell us how often we can expect floods of a certain size

Answer 19

recurrence interval

Question 20

indicate the chances of occurring of flood of certain size

Answer 20

percent probabilities

Question 21

what is the difference between recurrence interval and percent probabilities?

Answer 21

recurrence interval tell us how often we can expect a flood of certain discharge can occur, whereas percent probabilities can tell us their chances of occurring

Question 22

the reliability of recurrence interval is dependent on the ___________

Answer 22

availability of historical discharge records

Question 23

formula for recurrence interval

Answer 23

RI = (N+1)/M

where:
N = number of values in the record
M = rank of the discharge

Question 24

what is the unit for recurrence interval?

Answer 24

year

Question 25

the potential for flooding in a given area naturally increases as the ________ and _________ of rainfall increases

Answer 25

intensity and duration

Question 26

rainfall events might range from _______ to ______

Answer 26

light to torrential rains

Question 27

t or f: light rains are steady and may last for few days while torrential rains only last for a few minutes to several hours

Answer 27

t

Question 28

another important factor associated with rainfall is the ____________

Answer 28

size of the area over which the rain falls

Question 29

relatively small storms that tend to keep moving and may generate intense rains, but flooding is more localized

Answer 29

isolated thunderstorm

Question 30

storms that move inland from the ocean and can drop tremendous amounts of water over large areas, thereby producing widespread flooding

Answer 30

large regional storms

Question 31

a generic term used by meteorologists to describe a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has closed, low-level circulation

Answer 31

tropical cyclone

Question 32

The weakest tropical cyclones are called

Answer 32

tropical depression

Question 33

when is a tropical cyclone considered a hurricane or typhoon?

Answer 33

when its wind reaches 74 miles per hour or higher

Question 34

where is the term "hurricane" used?

Answer 34

Atlantic ocean, Eastern Pacific ocean

Question 35

where is the term "typhoon" used?

Answer 35

Northwest Pacific

Question 36

where is the term "tropical cyclone" used?

Answer 36

South Pacific and Indian Ocean

Question 37

what are the natural factors that affect flooding?

Answer 37

1. nature of precipitation events 2. ground conditions 3. vegetation cover

Question 38

the ability of ground to absorb water

Answer 38

infiltration capacity

Question 39

explain how infiltration capacity plays a critical role in flooding

Answer 39

water that is unable to infiltrate will br eventually forced move as overland flow

Question 40

the actual rate at which at which water can infiltrate is determined by the _______, _______, and ________

Answer 40

slope of the surface, type of ground material, and moisture content of material

Question 41

t or f: as slope becomes progressively steeper, infiltration capacity decreases

Answer 41

t

Question 42

t or f: gravel and sand-rich soils have higher infiltration capacity than clay soils

Answer 42

t

Question 43

t or f: infiltration capacity decreases as soil becomes more saturated

Answer 43

t

Question 44

how can vegetation cover affect flooding?

Answer 44

vegetation intercepts and stores a certain fraction of rain, thereby preventing it from reaching the land surface and moving as overland flow vegetation enhances absorptive capacity, decreasing runoff and overland flow

Question 45

the potential for flooding depends on:

Answer 45

1. how much and for how long precipitation rate exceeds the infiltration rate 2. size of the area of which the rain falls 3. vegetation density

Question 46

floods that have short duration with relatively high peak discharge

Answer 46

flashfloods

Question 47

t or f: flashfloods generally affect only localized areas

Answer 47

t

Question 48

t or f: flashfloods are dangerous due to their sudden nature

Answer 48

t

Question 49

why are flashfloods dangerous?

Answer 49

they are sudden in nature, which means people have less time to evacuate

Question 50

flashfloods are also referred to as

Answer 50

upstream floods

Question 51

t or f: flashflooding can occur in downstream areas

Answer 51

t

Question 52

where in downstream areas can flash floods occur?

Answer 52

along small tributaries

Question 53

t or : flashfloods can also occur from sudden failure of dams

Answer 53

t

Question 54

can be defined as one where the river leaves its channel farther down in its drainage basin, flowing out into floodplain and inundating large areas of the valley floor

Answer 54

downstream flood

Question 55

what does downstream flood inundate?

Answer 55

valley floors

Question 56

what causes downstream floods?

Answer 56

regional accumulations of water higher up in the drainage basin

Question 57

how does downstream flood differ from flashfloods?

Answer 57

1. lag time between the rain event and peak discharge (higher on downstream floods) 2. length of time the river remains above flood stage (higher on downstream floods)