Stormwater Exam 1 UPDATED ACTUAL
Questions and CORRECT Answers
List the elements of the hydrologic cycle - CORRECT ANSWER - Precipitation,
evaporation, condensation, infiltration, runoff, transpiration, sublimation, groundwater flow
About how much does air temperature change with every 1000ft increase in elevation under
sunny conditions - CORRECT ANSWER - 5.4 F decrease
We mentioned ways in which air lifting occurs. Know/describe these. - CORRECT
ANSWER - Cyclonic lifting - warm front moving in causing warm air to rise gradually or
cold front moving in causing warm air to rise quickly
Frontal activity - occurs when warm and cold air masses meet causing the warm air to rise over
the cooler air
Convection - Instabilities in atmosphere by uneven heating
Orographic - Mechanical lifting by mountains
Why do raindrops rarely exceed 5mm diameter - CORRECT ANSWER - They get too
heavy and start breaking apart
How many hours without rainfall are commonly used to differentiate between storm events -
CORRECT ANSWER -6
What happens (type of storm event) when a cold air mass encounters a warm air mass? How
about vice versa? - CORRECT ANSWER - Cold meets warm - Cold front (thunderstorms)
Warm meets cold - Warm front (continuous rain)
From a stormwater management standpoint when will I be most interested in each of the
following? a) rainfall intensity b) rainfall depth - CORRECT ANSWER - a) duration
controls intensity need for infiltration b) return period controls depth need for long term
management
,What is a hyetograph - CORRECT ANSWER - A graph that displays rainfall intensity and
how it varies with time
What is a rainfall intensity curve - CORRECT ANSWER - a graphical representation that
shows the relationship between rainfall intensity and the duration of the rainfall event
What types of storm shapes are common in Knoxville and what does it mean in terms of storm
rainfall distribution - CORRECT ANSWER - Type 2 storms are most common in which
high intensity rainfall is experienced in short duration
Describe the "Type 2" storm shape - CORRECT ANSWER - Rainfall has a rapid rise to
maximum intensity followed by a gradual decline, most of the rainfall is in the middle of the
storm
How does expected rainfall intensity change with an increase in the area of interest? -
CORRECT ANSWER - As AOI increases, rainfall intensity decreases
How does expected rainfall intensity change with an increase in the time period of interest -
CORRECT ANSWER - It decreases
What would it mean to say that a storm depth is the 95th percentile depth - CORRECT
ANSWER - 95% of storms have a depth that is less than or equal to this value
Define what is meant by a 2-yr 10-hr storm - CORRECT ANSWER - A 2-yr 10-hr storm is
a rainfall event that is expected to occur once every two years and lasts for 10 hours.
How dies an increase in duration effect a storm probabilistically - CORRECT ANSWER -
Higher chances of extreme rainfall and significant runoff
, How dies an increase in return period effect a storm probabilistically - CORRECT
ANSWER - As the return period increases the intensity decreases
Which of the following will occur more often?
___ 2-yr 30-minute storm
___ 100-yr 2-hr storm
___ 1-yr 1-minute storm
___ can't tell, given the information provided - CORRECT ANSWER - 1-yr 1-minute
storm
Do we generally want rain gages placed on a pattern or more evenly distributed? Why? -
CORRECT ANSWER - More evenly distributed rain gauges provide more accuracy
because it helps capture localized differences in precipitation which occurs due to topography,
land use, and weather patterns
If rain gages were placed at the density suggested by the Weather Bureau for "general
meteorology", how far apart would the gages be? - CORRECT ANSWER - 600km^2
What kinds of environmental conditions would I likely need to have more rain gauges -
CORRECT ANSWER - Mountainous regions and areas with drastic climatic changes
relative to the observed area
If I have storm rainfall values at several locations nearby, what is a procedure that I can use to
estimate what the rainfall was here? - CORRECT ANSWER - Spatial statistics
If I have storm rainfall values at several locations nearby, what is a procedure that I can use to
get an average rainfall depth over the entire area - CORRECT ANSWER - add pic
What is the primary reason to estimate infiltration - CORRECT ANSWER - Because high
infiltration rate at the beginning of smaller storms is important
Questions and CORRECT Answers
List the elements of the hydrologic cycle - CORRECT ANSWER - Precipitation,
evaporation, condensation, infiltration, runoff, transpiration, sublimation, groundwater flow
About how much does air temperature change with every 1000ft increase in elevation under
sunny conditions - CORRECT ANSWER - 5.4 F decrease
We mentioned ways in which air lifting occurs. Know/describe these. - CORRECT
ANSWER - Cyclonic lifting - warm front moving in causing warm air to rise gradually or
cold front moving in causing warm air to rise quickly
Frontal activity - occurs when warm and cold air masses meet causing the warm air to rise over
the cooler air
Convection - Instabilities in atmosphere by uneven heating
Orographic - Mechanical lifting by mountains
Why do raindrops rarely exceed 5mm diameter - CORRECT ANSWER - They get too
heavy and start breaking apart
How many hours without rainfall are commonly used to differentiate between storm events -
CORRECT ANSWER -6
What happens (type of storm event) when a cold air mass encounters a warm air mass? How
about vice versa? - CORRECT ANSWER - Cold meets warm - Cold front (thunderstorms)
Warm meets cold - Warm front (continuous rain)
From a stormwater management standpoint when will I be most interested in each of the
following? a) rainfall intensity b) rainfall depth - CORRECT ANSWER - a) duration
controls intensity need for infiltration b) return period controls depth need for long term
management
,What is a hyetograph - CORRECT ANSWER - A graph that displays rainfall intensity and
how it varies with time
What is a rainfall intensity curve - CORRECT ANSWER - a graphical representation that
shows the relationship between rainfall intensity and the duration of the rainfall event
What types of storm shapes are common in Knoxville and what does it mean in terms of storm
rainfall distribution - CORRECT ANSWER - Type 2 storms are most common in which
high intensity rainfall is experienced in short duration
Describe the "Type 2" storm shape - CORRECT ANSWER - Rainfall has a rapid rise to
maximum intensity followed by a gradual decline, most of the rainfall is in the middle of the
storm
How does expected rainfall intensity change with an increase in the area of interest? -
CORRECT ANSWER - As AOI increases, rainfall intensity decreases
How does expected rainfall intensity change with an increase in the time period of interest -
CORRECT ANSWER - It decreases
What would it mean to say that a storm depth is the 95th percentile depth - CORRECT
ANSWER - 95% of storms have a depth that is less than or equal to this value
Define what is meant by a 2-yr 10-hr storm - CORRECT ANSWER - A 2-yr 10-hr storm is
a rainfall event that is expected to occur once every two years and lasts for 10 hours.
How dies an increase in duration effect a storm probabilistically - CORRECT ANSWER -
Higher chances of extreme rainfall and significant runoff
, How dies an increase in return period effect a storm probabilistically - CORRECT
ANSWER - As the return period increases the intensity decreases
Which of the following will occur more often?
___ 2-yr 30-minute storm
___ 100-yr 2-hr storm
___ 1-yr 1-minute storm
___ can't tell, given the information provided - CORRECT ANSWER - 1-yr 1-minute
storm
Do we generally want rain gages placed on a pattern or more evenly distributed? Why? -
CORRECT ANSWER - More evenly distributed rain gauges provide more accuracy
because it helps capture localized differences in precipitation which occurs due to topography,
land use, and weather patterns
If rain gages were placed at the density suggested by the Weather Bureau for "general
meteorology", how far apart would the gages be? - CORRECT ANSWER - 600km^2
What kinds of environmental conditions would I likely need to have more rain gauges -
CORRECT ANSWER - Mountainous regions and areas with drastic climatic changes
relative to the observed area
If I have storm rainfall values at several locations nearby, what is a procedure that I can use to
estimate what the rainfall was here? - CORRECT ANSWER - Spatial statistics
If I have storm rainfall values at several locations nearby, what is a procedure that I can use to
get an average rainfall depth over the entire area - CORRECT ANSWER - add pic
What is the primary reason to estimate infiltration - CORRECT ANSWER - Because high
infiltration rate at the beginning of smaller storms is important
