Stormwater quiz TR-55 CORRECT
100%
SCS - ANSWERSoil Conservation Service. Promoted control and prevention of soil erosion: issued TR-
55
Was TR-55 method designed to describe flows in drainage areas with a significant portion of flow
within stormwater sewers? - ANSWERNo, TR-55 is based on open and unconfined flow over land or
in channels
What is the key characteristic used to categorize soils into HSG - ANSWERminimum infiltration rate
What assumptions about the connectivity of imperviousness are used to develop CN values -
ANSWERAssume they are directly connected to the drainage system
Identify the variables in SCS runoff equation - ANSWERQ (runoff), P (rainfall), S(potential max
retention after runoff begins) and Ia (initial abstraction)
What are the units for Q in the SCS runoff equation - ANSWERin
What factors affect the curve number - ANSWERHydrologic soil group (HSG), Cover type, treatment,
hydrologic condition, antecedent runoff condition (ARC), connectivity of areas
What does 'treatment' mean with respect to the CN - ANSWERA cover type modifier to describe the
management of cultivated agricultural lands
Does runoff increase or decrease as CN increases - ANSWERincrease
What key factors affect the time of concentration (time for runoff to travel from the hydraulically
most distant point of the watershed to a point of interest)? - ANSWERSurface roughness, channel
shape and flow patterns, slope
100%
SCS - ANSWERSoil Conservation Service. Promoted control and prevention of soil erosion: issued TR-
55
Was TR-55 method designed to describe flows in drainage areas with a significant portion of flow
within stormwater sewers? - ANSWERNo, TR-55 is based on open and unconfined flow over land or
in channels
What is the key characteristic used to categorize soils into HSG - ANSWERminimum infiltration rate
What assumptions about the connectivity of imperviousness are used to develop CN values -
ANSWERAssume they are directly connected to the drainage system
Identify the variables in SCS runoff equation - ANSWERQ (runoff), P (rainfall), S(potential max
retention after runoff begins) and Ia (initial abstraction)
What are the units for Q in the SCS runoff equation - ANSWERin
What factors affect the curve number - ANSWERHydrologic soil group (HSG), Cover type, treatment,
hydrologic condition, antecedent runoff condition (ARC), connectivity of areas
What does 'treatment' mean with respect to the CN - ANSWERA cover type modifier to describe the
management of cultivated agricultural lands
Does runoff increase or decrease as CN increases - ANSWERincrease
What key factors affect the time of concentration (time for runoff to travel from the hydraulically
most distant point of the watershed to a point of interest)? - ANSWERSurface roughness, channel
shape and flow patterns, slope
