Lecture 6b

Question 1

why use unit hydrographs

Answer 1

to translate rainfall excess into catchment outlet flow rates

Question 2

what is a unit hydrograph

Answer 2

a unit hydrograph represents the characteristic flow rate response of a watershed to 1cm (or 1in) of rainfall excess occurring over a defined time step

Question 3

steps of hydrograph synthesis

Answer 3

input rainfall.
account for abstractions.
rainfall excess hyetograph.
convert to runoff.
direct runoff hydrograph.
add baseflow.
total runoff hydrograph.

Question 4

how can unit hydrographs be generated

Answer 4

either by using measured flow and rainfall data or empirical equations relating runoff response to physical catchment attributes.

Question 5

Unit Hydrograph Examples Include

Answer 5

SCS Unit Hydrograph
Snyder Unit Hydrograph
Clark Unit Hydrograph

Question 6

the scs unit hydrograph can be formulated as either…

Answer 6

triangular or curvilinear

Question 7

in convolution the UH is treated as a

Answer 7

linear scalar

Question 8

how do you generate a storm hydrograph with a unit hydrograph

Answer 8

convolution

Question 9

what condition is required for convolution

Answer 9

equal time steps

Question 10

what assumption is made when treating UH as a linear scalar

Answer 10

the time base remains the same (this is a major assumption)

Question 11

What are two methods to generate a unit hydrograph

Answer 11

deconvolution of a measured runoff hydrograph and empirical equations using catchment parameters