Synthetic Unit Hydrographs Flashcards
What are some of the major βeventsβ that
can occur in a hydrological system? How
long do they typically last?
- Flood Events
- Runoff Events
- Rainfall Events
What axis is a hydrograph graphed on
X- axis = Time
Y-axis = Flow Rate
What variables is used to define the peak flow on the hydrograph
tp
Qp
What is the area under the hydrograph
Flow Volume
To understand runoff properties:
- observe a storm (precipitation + runoff).
- construct unit hydrograph (deconvolution).
- predict runoff from future storms (convolution with UH).
What is the main motivation for the
construction of a synthetic hydrograph?
Allows a comparison between a gauged catchment and
an un-gauged catchment
What are some limitations of Synthetic UH
- Empirical method. It is not a description of the underlying physics of flowing water.
- Event-centric method. Rainfall and runoff are considered in isolation from other
catchment conditions. How long since the last rain? What are the soil conditions? Is
baseflow high or low?
To go beyond these limits, we need to reimagine catchment models from physical
principles.
What is Ct
is a measure of the variation in topography
What is tr
π‘π = rainfall duration [h
What is tp
π‘π = time to peak runoff [h]
What is qp
ππ = peak runoff per unit basin area per
unit rainfall [m3
/s/km2
/cm]
What is Cp
- Cp measure of flood wave and storage conditions
- lower Cp often means higher Ct
- values range from < 0.1 to > 1.2 (usually 0.4-0.8)
What is W50,75
W50,75 = widths, 50 & 75% of peak runoff [h]
What is tR
π‘π = Required rainfall duration [h]
What is tpR
π‘ππ = Required time to peak runoff [h]
