The recession limb of a flood hydrograph can be expressed with positive values of coefficients, as Q_{t}/Q_{0} =
Barnes showed that recession limp of a flood hydrograph can be expressed as,
where a = In k_{r}
k_{r} is recession constant of value less than unity. Q_{0} and Q_{t} are discharges at a time interval of t days with Q_{0} being the initial discharge.
For a given storm, other factors remaining same,
The drainage density is defined as the ratio of the total channel length to the total drainage area. A large drainage density creates situation conductive for quick disposal of runoff drawn the channels.
Baseflow separation is performed
A unit hydrograph has
The basic assumptions of the unithydrograph theory are
The Dhour unit hydrograph of a catchment may be obtained by dividing the ordinates of a single peak Direct Runoff Hydrograph (DRH) due to a storm of Dhour duration by the
A triangular DRH due to a storm has a time base of 80 hrs and a peak flow of 50 m^{3}/s occurring at 20 hours from the start, if the catchment area is 144 km^{2}, the rainfall excess in the storm was
A 12hr unit hydrograph of a catchment is triangular in shape with a base width of 144 hours and a peak discharge value of 23 m^{3}/s. This unit hydrograph refers to a catchment of area
Unit hydrograph refers to 1 cm of rainfall excess
∴ Let area of catchment = A(km^{2})
A 90 km^{2} catchment has a 4h unit hydrograph which can be approximated as a triangle. If the peak ordinate of this unit hydrograph is 10m^{3}/s the time base is
Let the time base = B(hours)
A triangular DRH due to a 6h storm in a catchment has a time base of 100 h and a peak flow of 40 m^{3}/s. The catchment area is 180 km^{2}. The 6h unit hydrograph of this catchment will have a peak flow in m^{3}/s of
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