Peak Discharge from Drainage Basin Runoff

Peak discharge from drainage basin runoff is the maximum flow rate of water passing through a specific point in a drainage system (like a river or stream) after a rainfall or snowmelt event.  It represents the highest volume of water per unit of time occurring at the outlet of a drainage basin or watershed during or after a storm.  Understanding peak discharge is used in hydrology for flood forecasting, designing stormwater management systems, and flood prevention strategies.

Key Points Influence Peak Discharge

Rainfall Intensity and Duration  -  More intense and prolonged rainfall will result in a higher peak discharge.
Basin Size and Shape  -  Larger and steeper basins tend to have a quicker and higher peak discharge due to the faster runoff.
Soil Type and Vegetation  -  Soils that absorb water slowly, along with minimal vegetation, lead to higher runoff and peak discharge.
Land Use and Urbanization  -  Urbanized areas with impervious surfaces (like concrete) prevent water infiltration, leading to quicker runoff and higher peak discharge.
Antecedent Moisture Conditions  -  Wet soils prior to rainfall will absorb less water, increasing the runoff and peak discharge.

 

Peak Discharge from Drainage Basin Runoff Formula
\( Q  \;=\;  c \; i \; A  \)
Symbol	English	Metric
\( Q \) = Vapor Mass Velocity of Tray Type Tower	\(cfm\)	-
\( c \) = Rational Method Runoff Coefficient	\(dimensionless\)	-
\( i \) = Rainfall Intensity	\(in\;/\;hr\)	-
\( A \) = Drainage Area	\(acre\)	-

 

Rational Method Runoff Coefficient
Ground Cover	Runoff Coefficient
Asphault Streets	0.7 - 0.95
Brick Streets	0.7 - 0.85
Buisness Areas	0.5 - 0.95
Concrete Streets	0.7 - 0.95
Cultivated Land	0.08 - 0.41
Forest	0.05 - 0.25
Industrial Area	0.5 - 0.9
Lawn	0.05 - 0.35
Meadow	0.1 - 0.5
Parks, Cemeteries	0.1 - 0.25
Pasture	0.12 - 0.62
Residential Area	0.3 - 0.75
Roofs	0.75 - 0.95
Unimproved Area	0.1 - 0.3