3. Runoff and Hydrograph Flashcards
A graph showing the discharge versus yime past a specific point in river, channel or conduit carrying flow
Hydrograph
Plot of discharge over time
Hydrograph
Rainfall excess reaches the mainstream through ___ and ___
Overland and Channel flows
Normal discharge of the river, stream or channel also known as Groundwater runoff
Base flow
Volume of water reaching the river from surface runoff
Direct runoff
Also known as Surface runoff
Direct runoff
Called subsurface runoff
Interflow
Volume of water reaching the river through the soil or underlying rocks
Interflow
Difference between peak rainfall and peak discharge
Lag time
Height at which a flood could occur - variable from river to river
Bankfull discharge
How much water is in the river
Discharge line
Determined by topographic map
Drainage area
Length of perennial channels divided by drainage area
Drainage density
Also known as concentration curve
Rising limb
Represent the increase of discharge due to gradual build up of storage in channel over the catchment area
Rising limb
Inflection point on rising limb to falling limb
Crest segment
Indicates the peak flow or the maximum amount of flow at basin outlet
Crest Segment
From the point of inflect at the end of crest segment to base flow
Falling limb
Inflection point, represent the time at which the rain stopped
Falling limb
A simple method to estimate peak flow of runoff
Rational method
The time required by the water to flow from the most remote point to the mouth of the watershed once the soil has become saturated and minor depression filled
Time of concentration
It is influenced mainly by the length of flow and flow slope gradient
Time of Concentration
The ratio of the peak runoff to the rainfall intensity
Runoff coefficient
It is develops for uniform rainfall using triangular hydrographs
Soil conservation service method
In SCS Q means__
Runoff depth
In SCS D means___
Duration of excess rainfall
Lowest runoff potential
Soil A
Moderately low runoff potential
Soil B
Moderately high runoff potential
Soil C
Highest runoff potential
Soil D
Includes deep sands with very little silt and clay
Soil A
Mostly sandy soil less depth that A
Soil B
Comprising shallow soils and soil containing considerable clay and colloids
Soil C
Includes mostly clay of high swelling percent
Soil D
