Hydrographs Flashcards
What does base flow represent?
The normal day to day discharge of the river and is the consequence of groundwater seeping into the river channel.
What does the rising limb represent?
The increase in river discharge caused from surface runoff and through flow.
What does the peak discharge represent?
When the river is at its highest point.
What does lag time represent?
The time between the peak rainfall and the peak discharge.
What does the falling limb represent?
When the discharge decreases and the river level falls.
How does geology affect the response of a river to a storm event?
Impermeable rock = more overland flow, less through flow and infiltration
How does permeable affect the response of a river to a storm event?
High infiltration capacity - water will be absorbed quicker, reducing overland flow - results in longer lag time
How does heavy rain affect lag time?
Rapid saturation of the upper soil layers
excess water, surface runoff - short lag time
How does vegetated areas affect the response of a river?
Intercept rainfall - hold water on its leaves - slowing movement of water to river
Evapotranspiration
What is a river regime?
Where flood hydrographs are used to show the annual discharge for a given river - the annual patterns of river discharge
How does urban growth affect the response of a river?
Concrete surfaces increase overland flow and reduce infiltration
How does water abstraction affect the response of a river?
Reduces the base flow do moor water must reach the channel before it reaches full baneful capacity
How does afforestation affect the response of a river?
Interception is increased, while evapotranspiration reduces how much water reaches the river
What influences the flood hydrograph?
Both human and physical factors
What are the physical influences of a flood hydrographc?
Size and shape of drainage basin
Steeper hills - water will run faster (flashy graph)
Rate of precipitation
Drainage density (number of rivers within an area)
Saturation
Rock type - impermeability of rock
Vegetation cover - intercept rainfall
