A - Hydrographs Flashcards
What is a storm or flood hydrograph?
A graph showing river changes over a short period.
What does a storm hydrograph measure?
The speed at which rainfall reaches the river channel.
How is discharge (Q) defined?
Volume of flow through a river cross-section per time.
What does the rising limb indicate in a hydrograph?
The amount of discharge and the speed of its increase.
When is the rising limb very steep?
In flash floods or small, rapid-response basins.
What is peak flow or discharge?
The highest discharge, often higher in larger basins.
How does basin shape affect infiltration rates?
Steep catchments have lower infiltration; flat catchments have higher infiltration.
What is lag time in a hydrograph?
The interval between peak rainfall and peak discharge.
What factors influence lag time?
Basin shape, steepness, and stream order.
What does the run-off curve reveal?
The relationship between overland flow and throughflow.
What conditions increase overland flow?
Low infiltration, high antecedent moisture, impermeable surfaces, and intense rainfall.
What is baseflow?
Seepage of groundwater into the channel, a slow, long-term discharge source.
What influences the recessional limb?
Basin size, geological composition, and local aquifers.
How do rainfall and basin size affect discharge?
Higher rainfall and larger basins increase discharge.
List one factor affecting flood hydrographs related to climate.
Rainfall total, intensity, and seasonality.
How do soils affect flooding?
Impermeable clay soils increase flooding.
What role does vegetation play in flooding?
Intercepts rainfall, reducing flood likelihood.
What does infiltration capacity affect?
Low infiltration capacity causes more overland flow.
How does rock type impact flood peaks?
Permeable rocks reduce flood peaks by allowing infiltration.
How does slope angle affect run-off?
Steeper slopes increase run-off.
What is drainage density?
Number of stream channels; higher density means more water enters rivers.
How do dams affect water flow?
Dams disrupt natural water flow.
How do urban hydrographs differ from rural ones?
Urban hydrographs have shorter lag times, steeper rising limbs, higher peaks, and steeper recessional limbs.
What causes the differences in urban hydrographs?
More impermeable surfaces and drainage channels in urban areas.
