Storm Hydrographs Flashcards
What is Stormflow?
The storms impact on river discharge
What is the rising limb of a storm hydrograph?
Increasing discharge mainly due to overland flow
What happens if peak discharge exceeds bankfull discharge?
The river bursts it banks leading to a fluvial flood (river flood)
What is the lag time?
Peak rainfall to peak discharge delay (the time it took the river to rise)
What is the falling limb of a storm hydrograph?
Decreasing discharge mainly due to reduced overland flow
What is baseflow?
“normal flow” due to groundwater input
What is a flashy hydrograph?
A hydrograph with a short lag time
What is a subdued hydrograph?
A hydrograph with a long lag time
What physical factors affect the shape of storm hydrographs?
- Steep relief
- Impermeable soil / rocks
- Saturated soil / rocks
- Hard dry soil
What does less infiltration and percolation lead to?
More overland flow and a flashy hydrograph
How can trees help lead to a subdued hydrograph?
The leaves act as an umbrella and slow/stop rain from reaching the ground, roots can also slow down the movement of water in the soil
What is drainage density?
The number of tributaries per km^2
What does a high drainage density result in?
Less chance of a flashy hydrograph as water drains more efficiently into the main river
What human factors can impact storm hydrographs?
Deforestation, urbanisation and other practices
What does contour ploughing do?
Decreases overland flow as the furrows obstruct water from flowing downhill
