A* CIE Facts to Memorise

What is the main input in a drainage basin?

Precipitation.

What are the main outputs from a drainage basin?

Evaporation

What are the main stores in a drainage basin?

Interception storage

What are the main transfers in a drainage basin?

Infiltration

Which is the fastest transfer within a drainage basin?

Surface runoff or overland flow.

Which is the slowest transfer within a drainage basin?

Groundwater flow.

What is a flashy hydrograph?

A hydrograph with a short lag time

What is a subdued hydrograph?

A hydrograph with a long lag time and lower peak discharge.

What effect does urbanisation have on drainage basins?

It decreases infiltration and increases surface runoff.

What effect does afforestation have on drainage basins?

It increases interception and reduces surface runoff.

What effect do impermeable rocks have on drainage basins?

They reduce infiltration and increase runoff.

What effect do permeable rocks have on drainage basins?

They increase infiltration and groundwater storage.

What effect do steep slopes have on river discharge?

They encourage rapid runoff and a shorter lag time.

What effect does dense vegetation have on river discharge?

It increases interception and slows water transfer.

What causes a short lag time?

Urbanisation

What causes a long lag time?

Permeable rock

What happens when precipitation exceeds evapotranspiration?

A water surplus occurs.

What happens when evapotranspiration exceeds precipitation?

A water deficit occurs.

Which type of drainage basin is most likely to flood quickly?

A small urban basin with impermeable surfaces.

Which type of drainage basin is least likely to flood quickly?

A rural basin with permeable soils and dense vegetation.

What is the formula for discharge?

Discharge equals cross-sectional area multiplied by velocity.

What are the units used to measure discharge?

Cubic metres per second or cumecs.

Which factors increase flood risk in a drainage basin?

Urbanisation

Which factors reduce flood risk in a drainage basin?

Afforestation

What should you remember for a 10-mark drainage basin question?

Inputs

What should you remember for a hydrograph question?

Lag time

What should you remember for an evaluation question on flood risk?

Urbanisation increases runoff whereas vegetation and permeable geology reduce runoff.

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