1. Why do some rivers Flood?
Factors making a ‘flashy’ hydrograph

2. ‘Flashy’ and ‘Flat’ Hydrographs

3. Precipitation intensity
Torrential Rain
And so?
And so ?
Precipitation intensity

4. Precipitation intensity
Torrential Rain
Ground can’t absorb it fast enough – overland flow
Flash Flood
Precipitation intensity

5. Factor 1 – Precipitation intensity
Steady Rain
And so?
And so ?
Factor 1 – Precipitation intensity

6. Factor 1 – Precipitation type
snowfall
And so?
And so ?
snowfall
And so?
And so ?
Factor 1 – Precipitation type

7. Types of Underlying Rock
Granite is impermeable
And so
Types of Underlying Rock

8. Types of Underlying Rock
chalk and most limestones re permeable
And so
Types of Underlying Rock

9. Sand is permeable but clay is impermeable
And so
Soils

10. Soils – saturated / frozen
Sand and clay if saturated or frozen are impermeable
And so
Soils – saturated / frozen

11. Forest much interception
And so
Forested

12. Deforested no interception
And so
Deforested

13. Covers ground in impermeable materials
And so
Urbanisation

14. Installs storm drains
And so
Urbanisation