1.8 River Flooding Flashcards
Why do river floods occur?
After a period of prolonged rainfall, causing river levels to rise. Or build up of melting snow.
What is river flooding?
When a river channel can no longer hold the amount of water flowing within it. Water overtops the banks and floods the adjacent land.
What are flash floods?
Floods after torrential storms and extreme rainfall.
What are some physical causes of river floods?
Rock type Steep slopes Long profile Drainage density Snowmelt Intense and prolonged rainfall Deforestation Agriculture Ineffective flood management and warning systems
Causes of river floods – rock type
Impermeable rocks incourage overland flow, which transfers water rapidly to river channels
Causes of river floods – steep slopes
Steep slopes such as mountain environments encourages a rapid transfer of water, by Overland flow and through flow
Causes of river floods – long profile
If a river has a steep upper course and a flat lower course, Water is transferred rapidly to the lowlands
Causes of river floods- drainage density
Water can reach channels quickly, speeding flooding
Causes of river floods- snowmelt
Form a store of water, when melted they increase flooding
Causes of river floods- intense and prolonged rainfall
Tropical storms, hurricanes, monsoons have potential to cause significant floods
Causes of river floods- deforestation
Less chance of interception, won’t be stored in trees
Causes of river floods- agriculture
Arable farming- period with no vegetation grown increasing runoff
Causes of river floods- ineffective flood management and warning systems
Lack of them, broken or not checked
What is a human cause of river flooding?
Building construction, such as building on floodplains which creates an impermeable surface (roads, concrete, Tarmac)
The severity or magnitude of a flood is generally related to its frequency
The higher the magnitude the the lower the frequency, rarer.