Lesson 8 - Physical Causes of Flooding Flashcards
What are the 5 main physical causes of flooding?
Prolonged heavy rainfall
Seasonal monsoon rainfall
Intense storms
Snow + Ice
Local/Secondary causes
How does prolonged heavy rainfall result in flooding?
Passage of low pressure systems or depressions causes high rainfall
Can have cumulative effect on drainage basin
What is this sequence of depressions known as?
The Progressive Cycle
How does the Jet Stream influence the Progressive Cycle?
Position of the Jet Stream may change the time at which PC occurs
Usually occurs in Autumn
How does seasonal monsoon rainfall result in flooding?
Intense seasonal rainfall
Large stress on low lying areas
Little time to adapt
How do intense storms result in flooding?
Risk of flash flooding
Rapid change in river discharge
How do snow + ice result in flooding?
Seasonal snow melt
Downstream regions remain frozen - infiltration is minimal
Floodwater sometimes released by melting ice dams
Which type of flooding are snow and ice most liable for?
Glacial Outburst Floods
Ice dams melt/overwhelmed
Which local condition tend to increase flood risk?
Soil type
Geology
Vegetation
Topography
Speed of onset
Peak flow
What are the 4 main types of flood?
Surface Water Flooding
Groundwater Flooding
Flash Flooding
Jokulhalup
What is Surface Water flooding?
Intense rainfall, not enough time for infiltration
What is Groundwater flooding?
Occurs due to saturated ground
What is Flash flooding?
Flood with exceptionally short lag time
What is a Jokulhalup?
Glacial outburst flood
Occurs when glacial dam fails
