Lecture 20 Flashcards
Strath terraces
Eroded bedrock surface
Fill terraces
Surfaces of sediment
Elements of a river
Floodplain
River channel
Floodplain deposits
Bedrock
Floodplain
Where sediments are deposited when the stream rises above its channel banks
Nov 2010 flooding in NS
Hundred evacuated
Millions $ of damage
>250mm of rainfall in 4 days
Steam flooding
When a stream receives more water than it can usually transport
Either increases in cross sectional area or flows faster - both increases stream discharge
Two ways to predict flooding
1) Use complete record for all previous disasters
2) Use numerical model that is complex enough to consider all of the important controls on the hazard’s timing and magnitude
Return interval
Time between events of the same magnitude
Depends on the number of years over which you have observed the hazards, rank of the observed events
RI = (N+1)/M
N= number of years of flood records
M= numerical rank of event
Probability of flooding
Reciprocal of RI
Flood hydrograph
Shows stream surface elevation over time
Differences between rural and urban graphs
