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Flashcards in Floods Deck (11):
1

Threshold Exceedence

a peak discharge that exceeds a given threshold

2

Annual maximum flood

the highest discharge in any one year

3

Mean annual flood

an index of cental tendency of the distribution of flood magnitudes. often estimated by averaging the series of annual maximum floods

4

T-year return period flood

an index based on the upper tail of the distribution of flood magnitudes

5

Data problems

floods are hard to measure in the field, rarity mean few opportunities to calibrate

6

average frequencies

need long records to define even moderate return periods

7

interpretation problems

tendency to equate return period with a forecast by an event mat occur in less time or may not even occur

8

Multi0decadal variability

clustering of relatively flood-rich and flood poor epochs

9

Non-stationarity

- catchment changed imply differing consequences through time
- past may not be representative of the future

10

Impact of urbanisation on floods

- increases flood frequency, more floods
- accelerates due to improved drainage, earlier peak flow
- magnifies due to more impermeable surfaces, higher peak flow
- reduces sensitivity to antecedent conditions

11

approaches to mitigate floods

- permeable pavement
- water filled tube
- restoration of original meanders and floodplain from straightened rivers
- demountable wall