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Unformatted text preview: y in London
April 26, 1937. The disaster that defined an era.
Rain pushed the Thames 7 m above normal, spilling surging water
over hundreds of hectares in west London (along Wharncliffe Road).
It left one person dead and almost $1 million in damage
19 What caused it? precipitation: not all water can be
accommodated; so much, can't be soaked in, rest as runoff
Flooding: - inﬁltration: cement from buildings prevent water from Factors governing flooding:
• Land use being soaked into grown, no where to go
topography: ﬂat land, no where for water to go
vegetation: less erosion, absorbes water in roots, holes in
20 soil - small floods, more frequents, rare floods (10 year, hund.)
less frequent Magnitude and frequency
Hydrograph Flood frequency curve
>100 cm3 sec-1
21 7 - due to level of terraces - ceceptible risk: willing to live in areas where will not
100 years Terrace 2 1–2 years Terrace 1 Old channel
alluvium 1 in 100
“100 year flood” is actually the “__-__-____chance flood”
Buildings and infrastructure should be built above this level.
22 Gathering evidence of ancient floods:
Paleolimnology - didn't hear as much about ﬂood in Edmonton
because of ﬂood plan, city planning A longer
record of river
predictions - geological record - evidence of ﬂooding in past
Vermont flooding 1927 - take bits of wood, radio carbon testing 23 - more urbanized, shorter leg time, precip and runoff - time between rain fall and ﬂooding, less warning Urbanization and Flooding
• changes rainfall-runoff
• reduces lag time
• increasesdischarge (and
_________ peak runoff) Increased flooding:
• frequency 24 8 - restore soil to natural state (to inﬁltrate water) Adjustments to Flood Hazards - regulate ﬂooding areas (ex close to river=recreation) Physical Barriers & Channel restoration
Changing __________ - ppl more aware of areas more pron to ﬂood, wont live there
- prevent damage from happening from floods: flooding is
25 - modify human behaviour: not give insurance when you're in area that could be in danger of flooring (flood plain)
- make regulations in cities (Edmonton vs Calgary: green space, not huge inconv
- change in perceptions - # of approaches to protect against ﬂood...
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- Fall '14