The disaster that defined an era rain pushed the

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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: • Precipitation • Infiltration • Topography • Snowmelt • Vegetation • 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 Discharge: >100 cm3 sec-1 4-6 years 21 7 - due to level of terraces - ceceptible risk: willing to live in areas where will not 500 years 100 years Terrace 2 1–2 years Terrace 1 Old channel Channel Floodplain 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 discharge increases the accuracy of ________ flood 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 patterns • reduces lag time • increasesdischarge (and _________ peak runoff) Increased flooding: • magnitude • 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 Insurance Regulations perceptions Changing __________ - ppl more aware of areas more pron to flood, wont live there *flood plain - prevent damage from happening from floods: flooding is natural process 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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