12 37 p 353 100 yr floodplain floodway fringe

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Unformatted text preview: Ice Dam Floods Red River, ND 1997 March 26 - May 20 >$1 billion clean-up costs 60,000 people evacuated in Grand Forks area 11 deaths Location of glacial Lake Agassiz (9,800 yrs ago) controlled flooded area Ice Jam Threatens Bridge Gorham, NH Fig. 12- 37, p. 353 100- yr Floodplain: Floodway & Fringe Recurrence Interval & Chance of Recurrence in any given year Recurrence Interval Problems with Recurrence Intervals §༊  §༊  Must be long enough to be representaLve Assumes that upstream condi1ons were similar through Lme §༊  §༊  §༊  Climate changes Human impacts All floods ploOed should originate from similar causes for random distribuLon of flood sizes Paleoflood Analysis Urbaniza1on LA ‘River’ Fig. 13- 2, p. 365 Impervious Surfaces Bridges §༊  §༊  §༊  Raise roadway...
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