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TitleInfluence of loss of gradient from postglacial uplift on Red River flood hazard, Manitoba, Canada
AuthorBrooks, G R; Thorleifson, L H; Lewis, C F M
SourceThe Holocene vol. 15, no. 3, 2005 p. 347-352,
Alt SeriesGeological Survey of Canada, Contribution Series 2003046
PublisherSAGE Publications
Mediapaper; on-line; digital
File formatpdf
NTS62H/03; 62H/04; 62H/05; 62H/06; 62H/11; 62H/12; 62H/13; 62H/14
AreaRed River; Lake Winnipeg; Red River Floodway; Assiniboine River; Winnipeg; Ste. Agathe; Morris; St. Jean Baptiste; Letellier; Emerson
Lat/Long WENS -97.7500 -97.0000 50.0000 49.0000
Subjectshydrogeology; isostatic rebound; flood potential; flood plains; paleohydrology; drainage systems; Quaternary
Illustrationslocation maps; graphs; sketch maps; time series
ProgramCanada-Manitoba Partnership Agreement on Red River Valley Flood Protection
Released2016 07 27
AbstractThe north-flowing, low-gradient section of the Red River in Manitoba has lost-60%/o of its valley gradient since 8 ka cal. BP. An existing hydraulic model of the modem Red River flood zone was used to examine the change in flood extent and depth of a discharge equivalent to the 1997 Red River flood (3970 m3/s) for scenarios of gradients at 8, 6, 4 and 2 ka cal. BP as well as 2 ka in the future. The modelling indicates a broad, shallow flood zone for all of the gradient scenarios, with extent and depth increasing over time. Between the 8 ka cal. BP and present-day scenarios, the flood zone increased from 1186 km2 to 1531 km2 (-29%/o) with depth increasing along four east-west cross-sections by 0.69 m (-61%), 0.91 m (-82%), 0.56 m (-64%) and 0.48 m (-86%). The flood extent and depths increased by a further 18 km2(--5%) and 0.04-0.06 m (2-5%), respectively, by 2 ka in the future. Most of these changes to the flood zone occurred between 8 and 2 ka cal. BP, reflecting an exponential loss of gradient. A rise in flood depth equivalent to that which occurred between 8 ka cal. BP and the present-day, is assessed as increasing the long-term flood hazard; in contrast, the slight rise in depth between the present-day and 2 ka in the future does not.