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Influence of loss of gradient from postglacial uplift on Red River flood hazard, Manitoba, Canada

Holocene

By:
, , and
DOI: 10.1191/0959683605hl804rp

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Abstract

The north-flowing, low-gradient section of the Red River in Manitoba has lost ???60% of its valley gradient since 8 ka cal. BP. An existing hydraulic model of the modern 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%) 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. ?? 2005 Edward Arnold (Publishers) Ltd.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Influence of loss of gradient from postglacial uplift on Red River flood hazard, Manitoba, Canada
Series title:
Holocene
DOI:
10.1191/0959683605hl804rp
Volume
15
Issue:
3
Year Published:
2005
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Holocene
First page:
347
Last page:
352