Influence of loss of gradient from postglacial uplift on Red River flood hazard, Manitoba, Canada
Holocene
By: G. R. Brooks, L. Harvey Thorleifson, and C.F.M. Lewis
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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.
Suggested Citation
Brooks, G.R., Thorleifson, L.H., Lewis, C., 2005, Influence of loss of gradient from postglacial uplift on Red River flood hazard, Manitoba, Canada: Holocene, v. 15, no. 3, p. 347-352, https://doi.org/10.1191/0959683605hl804rp.
| 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 |
| Publication Date | April 01, 2005 |
| Year Published | 2005 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Holocene |
| First page | 347 |
| Last page | 352 |