Assessing the effects of alternative setback channel constraint scenarios employing a river meander migration model

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TitleAssessing the effects of alternative setback channel constraint scenarios employing a river meander migration model
Publication TypeJournal Article
Year of Publication2006
AuthorsLarsen EW, Girvetz EH, Fremier AK
JournalEnvironmental Management
Volume37
Pagination880-897
Date PublishedJun
Type of ArticleArticle
ISBN Number0364-152X
Accession NumberISI:000236972900011
KeywordsBED-LOAD SEDIMENT, constraint setback, dynamics, ECOSYSTEMS, FLOODPLAIN, FLOW, GEOMORPHIC PROCESSES, hydraulic simulation model, MISSOURI RIVER, oxbow lake, RESTORATION, RIPARIAN VEGETATION, river, river meander migration, Sacramento River, setback levee, USA
Abstract

River channel migration and cutoff events within large river riparian corridors create heterogeneous and biologically diverse landscapes. However, channel stabilization (riprap and levees) impede the formation and maintenance of riparian areas. These impacts can be mitigated by setting channel constraints away from the channel. Using a meander migration model to measure land affected, we examined the relationship between setback distance and riparian and off-channel aquatic habitat formation on a 28-km reach of the Sacramento River, California, USA. We simulated 100 years of channel migration and cutoff events using 11 setback scenarios: 1 with existing riprap and 10 assuming setback constraints from about 0.5 to 4 bankfull channel widths (bankfull width: 235 m) from the channel. The percentage of land reworked by the river in 100 years relative to current (riprap) conditions ranged from 172% for the 100-m constraint setback scenario to 790% for the 800-m scenario. Three basic patterns occur as the setback distance increases due to different migration and cutoff dynamics: complete restriction of cutoffs, partial restriction of cutoffs, and no restriction of cutoffs. Complete cutoff restriction occurred at distances less than about one bankfull channel width (235 m), and no cutoff restriction occurred at distances greater than about three bankfull widths (similar to 700 m). Managing for point bars alone allows the setbacks to be narrower than managing for cutoffs and aquatic habitat. Results suggest that site-specific "restriction of cutoff" thresholds can be identified to optimize habitat benefits versus cost of acquired land along rivers affected by migration processes.

Short TitleEnviron. Manage.
Alternate JournalEnviron. Manage.

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Original

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