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Coupled hydrogeomorphic and woody-seedling responses to controlled flood releases in a dryland river

Water Resources Research

By:
and
DOI: 10.1002/wrcr.20256

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Abstract

Interactions among flow, geomorphic processes, and riparian vegetation can strongly influence both channel form and vegetation communities. To investigate such interactions, we took advantage of a series of dam-managed flood releases that were designed in part to maintain a native riparian woodland system on a sand-bed, dryland river, the Bill Williams River, Arizona, USA. Our resulting multiyear flow experiment examined differential mortality among native and nonnative riparian seedlings, associated flood hydraulics and geomorphic changes, and the temporal evolution of feedbacks among vegetation, channel form, and hydraulics. We found that floods produced geomorphic and vegetation responses that varied with distance downstream of a dam, with scour and associated seedling mortality closer to the dam and aggradation and burial-induced mortality in a downstream reach. We also observed significantly greater mortality among nonnative tamarisk (Tamarix) seedlings than among native willow (Salix gooddingii) seedlings, reflecting the greater first-year growth of willow relative to tamarisk. When vegetation was small early in our study period, the effects of vegetation on flood hydraulics and on mediating flood-induced channel change were minimal. Vegetation growth in subsequent years resulted in stronger feedbacks, such that vegetation's stabilizing effect on bars and its drag effect on flow progressively increased, muting the geomorphic effects of a larger flood release. These observations suggest that the effectiveness of floods in producing geomorphic and ecological changes varies not only as a function of flood magnitude and duration, but also of antecedent vegetation density and size.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Coupled hydrogeomorphic and woody-seedling responses to controlled flood releases in a dryland river
Series title:
Water Resources Research
DOI:
10.1002/wrcr.20256
Volume
49
Issue:
5
Year Published:
2013
Language:
English
Publisher:
AGU
Contributing office(s):
Fort Collins Science Center
Description:
18 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Water Resources Research
First page:
2843
Last page:
2860
Country:
United States
State:
Arizona
Other Geospatial:
Bill Williams River