气候变化领域集成服务门户(CCPortal): Flood Variability Determines the Location of Lobe-Scale Avulsions on Deltas: Madagascar

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DOI	10.1029/2020GL088797
	Flood Variability Determines the Location of Lobe-Scale Avulsions on Deltas: Madagascar
	Brooke S.A.S.; Ganti V.; Chadwick A.J.; Lamb M.P.
发表日期	2020
ISSN	0094-8276
卷号	47 期号:20
英文摘要	River deltas grow through repeated lobe-scale avulsions, which often occur at a location that correlates with the backwater lengthscale. Competing hypotheses attribute the avulsion node origin to either the morphodynamic feedbacks caused by natural flood discharge variability (backwater hypothesis) or to the prograding delta lobe geometry (geometric hypothesis). Here, using theory, historical flood records, and remotely sensed elevation data, we analyzed five lobe-scale delta avulsions in Madagascar, captured by Landsat imagery. Avulsion lengths were 5–55 km, distances significantly longer than the backwater lengthscale and inconsistent with the geometric hypothesis. We show that the steep, silt-bedded rivers of Madagascar have flood-induced bed scour, driven by backwater hydrodynamics, that propagates farther upstream than the backwater lengthscale. The avulsion lengths are 3.1 ± 1.5 times the predicted flood scour lengths, similar to low-gradient deltas, and consistent with backwater hypothesis. Results demonstrate that erosion initiated by nonuniform flows in the backwater zone is a primary control on delta avulsion locations. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	Floods; Geometry; Location; Scour; Elevation data; Historical flood records; Landsat imagery; Length scale; Natural flood; Non-uniform flows; Primary control; River deltas; Water; avulsion; backwater; discharge; elevation; flood; hypothesis testing; Landsat; morphodynamics; remote sensing; satellite imagery; Madagascar
语种	英语
来源期刊	Geophysical Research Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/169604
作者单位	Department of Geography, University of California Santa Barbara, Santa Barbara, CA, United States; Department of Earth Science, University of California Santa Barbara, Santa Barbara, CA, United States; Department of Earth Sciences and St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN, United States; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, United States
推荐引用方式 GB/T 7714	Brooke S.A.S.,Ganti V.,Chadwick A.J.,et al. Flood Variability Determines the Location of Lobe-Scale Avulsions on Deltas: Madagascar[J],2020,47(20).
APA	Brooke S.A.S.,Ganti V.,Chadwick A.J.,&Lamb M.P..(2020).Flood Variability Determines the Location of Lobe-Scale Avulsions on Deltas: Madagascar.Geophysical Research Letters,47(20).
MLA	Brooke S.A.S.,et al."Flood Variability Determines the Location of Lobe-Scale Avulsions on Deltas: Madagascar".Geophysical Research Letters 47.20(2020).