Deglacial Flood Origin of the Charleston Alluvial Fan, Lower Mississippi Alluvial Valley

Porter, Donna A.; Guccione, Margaret J.

doi:10.1006/qres.1994.1031

Cited by 27 publications

(9 citation statements)

References 3 publications

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“…Schumm et al (1994) attribute such variation to isolated geological controls in the channel bed and banks which constrain the planform development of some meander bends. more recently by Porter and Guccione (1994) interpret this feature as a coarse remnant large-magnitude flood deposit formed around 10·9 ka BP when proglacial lakes Agassiz and Superior discharged their meltwater into the Mississippi River. Throughout the Holocene, the Lower Mississippi River has flowed in a single meander belt throughout this reach between the Charleston alluvial fan to the west and the loess bluff line to the east.…”

Section: Objective/statistical Reach Dynamics -Meander Trainsmentioning

confidence: 96%

Planform dynamics of the Lower Mississippi River

Harmar

Clifford

2006

Earth Surf Processes Landf

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This paper presents an analysis of the planform behaviour of the Lower Mississippi River (LMR) using a series of maps and hydrographic surveys covering the period 1765-1975. Data allow analysis at various time and space scales, using fixed and statistically defined reaches, both before and after extensive channel modification. Previous research has interpreted planform change in relation to geomorphological or engineering regime-type analyses of channel length and width for the LMR as a 'single system'. The analysis here is broadly consistent with these approaches, but highlights the importance of meander geometry, in the form of the radius of curvature:width ratio. This neglected factor helps resolve paradoxes relating to observed changes in sediment transport and channel stability. When viewed over smaller time and space scales, analysis of dynamics using fixed reach boundaries reveals a downstream trend in the pattern of planform behaviour, which is closely related to the distribution of valley floor deposits, and which also reflects neotectonic influences. Analysis of changes using statistically determined reach boundaries shows that, over shorter time scales, meander trains are continually formed and modified over a period of approximately 120 years. Zones of more-or-less dynamic behaviour thus move through the LMR. The research also provides a context for 20th century engineering interventions to the river. These have constrained the magnitude of planform adjustment, but also altered the kind of response that is now possible in relation to changes in discharge and sediment load, and as a consequence of internal feedbacks within the LMR system. A long-term planform record does exist, however, for the Lower Mississippi River. This provides a rare opportunity to analyse planform dynamics within their spatial and temporal context, and to offer explanations based upon the distribution of geological and neotectonic controls, changing discharge and sediment load regimes, and contrasting channel management strategies. In this paper, planform changes are studied between 1765 and 1975 using a sequence of planform maps, historic hydrographic surveys, long-term hydrological records and maps of abandoned channels in the Lower Mississippi alluvial valley. The period 1765-1975 is of particular interest because it combines both a phase of accelerated dynamics (in relation to average rates over the preceding several thousand years; Saucier, 1994), with a phase of constrained dynamics following channel shortening and bank stabilization in the 20th century.The purpose of this paper is twofold: to evaluate the complexity of planform dynamics by undertaking a multiscaled investigation using a unique large-scale and long-term planform record; and to improve understanding of the pre-modification planform dynamics of the Lower Mississippi River to inform shorter-term studies of geomorphological response to channel intervention. Analysis and discussion address the following research questions: (i) the extent to which planfo...

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Section: Objective/statistical Reach Dynamics -Meander Trainsmentioning

confidence: 96%

Planform dynamics of the Lower Mississippi River

Harmar

Clifford

2006

Earth Surf Processes Landf

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“…1). Second, more localised evidence of aggradation in this zone is provided by the Charleston alluvial fan deposit, formed around 10.9 kA BP (Porter and Guccione, 1994). Third, evidence of coarser bed material in the zone immediately downstream from Cairo is provided by the 1932 median grain size (Fig.…”

Section: Variation In Profile Slope At the Reach-scalementioning

confidence: 97%

Geomorphological explanation of the long profile of the Lower Mississippi River

Harmar

Clifford

2007

Geomorphology

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“…However, alluvial channels may also adjust their morphologies in response to wider climatic, land use and other anthropogenic changes in the drainage basin as well as to regional and local geological controls (Werritty, 1997). In terms of hydrological changes, considerable changes in the magnitude and frequency of major flood events on the Lower Mississippi River have been well documented at times of climatic amelioration such as the end of the Wisconsin glacial period (Teller, 1990;Porter and Guccione, 1994). However, during the post-European settlement period, anthropogenic influences throughout the drainage basin may be associated with more subtle variations in the flow regime.…”

Section: Discharge Sediment Supply and Tectonic Influencesmentioning

confidence: 97%

Morphological changes of the Lower Mississippi River: geomorphological response to engineering intervention

et al. 2005

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During the twentieth century, the planform and profile of the Lower Mississippi River from Cairo, Illinois, to New Orleans, Louisiana, have been transformed by a series of engineering modifications. These include steepening of the long profile by removal of the most sinuous bends, extensive bank stabilization, and regulating sediment movement by dyke field construction. Prior to these modifications, the Lower Mississippi River adjusted its morphology in the planform, long profile and crosssection. Planform adjustment has, however, effectively been negated and other adjustments are now constrained. Nevertheless, analysis of hydrographic surveys between 1949 and 1989 demonstrates that geomorphological response during the post-cutoff period remained complex. Morphological adjustments involved phased patterns of aggradation and degradation, together with changes in cross-sectional form, and in the number, size, location and shape of pools and crossings. Greatest changes occurred in the early post-cutoff period (1949-64) upstream from Vicksburg, Mississippi, but were accompanied by complementary changes elsewhere which propagated downstream. The combined set of responses may be interpreted with respect to a dynamic equilibrium in which the river responded to additional energy created by the cutoffs by increasing and adapting flow resistance over various scales and time periods. This study helps resolve paradoxes from previous analyses, and has significance for interpreting past engineering impacts and for suggesting future management strategies for the Lower Mississippi River.

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Deglacial Flood Origin of the Charleston Alluvial Fan, Lower Mississippi Alluvial Valley

Cited by 27 publications

References 3 publications

Planform dynamics of the Lower Mississippi River

Planform dynamics of the Lower Mississippi River

Geomorphological explanation of the long profile of the Lower Mississippi River

Morphological changes of the Lower Mississippi River: geomorphological response to engineering intervention

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