Meander Scars as Evidence of Major Climate Change in Southwest Louisiana

Alford, John J.; Holmes, Joseph C.

doi:10.1111/j.1467-8306.1985.tb00074.x

Cited by 65 publications

(35 citation statements)

References 15 publications

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“…Theoretical, experimental and field studies suggest that changes in meandering or channel planform are the primary mode of response in many rivers (Alford and Holmes, 1985;Autin, 1992;Koss et al, 1994;Leigh and Feeney, 1995;Schumm, 1992). An increase in sinuousity upstream of a new baselevel would have the effect of reducing slope without any necessary change in bed elevation in the lower river.…”

Section: Spatial and Temporal Propagationmentioning

confidence: 95%

Channel adjustments of the lower Trinity River, Texas, downstream of Livingston Dam

Phillips

Slattery

Musselman

2005

Earth Surf Processes Landf

135

106

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Channel cross-sectional changes since construction of Livingston Dam and Lake Livingston in 1968 were studied in the lower Trinity River, Texas, to test theoretical models of channel adjustment, and to determine controls on the spatial extent of channel response. High and average flows were not significantly modified by the dam, but sediment transport is greatly reduced. The study is treated as an opportunistic experiment to examine the effects of a reduction in sediment supply when discharge regime is unchanged. Channel scour is evident for about 60 km downstream, and the general phenomena of incision, widening, coarsening of channel sediment and a decrease in channel slope are successfully predicted, in a qualitative sense, by standard models of channel response. However, there is no consistent channel response within this reach, as various qualitatively different combinations of increases, decreases or no change in width, depth, slope and roughness occur. These multiple modes of adjustment are predicted by the unstable hydraulic geometry model. Between about 60 km and the Trinity delta 175 km downstream of the dam, no morphological response to the dam is observed. Rather than a diminution of the dam's effects on fluvial processes, this is due to a fundamental change in controls of the fluvial system. The downstream end of the scour zone corresponds to the upstream extent of channel response to Holocene sea level rise. Beyond 60 km downstream, the Trinity River is characterized by extensive sediment storage and reduced conveyance capacity, so that even after dam construction sediment supply still exceeds transport capacity. The channel bed of much of this reach is near or below sea level, so that sea level rise and backwater effects from the estuary are more important controls on the fluvial system than upstream inputs.

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Section: Spatial and Temporal Propagationmentioning

confidence: 95%

Channel adjustments of the lower Trinity River, Texas, downstream of Livingston Dam

Phillips

Slattery

Musselman

2005

Earth Surf Processes Landf

135

106

View full text Add to dashboard Cite

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“…Aerial photographs show obvious palaeomeanders in the Trinity Valley, expressed as swampy depressions or meander scrolls. These occur on the Deweyville surfaces, with radii of curvature and amplitudes suggesting significantly larger palaeodischarges than at present (Alford and Holmes, 1985;Blum et al, 1995). In the lowermost Trinity, Shafer (1966) dates the Deweyville terraces at 5-7 Ka; and Alford and Holmes (1985), in the nearby Sabine River, at 4-9 Ka.…”

Section: Alluvial Terracesmentioning

confidence: 93%

“…In most locations two (Shafer, 1966), 'at least two' (Blum and Price, 1998) or three (Blum et al, 1995;Morton et al, 1996;Rodriguez et al, 2005) separate 'Deweyville' surfaces are recognized. The lowermost Deweyville surfaces are only slightly higher than the modern floodplain, and in some cases are buried by the latter, with natural levees of the modern floodplain higher than backswamps of the lower Deweyville (Alford and Holmes, 1985;Blum et al, 1995;Rodriguez et al, 2005). Aerial photographs show obvious palaeomeanders in the Trinity Valley, expressed as swampy depressions or meander scrolls.…”

Section: Alluvial Terracesmentioning

confidence: 95%

Antecedent alluvial morphology and sea‐level controls on form‐process transition zones in the lower Trinity river, Texas

Phillips

Slattery

2008

River Research & Apps

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An important aspect of river science and management is the identification of key boundaries, transition zones and hinge points. Such critical areas are likely to be important foci or indicators of the effects of environmental change on river systems. While geological controls on such features are widely recognized in upland streams, inherited or antecedent forms may also be important controls of key transitional points or reaches in alluvial coastal plain rivers. The critical zone of the lower Trinity River, Texas marks an important transition in river channel and valley forms, dominant processes and resulting geomorphological, hydrological and ecological characteristics. Its location is not a transient result of upstream or downstream propagation of effects. Rather, the location marks the contemporary upstream extent of the effects of Holocene sea-level rise, which in turn coincides with the point at which the Pleistocene upper Deweyville alluvial terrace surface is encountered. A more rapid rate of change and relatively sudden upstream displacement of this zone is likely when the upper Deweyville surface is flooded. Antecedent fluvial and alluvial topography inherited from previous aggradation, degradation and lateral migration episodes is likely to be an important control over modern fluvial forms and processes in other alluvial coastal plain rivers as well. Identification and mapping of such features may be extremely useful in pinpointing critical transition zones for water resource managers.

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“…Large fossil meander scars considered to be mid-Holocene in age (7.5 to 4.0 ka) along the Sabine River in southwest Louisiana provide evidence for substantially increased river flow and thus higher effective moisture compared with modern conditions. However, dating of the large meander features is uncertain, and they could be Pleistocene [36].…”

Section: Poore Et Al (In Press)mentioning

confidence: 99%

“…There are geomorphic features like the previously mentioned large fossil meander scars along the Sabine River in southwest Louisiana that indicate substantially increased river flow. However, uncertainty regarding the age of these large meander features [36] and other geomorphic features indicating increased river flow makes interpretation of the timing and duration of flood events problematic.…”

Section: Floods and Droughtsmentioning

confidence: 99%

Holocene Climate and Climate Variability of the Northern Gulf of Mexico and Adjacent Northern Gulf Coast: A Review

Poore¹

2008

Open Paleontol J

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Marine records from the northern Gulf of Mexico indicate that significant multidecadal-and century-scale variability was common during the Holocene. Mean annual sea-surface temperature (SST) during the last 1,400 years may have varied by 3 o C, and excursions to cold SST coincide with reductions in solar output. Broad trends in Holocene terrestrial climate and environmental change along the eastern portion of the northern Gulf Coast are evident from existing pollen records, but the high-frequency details of climate variability are not well known. Continuous and well-dated records of climate change and climate variability in the western portion of the northern Gulf Coast are essentially lacking.Information on Holocene floods, droughts, and storm frequency along the northern Gulf Coast is limited. Records of floods may be preserved in continental shelf sediments, but establishing continuity and chronologies for sedimentary sequences on the shelf presents challenges due to sediment remobilization and redeposition during storms. Studies of past storm deposits in coastal lakes and marshes show promise for constructing records of past storm frequency. A recent summary of sea-level history of the northern Gulf Coast indicates sea level was higher than modern sea level several times during the last few thousand years.

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Meander Scars as Evidence of Major Climate Change in Southwest Louisiana

Cited by 65 publications

References 15 publications

Channel adjustments of the lower Trinity River, Texas, downstream of Livingston Dam

Channel adjustments of the lower Trinity River, Texas, downstream of Livingston Dam

Antecedent alluvial morphology and sea‐level controls on form‐process transition zones in the lower Trinity river, Texas

Holocene Climate and Climate Variability of the Northern Gulf of Mexico and Adjacent Northern Gulf Coast: A Review

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