Active Tectonics Impact on Society (1986) / Chapter Skim
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5. Alluvial River Response to Active Tectonics
5. Alluvial River Response to Active Tectonics
Pages 80-94
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From page 80... ...
Streams crossing the Monroe uplift in Louisiana and the Wiggins uplift in Mississippi show pattern, gradient, and depth changes that indicate that these uplifts are active. The Mississippi River shows effects of the Lake County and Monroe uplifts.
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From page 81... ...
In addition to these primary influences on channel and valley gradient and configuration, there will be secondary effects, as the rivers respond to the changed gradient (aggradation or degradation) , and there will be tertiary effects, as decreased or increased sediment loads influence reaches downstream of the deformed reach and as aggradation or degradation in the deformed reach progresses upstream.
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From page 82... ...
Smol I ~ Sed iment Size ~ Lorge Smoll ~ Sediment Lood ~ Lorge Low ~ Flow Velocity ~ High Low ~ Streom Power ~ High FIGURE 5.1 Channel classification based on pattern and type of sediment load with associated variables and relative stability indicated. From Schumm (1981)
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From page 83... ...
. The pattern change takes place at critical ranges of valley slope, stream power, and sediment load (Schumm and Khan, 1972~.
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From page 84... ...
The aggradation in zones B B and C reduced downstream sediment loads and induced degradation in zone D (Figure 5.4~. Adjustment of the meandering channel was as ex pected with increased overbank flooding upstream and an increase of sinuosity on the steeper reaches during uplift.
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From page 85... ...
The Lake County Uplift consists of part of four different geomorphic surfaces, the modern Mississippi meander belt and three separate Mississippi River braidedstream terraces. Lateral migration of the Mississippi River during and following the most active periods of deformation has eroded a considerable amount of the uplifted surface.
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From page 86... ...
_ .= _ ~ 'A ~ ,NORTH _, ,. No O ~ Flood Pbin -280 - 270 1 1 1 -Jo FIGURE 5.7 Longitudinal profiles between Mississippi [liver miles 845 to 930.
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From page 87... ...
The most severe caving occurred in the reach from the confluence of the Ohio and Mississippi Rivers to below Blytheville, Arkansas (Figure 5.8~. The increased sediment load caused excessive shoaling, enlargement of islands, and at some locations new islands and point bars were formed.
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From page 88... ...
Several streams Ouachita River, Bayou Bartholomew, Boeuf River, Big-Colewa Creek, Bayou Macon, and Deer Creek (Figure 5.10) that cross the Monroe Uplift in northeastern Louisiana and generally parallel the Mississippi River were studied by Burnett (1982~.
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From page 89... ...
To examine the variability of the channel-bed elevation and also changes in the bank height along the streams that cross the Monroe Uplift, channel thalweg elevations were plotted in relation to the valley distance along Boeuf River and Big Colewa Creek (Figure 5.13~. These projected channel profiles are not affected by changes in sinuosity because the thalweg elevation (or low water elevation)
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From page 90... ...
C 2.01 VALLEY DISTANCE FROM MOUTH (km) FIGURE 5.14 Effect of Monroe Uplift on Big Colewa Creek.
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From page 91... ...
. Mississippi River In the preceding discussion of the Mississippi River Valley, three areas of active tectonics have been identified, the Lake County Uplift, the Monroe Uplift, and the Wiggins Uplift.
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From page 92... ...
Note consistently high values of sinuosity in reaches affected by Lake County Uplift (Cairo, Illinois-Caruthersville, Missouri) ; Monroe Uplift (Greenville, Mississippi)
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From page 93... ...
(1970~. Quaternary geology of the lower Mississippi River Valley, Research Series No.
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From page 94... ...
Long-term changes of STANLEY A SCHUMM Lower Mississippi River meander geometry, in River Meandering, C
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