. The ecology of delta marshes of coastal Louisiana : a community profile. Marsh ecology -- Louisiana; Wetlands -- Louisiana. 1800 1820 1840 1860 1880 1900 Date 1920 1940 1960 1980 Figure 22. Composite subaerial growth curve, Mississippi River subdeltas. Total subaerial land determined from averages at 10-yr internals (Wells et al, 1982). "greenhouse" effect that is wanning the earth's surface and melting the polar ice caps. The net affect of both true sea- level rise and coastal subsidence has been a change in the coastal submergence rate from about cm/yr during 1948 to 1959, t
. The ecology of delta marshes of coastal Louisiana : a community profile. Marsh ecology -- Louisiana; Wetlands -- Louisiana. 1800 1820 1840 1860 1880 1900 Date 1920 1940 1960 1980 Figure 22. Composite subaerial growth curve, Mississippi River subdeltas. Total subaerial land determined from averages at 10-yr internals (Wells et al, 1982). "greenhouse" effect that is wanning the earth's surface and melting the polar ice caps. The net affect of both true sea- level rise and coastal subsidence has been a change in the coastal submergence rate from about cm/yr during 1948 to 1959, to nearly on/yr between 1959 and 1971. Although these data are for a gauge at 1 25- 1 0- 0-5 Years spanned by estimate Midpoint Reference 1 Adams et at 1976 20ozier 1983 3Gaqliano f. Van Beck 1970. 1 940 YEAR Figure 23. The accelerating wetland loss rate in the Mississippi Delta (based on data from Dozier 1983). Bayou Rigaud in the Barataria basin, the trend is similar along the whole Louisiana coast (Gosselink et al. 1979). In order to remain at intertidal elevations marshes must accrete vertically as rapidly as they are sinking. The rapid rate of marsh degradation indicates that they are not doing so, an observation supported by recent research (Delaune et al. 1983). One reason is that the Mississippi River no longer supplies as much sediment to the coast as it has historically. Keown et al. (1980) reported that sediment supplies are only about 60 percent of what they used to be, despite the presumed increase in erosion that accompanies forest clearing on the upper watershed. The reduction is presumably due to the construction of dams on the upper reaches of the river and its tributaries. The dams also remove the coarser sediments selectively, so that the sediments reaching the coast are depleted of the sand that is the main foundation material for delta growth. This means that the river can no longer support as 24. Please note that these images are extracted from scan
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Keywords: ., bookcentury1900, bookcollectionbio, booksubjectwetlandslouisiana
