. The ecology of delta marshes of coastal Louisiana : a community profile. Marsh ecology -- Louisiana; Wetlands -- Louisiana. primarily taking place at the seaward ends of selected distributaries and that marshland loss was beginning to take place. By 1971 a large part of the crevasse system was being inundated by marine waters, and marsh loss was becoming significant. The only deposition was at the seaward ends of some of the distributaries and subaqueously in the bay fill front. Note that land loss begins first near the crevasse break. Here sedimentation is extremely slow, depending only on
. The ecology of delta marshes of coastal Louisiana : a community profile. Marsh ecology -- Louisiana; Wetlands -- Louisiana. primarily taking place at the seaward ends of selected distributaries and that marshland loss was beginning to take place. By 1971 a large part of the crevasse system was being inundated by marine waters, and marsh loss was becoming significant. The only deposition was at the seaward ends of some of the distributaries and subaqueously in the bay fill front. Note that land loss begins first near the crevasse break. Here sedimentation is extremely slow, depending only on overbank flooding, whereas higher sedimentation rates are still prevailing near the distal parts of the crevasse system. Figure 21 illustrates the crevasse growth and deterioration. Figure 22 shows on a single plot the cyclic nature of four of the Mississippi River crevasses; each cycle consisted of growth followed by deterioration. Projection of the present-day trends indicates a life cycle for a crevasse system that lasts 115 - 175 years. KO A CUBITS GAP Jt ' 175 /^\ ^M â 150 / '-\' 125 â ^' Volume *. p too /j \ / 75 50 25 â s. ai o 1 ⢠1 o 1 > 1 u 1 #' y J Arso . 0 ⢠l, » 4D 1 i OB o CD s 1900 1910 1920 1930 1940 1950 o % 10. Growth rates during progradation ranged from kmVyr to 2,7 kmVyr. Degradation rates averaged from to kmVyr. This growth and deterioration cycle of bay fills, although representing a relatively short time period, is similar to the cycle of major delta lobes de- scribed earlier. The delta cycle is on a much longer time scale - a growth period that approaches 800 - 1,000 years and a deterioration period that can be as long as 2,000 years. These bay fills provide an excellent model for evaluation of the future growth of the newly formed Atchafalaya Delta (Wells et al. 1982) and for the deterioration of the former Mississippi River delta lobes. The composite curve in Figure 22 shows a peak in the early 1940's, followed by a rapid lo
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