barrier island status report - Coastal Protection and Restoration ...

Figure 29. East Timbalier Island Land Area Change Analysis (CEC, 2012)
4.4 Modern Delta Barrier Islands (Chenier Ronquille to Scofield Island)
The Modern Delta Barrier Islands have benefitted from a number of very recent barrier island
restoration projects, in addition to the Barrier Berms that were constructed as a part of the BP oil
spill response (Figure 30 and Table 5).
Although BICM did not report estimated disappearance rates for all of these islands, the BICM
data presented above through 2005 projected that Shell Island would have disappeared by 2029
(Table 2; Section 5.1). Recent assessment of shoreline erosion rates for the Modern Delta barrier
islands suggest that the recent projects constructed by CPRA have prograded the shoreline
positions gulfward relative to their pre- hurricanes Katrina and Rita positions (Figure 31).
Pre-restoration average rates of shoreline erosion ranged from -4.5 ft/yr (Pelican Island) to -41.7
ft/yr (East Grand Terre Island). Post-restoration rates of shoreline erosion range from +12.7 ft/yr
(Pelican Island) to +85.9 ft/yr (East Grand Terre Island) noting the higher value for East Grand
Terre Island may be related to the fact the project was recently completed in 2010 and the
analysis utilized the post-construction survey. For this same time period, the average erosion
rate for Chenier Ronquille was -46.1 ft/yr. It is noted that the post-restoration period included
the sand berms on Pelican and Scofield Islands, neither of which underwent full island
restoration during this time period. These reversals of shoreline change rates, from erosion to
accretion, are evidence that the restoration projects have benefited not only the individual
islands, but the system as a whole.
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