y = .101x + .017, R-squared: .826 



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6 8 10 12 



Area of inundation peaks (mhrs) 



Figure 3. Regression analysis of total sediment deposited vs. area of inundation peaks. 



by the Corps. The regression on the 1987 data using high-tide elevation instead of inundation- 

 peak area produces an r 2 value of 0.77. This shows that variation in high-tide elevation explains 

 77% of the variation in total sediment deposited. 



In 1987, six tides reached elevations of over 0.8 m above datum, whereas none did during winter 

 1985, and only two reached such elevations during winter 1986. The modal high-tide elevation is 

 the same for all 3 years. The marsh surface floods at approximately 0.6 m above datum and Figure 

 4 shows that fewer tides flooded the marsh surface in 1986 than in either of the other years. 

 Although part of a frontal event in late March 1987 produced high tide, comparison with the 

 distribution of high-tide elevations for 1985 shows that this event was small in relation to the effect 

 of hurricanes (Figure 5). The maximum water level reached at Cocodrie during Hurricane Juan, 

 October 1985, was underestimated because the water level reached the table level of the tide gauge 

 and the float was unable to rise any higher for a period of several hours. 



Table 1 summarizes the results obtained from application of the model to winter 1985 and 1986 

 and calendar year 1985. These data indicate higher winter deposition during 1985 than 1986 

 associated with an increased frequency of overmarsh flooding and an increase in the magnitude of 

 the greatest inundation event, shown by the height of the high tide. However, comparison of these 

 figures for 5 months of the year with the results for a complete calendar year do not show, as 

 frequently suggested (Baumann 1980; Baumann et al. 1984; Cahoon and Turner 1987; Reed 1987), 

 that deposition in salt marshes primarily occurs during winter frontal passages. Initially, 1985 may 

 be thought to be an anomalous year that includes the effects of several hurricanes. However, 

 detailed examination of the figures shows that "hurricane tides," defined here as those reaching a 

 greater elevation than that of the highest cold front measured during 1987, contribute only 6.6% 



70 



