

80- 



60- 



40 



20- 



40 



Frequency 

 % Time 



/ '*> 



1 — I — I — r 



J F M A 



— I — r 



MONTHS 



-I — r 



A S 



1 — I — r 



O N D 



Figure 30. Seasonal salt marsh inundation 

 patterns (Baumann 1980). 



also varies. 



duration of 



October when 



During this 



inundated more 



water depth over the marsh 

 There is a sharp peak in 

 flooding in September and 

 water levels are highest, 

 time the salt marshes are 

 than 80 percent of the time 



Soil s 



As discussed in the previous section 

 on changes in an aging delta lobe, the 

 mineral content of marsh soil is directly 

 related to the hydraulic energy of the 

 system. In abandoned interdistributary 

 environments this means that sediment 

 delivery to the marsh decreases inland 

 coast (Units III, IV, I, and VI 

 26) and also into the marsh from 

 of local tidal streams (Figure 



frail the 

 in Figure 

 the edge 

 31). 



According to Baumann (1980), most of 

 the sediment is deposited during frequent 

 winter storms and rare summer tropical 

 disturbances, probably by redistribution 

 of sediment from bay bottoms (Figure 32). 

 As expected, the sediment size fraction 

 also varies with the hydraulic energy. 

 There is hardly any sand in delta marshes, 

 but the fraction of clays increases inland 

 with decreasing hydraulic energy 



(Gosselink et al . 1977). 



Rates of sediment 

 rather well known, both 

 (Cs) profiles and from 

 laid down on the surface 

 time (Hatton 1981, Table 



deposition are 

 from ^" Cesium 

 marker horizons 

 and tracked over 



8). Streams ide 



5 



o 



o 



< 



o 



<A 



5 10 15 20 



DISTANCE FROM TIDAL STREAM (m) 



5 



Figure 31. Variation in soil density and 

 soil carbon content with distance inland 

 from the stream edge in a salt marsh in 

 the Barataria basin (Buresh 1978). 



3. On 



2.5- 



2.0- 



2 1.5 



a 

 o 



< 1.0 



0.5- 



Streamside 

 Inland 



SEASONS 

 (1975-1978) 



W SU SP 



 



F 



SEASONS 

 (1975-1979) 



Figure 32. Sedimentation rates on the 

 Barataria saline marsh. (A) Mean seasonal 

 sedimentation 1975 - 78. (B) Mean 

 seasonal sedimentation 1975 - 79. 

 Sedimentation rates were highest during 

 the winders of 1975 - 78. Hurricane Bob 

 and tropical storm Claudette passed 

 through the area during the summer of 

 1979, resulting in very high desposition 

 rates (Baumann 1980). 



34 



