CREATION OF A SOUTHEASTERN UNITED STATES 

 SALT MARSH ON DREDGED MATERIAL 



Robert J. Reimold 



Coastal Resources Division 

 Georgia Department of Natural Resources 

 1200 Glynn Avenue 

 Brunswick, Georgia 31520 



THE SITE 



The Buttermilk Sound habitat devel- 

 opment site is located in the Atlantic 

 Intracoastal Waterway near the mouth of 

 the South Altamaha River, Glynn County, 

 Georgia (Figure 1). The site is a 2-ha 

 (5-acre) disposal area representing 5 to 

 7 yr of dredged material disposal. The 

 fringes of the area have already begun 

 to generate creekbank Spartina alterni- 

 flora marshes. 



Most of the area surrounding the 

 site is made up of tidal salt marshes 

 and small high ground hammocks, some of 

 which are remains of dredged material 

 disposal and rice farm diking. The soils 

 of the area have been mapped as wet al- 

 luvial land, tidal marsh, and "made 

 land." 



Daily tidal inundations cause the 

 surface layers of these marshes to build 

 up very slowly by deposition; there is 

 also a shifting of material caused by a 

 strong tidal current. These strong tid- 

 al currents create an average 2.1-m 

 (6.9-ft) tidal regime that floods the 

 marshes twice daily. 



The vegetation commonly found on 

 the tidal marshes adjacent to the habi- 

 tat development site is listed in Ta- 

 ble 1. Spartina alterniflora is the 

 most common species occurring on the 

 lower elevations of the tidal marsh. 

 Along the creekbanks where the tide 

 inundates the plants twice daily, S. 

 alterniflora grows to more than 2 m 77 

 ft] in height. When these plants die, 

 the dead material is readily swept into 

 the streams and nearby sounds where it 

 is broken down into detritus. 



In marshes of slightly higher ele- 

 vation, the common floral components 

 include Spartina cynosuroides , Juncus 

 roemerianus , Borrichia frutescens, and 



Scirpus robustus . The transition from 

 the marsh to the high ground is often 

 marked by a zone of herbaceous plants 

 such as Distichl is spicata , Spartina 

 patens , and Sporobolus virqinicus . Also 

 scattered throughout this area are the 

 shrubs Iva frutescens and Baccharis hal- 

 imifol ia . In the transitional zone 

 where the soil salinity is much higher, 

 grow specialized plants adapted to this 

 condition (e.g., Sal icornia virginica , 

 Sal icornia biglovii , Batis maritima , and 

 Limonium Nashii ). 



The dredged material island, si ight- 

 ly less than 2 ha (5 acres) along the 

 southeastern edge of the Atlantic Intra- 

 coastal Waterway, was used for the 

 habitat development site. The grossly 

 homogeneous sand substrate with an 

 elevation of 3 m (10 ft) above mean sea 

 level initially had very few resident 

 plant species. Table 2 lists the vegeta- 

 tion actually found on the site prior to 

 its grading and preparation for a habi- 

 tat development site. The areal cover- 

 age of this vegetation was less than 1% 

 of the total area. 



The substrate at the site prior to 

 habitat development consisted of 99% 

 quartz sand by weight and had no visible 

 stratification. Some variation in grain 

 size was noted, but the occurrence was 

 random and thus not documentable. The 

 limnic materials are indicative of the 

 high energy system caused by the flow of 

 the Altamaha River and the daily tidal 

 movements. The sand had a very low re- 

 sistance to deformation and rupture as 

 evidenced by its constant manipulation 

 resulting from current and wave action. 

 Table 3 presents the physical analysis 

 of cores taken from the development site 

 prior to habitat creation. 



Table 4 provides a summary of the 

 mineral content of the cores prior to 



