The invading species, in general, appeared to be the most widely 

 adapted of the typical salt marsh species. Common at both Drum Inlet 

 and Snow's Cut were the polychaetes Laeoneveis and Eetevomastus in the 

 creeks, and Dipteran larvae and Uoa pugilatov, the fiddler crab, in the 

 marsh itself. The polychaetes are deposit feeders; the others feed 

 mainly on the growth of algae and diatoms at the marsh surface. In time, 

 it is expected that these species will become less important as other less 

 common species invade, but that they will still be among the dominant 

 invertebrate fauna. 



V. SHORE PROTECTION AND SUBSTRATE STABILIZATION 



Stabilization was a major objective of the study, but one for which 

 we were unable to develop satisfactory evaluation procedures. The prob- 

 lem is the lack of unaffected or unbiased controls. For example, at the 

 Snow's Cut site, the original experimental plantings were divided into 

 three blocks, 45 to 60 meters wide, that extended roughly from the high 

 spring tide line, downslope to about MLW. These blocks were spaced 30 to 

 60 meters apart, leaving the intervening strips unplanted and undisturbed. 

 Dominant tidal currents are across the slope (parallel slope contours). 

 Erosion and deposition were monitored in two ways: (1) by cross-sectional 

 surveys started in 1971 through the planted blocks (Figs. 42 through 45) 

 and (2) by cross sections established in early 1972 through the unplanted 

 strips (Figs. 42 and 46 through 49). The latter might seem preferable 

 as controls, compared to following elevation changes of the planted blocks 

 over time. However, the protection afforded these unplanted areas by the 

 adjoining vegetated blocks affects the erosion, the deposition and the 

 revegetation occurring on them. Natural revegetation is gradually elimi- 

 nating these areas as "unvegetated controls." 



Even the provision of unplanted blocks or strips appears inadvisable 

 on eroding shorelines such as at Cedar Island since they would likely 

 promote erosion of adjacent areas. 



There appears to be no meaningful way to test stabilization effects 

 directly in small-plot field experiments. However, relative values between 

 variables based on vegetative growth may be sufficient at this stage. 

 Beyond that, wave tank tests might be the best approach. 



1. Snow ' s Cut . 



As indicated, certain cross sections were monitored at this site from 

 June 1971 (Figs. 43, 44, and 45) and others (Figs. 46 through 49) from 

 April 1972. All three planted blocks have shown a steady gain in elevation 

 over the 30-month period. The northernmost block (Figs. 42 and 43) has 

 trapped the most sediment, averaging close to 30 centimeters over the 

 entire slope with largest gains in about the upper half of the normal 

 tide range (Fig. 50) . It appears that more sediment may be coming from 

 the northern or upstream side and this planting may be intercepting 

 material and reducing the amount available to the areas downstream to it. 



90 



