Overwash sand deposition can occur at all elevations in a salt marsh. The 

 depth of sand deposition was highly correlated with elevaiion at sites 1 and 3 

 during 1978. A series of high-velocity overwash surgej deposit sand toward 

 the fan terminus. Final surges of low velocity exhibit less penetration, and 

 deposition occurs closer to the barrier threshold (washover throat). 



The poststorm washover feature is a series of microterraces, composed of 

 steeply sloping foreset beds at the fan terminus. Reworking by tidal currents 

 subsequently redistributes the sand around the perimeter of the fan, destroy- 

 ing the terraced features. At Nauset Spit-Eastham, the greatest deposition 

 occurred on the road to the lee of the dune line. 



If a washover were to extend across the entire marsh to the bay, creating 

 a gently sloping planar feature, there would be a negative correlation between 

 burial depth and elevation. The greatest deposition would occur at low eleva- 

 tions. Deposition levels could be predicted from the slope and elevation of 

 the washover feature. 



Burial depth is a factor of storm conditions. Overwash surges that 

 reach the marsh or Day deposit greatest amounts of sand in low-lying areas; 

 smaller surges that dissipate their energy across the fan surface deposit 

 most of their sand at higher elevations (Fig. 55). Prior to the February 1978 

 storm, sand deposition on all washovers on Nauset Spit-Eastham had been posi- 

 tively correlated with elevation (case 1). Since the February 1978 storm, 

 sand deposition on most washovers is negatively correlated with elevation 

 (case II). 



Salt-marsh plant recovery from overwash is related to burial depth and 

 elevation. The data available for analysis from site 1 fan, an area repre- 

 sentative of washover case I, present a limited number of the possible 

 vegetative relationships between depth of burial, elevation, and recovery on 

 a barrier beach. The entire elevation range of Spavtina patens and Spa-retina 

 altevniflova is not present in the data. There is a good representation of 

 the elevation range in which both Spavtina patens and Spavtinr altevniflova 

 occur together. The upper elevation limit where Spavtina altevniflova grows 

 poorest is well represented. Neither the lower limit of the range of Spavtina 

 patens nor the lower limit of the range of Spavtina altevniflova is present 

 under conditions that allow plant recovery (i.e., burial exceeds limits of the 

 species) . 



While 134 quadrats in site 1 recovered from burial, this area represents 

 only some of the possible situations on a northeast barrier beach. Other 

 washovers on Nauset Spit-Eastham resemble site 1 fan (case I, Fig. 55), but 

 the majority of the washovers are broad, flat areas extending either far into 

 the low marsh zone or into the bay itself (case II). 



(a) Spavtina patens . The 538 quadrats sampled in 1977 that con- 

 tained Spavtina patens were buried by between 4 and 116 centimeters of wash- 

 over sand (Table 25). A total of 83 quadrats (15 percent) recovered from as 

 much as 33 centimeters of burial; 455 quadrats failed to recover from overwash 

 burial. All quadrats with Spavtina patens in site 3 were buried by more than 

 34 centimeters of sand; all quadrats in site 2, which continued to overwash 

 until July, did not recover. Using only those quadrats in site I that were 

 buried by less than 34 centimeters of sand (166 cases), 50 percent of the 

 quadrats (83 cases) with Spavtina patens recovered. 



105 



