Overview

The USGS Patuxent Wildlife Research Center conducts extensive research on the evolution of tidal wetlands, considering biological productivity and physical forcings including sea-level rise and subsidence. An important component of tidal marsh evolution is sediment supply. At Blackwater National Wildlife Refuge, in Maryland, one marsh complex (BW) has undergone massive subsidence in the last century, while a nearby complex (FB) appears to be stable.Two field campaigns, in the spring and fall of 2011, aimed to quantify the sediment availability to these two distinctly different areas of Blackwater National Wildlife Refuge.  The rates of sediment flux to and from these complexes are unknown.

Marsh loss at Blackwater National Wildlife Refuge (U.S. Fish & Wildlife Service)

Measuring flows in the Blackwater River, the main conduit for sediment transport

Preliminary results

Preliminary results suggest that the BW complex, with a vast open-water area, is susceptible to wind-wave resuspension and ultimately sediment export. The FB complex, on the other hand, is near a large sediment source that may contain an estuarine turbidity maximum. This estuarine feature may be partially responsible for maintaining adjacent tidal marsh. The results demonstrate the temporal and spatial complexity of estuarine sediment transport and its potential effect on marsh sustainability.