USING COLONIAL ERA SALT EVAPORATION PONDS AS A METRIC TO EVALUATE TIDE BASED MODELS OF SEA LEVEL CHANGE FOR THE PAST CENTURY

Located on the Atlantic seashore of Northampton County, Virginia, Mockhorn Island represents a marginal coastal setting that was utilized by early English colonists in the 17th century. The location of the island, the local euhaline salinity, and the low topographic elevation attracted early colonists to the area to build an evaporative salt works. The works consisted of many shallow ponds excavated within the upland ridges of the island. Because the infill channels were constructed as conduits for Spring tides and the ponds had to be shallow enough to promote effective evaporation, the basal pond elevation represents a proxy for late 17th century high tide levels. Thus, these shallow ponds, which currently have a depth range of -38 to -40 centimeters, provide a metric constraint for evaluating models of relative sea level change along the Atlantic seacoast since the late 17^th century. Using soil cores, in situ coastal-elevation survey markers, archival coastal survey field maps, and aerial imagery, this project is able to reconstruct the historic landscape, illustrate how anthropogenic features can be used as sea level index points, and show how colonial salt evaporation ponds can effectively evaluate tide-based models of sea level change for the past century.