Knell's Island, part of the Charles E. Wheeler Wildlife Sanctuary, is located in the lower Housatonic estuary in Long Island Sound. Field studies over a 2-year period indicate that large segments of this high marsh habitat are eroding at rates as high as 1 meter per year. Knell's Island and the surrounding salt marsh are unique among the wetlands of coastal Connecticut in that they have undergone extremely rapid growth over the last 100 years. Since the late 1800's, Knell's Island has sustained a meter of vertical accretion and has expanded laterally from approximately 17,000 square meters to its present size of 52,000 square meters. Present day erosion patterns signal a drastic alteration of this unusual growth regime. Several suspect mechanisms are being investigated. These include current shear, ice abrasion, bio-erosion by burrowing fiddler crabs and boat wakes. Preliminary results indicate that crab burrow density does not correlate well with erosion rates but appears to play an important role in erosional style. Although data is still being collected, the interaction of currents and boat wakes appears to be a likely mechanism. Short-term erosion rates are being monitored by yearly field surveys. The erosional history of the island is being investigated using aerial photographs and historical maps.