Use of historical and geospatial data to guide the restoration of a Lake Erie coastal marsh

Historical and geospatial data were used to identify the relationships betw een water levels, wetland vegetation, littoral drift of sediments, and the condition of a protective barrier beach at Metzger Marsh, a coastal wetland in western Lake Erie, to enhance and guide a joint federal and state wetla nd restoration project. Eleven sets of large-scale aerial photographs datin g from 1940 through 1994 were interpreted to delineate major vegetation typ es and boundaries of the barrier beach. A geographic information system (GI S) was then used to digitize the data and calculate the vegetated area and length of barrier beach. Supplemented by paleoecological and sedimentologic al analyses, aerial photographic interpretation revealed that Metzger Marsh was once a drowned-river-mouth wetland dominated by sedges and protected b y a sand barrier beach. Extremely high water levels, storm events, and redu ction of sediments in the littoral drift contributed to the complete destru ction of the barrier beach in 1973 and prevented its recovery. The extent o f wetland vegetation, correlated to water levels and condition of the barri er beach, decreased from a high of 108 ha in 1940 to a low of 33 ha in 1994 . The lack of an adequate sediment supply and low probability of a period o f extremely low lake levels in the near future made natural reestablishment of the barrier beach and wetland vegetation unlikely. Therefore, the feder al and state managers chose to construct a dike to replace the protective b arrier beach. Recommendations stemming from this historical analysis, howev er, resulted in the incorporation of a water-control structure In the dike that will retain a hydrologic connection between wetland and lake. Manageme nt of the wetland will seek to mimic processes natural to the wetland type identified by this analysis.