HISTORIC EVOLUTION OF A MARSH ISLAND - BLOODSWORTH ISLAND, MARYLAND

High rates of relative sea-level rise in the Chesapeake Bay of about 0 .3 m/century has caused rapid land loss of the Bay islands. This study is the first quantitative analysis of both perimeter and interior lan d loss for one of the large marsh islands-Bloodsworth Island. A geogra phical information system (GIS) was used for the analysis at a resolut ion of about 16 meters. From 1849 to 1992, the area of Bloodsworth Isl and declined by 579 ha, or 26% of the land area in 1849. The land loss can be divided into four geomorphic types: perimeter land loss, chann el widening, channel pending, and non-channel pending. Perimeter land loss is largest at 3.0 ha/yr from 1942 to 1992, but the three interior land loss types are also significant, totalling 1.6 ha/yr from 1942 t o 1992. Channel pending and widening were responsible for nearly all i nterior land loss prior to 1942. The initial formation of nonchannel p onds is attributed to a short-term acceleration in sea-level rise (to 7 mm/yr from 1930 to 1948). Subsequently, non-channel pending has been significant, particularly in the southeastern quadrant of the island. Compared to the mainland marshes, interior land loss has occurred at much slower rates; this is probably due to the low thickness of the ma rsh deposits on Bloodsworth. To date, bombing appears to have only had a secondary impact on land loss at the scale of this study. In the fu ture, the island appears increasingly vulnerable to interior break-up, particularly given another short-term acceleration of sea-level rise.