The sedimentary processes of the Ganghwa tidal flat has been changed over 20 years because of the
large-scale construction projects. The sedimentary environment of the Donggum tidal flat, located in the eastern part
of Ganghwa tidal flat and in the lower reaches of Yeomha channel, was affected by changes the tidal current
regime and estuarine circulation. These resulted an occurrence of rapid deposition in the tidal flat. The silt-clay
laminated silt facies in the upper parts of two core sediments suggested that deposition had been relatively high in
the tidal flat. The sedimentation rates from the cores using 210Pb analysis were 3.25cm/year(st. 3) and
3.47cm/year(st. 5). However the short-term sediment accumulation rates from 2010 to 2012 were mostly less than
1cm/year, indicated that the sediments deposited relatively low rates. As a result, the sediment in the Donggum tidal
flat rapidly accumulated during 2000s due to constructions of man-made structures. Recently, the increase of
elevation in the tidal flat resulted to show relatively low sedimentation rate with seasonal variations.