In September 2012, we conducted a detailed survey of the physico-chemical and macrobenthic characteristics of a salt marsh created in the aftermath of the 2011 Great East Japan Earthquake in the Moune area of Kesen-numa City in Miyagi Prefecture. This study examined the newly created environments, with a special focus on their ecological development since the disaster. In the 18 months following the disaster, over 53 species of macrobenthos colonized the new aquatic environment. The majority of the dominant species were opportunistic. We detected marsh areas with high and low combinations of animal diversity and biomass. Animal distributions were strongly related to the current velocity of water flowing through a drainage pipe connecting the salt marsh with a river flowing alongside. High current velocities improved conditions for animal life by supplying feed items, such as phytoplankton and resuspended epipelic algae, and reduced the sediment organic content, thereby creating aerobic conditions. Water exchange between the salt marsh and Moune Bay was restricted to this one drainage pipe installed in the retaining banks of the adjacent river. Increased water exchange should improve environmental conditions, species diversity, and biomass.Special Issue（東日本大震災特集）