Marsh Graphic (IMAGE) University of Massachusetts Amherst Caption The arrival of the railroad and associated structures in 1850 along the banks of New York's Hudson River Tidal Estuary in several areas created the conditions for marshes to form. Credit courtesy of the Dams and Sediment in the Hudson project Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.