Hamburg is a city in Fremont County, Iowa, United States, along the Nishnabotna River. The population was 1,240 at the 2000 census. Full breach at levee L-575 near Hamburg. jpg An aerial view of the breach at levee L-575 near Hamburg, which occurred June 13, 2011 and increased to nearly 300 feet in size. July 2011 Flooding Near Hamburg Iowa. jpg Natural-colour satellite image of muddy flood water near Hamburg after the levee breach.