 The construction of Benning and other bridges and the diversion of inflowing streams to agricultural use also slowed the river's current, allowing much of the silt to settle and be deposited.Between 1860 and the late 1880s, large mudflats ("the Anacostia flats") formed on both banks of the Anacostia River due to this deforestation and runoff.At this time, the city allowed its sewage to pour untreated into the Anacostia.