A short distance downstream of the Stillwater Dam, the Lackawanna River flows through the Lackawanna River Gap and passes by the Stillwater Cliffs. Numerous other gaps, such as the Leggetts Creek Gap, Cobbs Gap, the Rushbrook Gap, and the Fall Brook Gap, occur on tributaries of the river. Downstream of Scranton, the river's channel becomes broader and the river becomes shallower. Assorted waste and debris is piled in many places in the Lackawanna River watershed. The waste can sometimes block waterways, causing localized flooding. During storms, minor tributaries also wash large quantities of urban debris and coal waste into the river, degrading it further.