Although they routinely 'sweep' for logs in the Dismal Swamp Canal, a fast moving stinkpot can 'relocate' the sunken logs so that you can get an occasional 'bump'.

This is not a problem for boats without saildrives; but, can and do present an occasional serious risk for those that do have saildrives. I went through in spring 2009 and 'aided' a sinking catamaran who struck a log with one of their saildrive .... USCG in Norfolk have large pumps.