Maryland has experienced the rainiest year on record in more than a century, with the 43 inches falling through August 15 the most since 1889.So much stormwater has been flooding down the Susquehanna River into the northern end of the Chesapeake Bay that the Exelon Power company opened several of the flood gates on the Conowingo Dam, unleashing a torrent of sediment and pollution that had been trapped behind the dam.