peak of record for 6 U.S. Geological Survey (USGS) streamflow-gaging stations on the Potomac River and 10 streamflow-gaging stations on selected tributaries to the Potomac River. Peak discharge, peak gage height, the date and time of the peak, and approximate recurrence interval are presented for each flood event at these streamflow-gaging stations. Data compiled from selected high-flow discharge measurements at the six Potomac River streamflow-gaging stations are presented. The gage height, top width, cross-sectional area, mean velocity, maximum velocity, and discharge are presented for each selected discharge measurement. Any corresponding discharge on the C & O Canal that was measured or estimated during these discharge measurements is presented. Ranges of Manning's roughness coefficient were computed for the range of selected discharge measurements based on estimates of water-surface slope or the channel-bed slope. An inventory of selected flood studies and reports, and additional USGS data collected along the Potomac River and the C & O Canal NHP also are presented. Included are (1) a listing of selected flood studies and reports, and (2) a listing of USGS indirect flooddischarge measurements that have been made at the six Potomac River streamflow-gaging stations in the vicinity of the C & O Canal NHP. Information on historical streamflowgaging station records and discharge measurements on the C & O Canal also is presented.