From report of the City Class union gunboats like the Mound City and DeKalb, those gunboats had a draft of about 6 feet. During the Battle of St. Charles those Gunboats almost became stranded by the falling water levels on the White River and that is one of the reasons that Geneal Curtis did not recieved the supplies he needed and have to redraw to Helena. That is also the reason that the CSS Ponchartrain was never in the White River at the time of the St Charles battle as some historians suggest because of Dunnington's reports of the action. The Ponchartrain drew 11 feet of water needed to navigate. That is the reason she was pretty well landlocked at Little Rock most of the time.