Flood frequency analysis



Accurate estimation of the magnitude of large floods and their frequency is of continuing concern to hydrologists, and thus a special session on this topic was held at the 1985 AGU Spring Meeting in Baltimore, Md. At the session, papers by W. Kirby and by K. Potter and J. Walker illustrated typical inaccuracies and likely errors in estimates of large Hood discharges by indirect methods. Kirby indicated that the standard error of flood discharges estimated by the slope-area method is likely to be at least 25%; possible scour and fill during the event are a major contributor to this error. Potter then presented detailed analyses illustrating probable errors of −5, +11, +17 and +44% in the estimation of large floods on four rivers in Wisconsin by indirect methods.