This report describes the application and results of an unsteady-flow model for the Milwaukee Harbor Estuary. The model simulates unsteady and upstream flow occurring in the estuary as a result of Lake Michigan Seiche. The discharge computed by the model indicates that upstream flow occurs throughout the estuary during periods of lake seiche. Flow conditions are extremely unsteady and major flow reversals may occur within 1 hr. The simulated discharge indicates that both upstream and downstream flows four times greater than the average daily discharge can occur during the same day. An estimate of 5- or 15-minute average discharge was required during selected runoff events and at various locations in the estuary as part of the Milwaukee Harbor Estuary study. The model provides a method to estimate 5-minute average discharges at selected cross sections in the estuary. The U.S. Geological Survey 's Branch Network Model was used to simulate stage and discharge. A finite difference computation scheme is used to solve the one-dimensional flow equations. Model input requirements include channel geometry data, discharge at the upstream tributaries, and stage data at the estuary mouth. The model was used to simulate the flow during six selected time periods in 1982-84 using a 5- or 15-minute computation interval. (Author 's abstract)