Partial abstract: The purpose of this study is to define the reliability with which results of tests conducted in a physical model of the Delaware River Estuary can be used to predict the effects of modifications to the estuary. The Delaware River model at the Waterways Experiment Station was used to conduct tests to predict the effects of the navigation channel enlargement between Philadelphia and Trenton, and the results of the tests are compared with subsequent prototype data to determine the accuracy of the model predictions.