“The Fargo Project” located in Fargo, North Dakota, is an 18-acre stormwater detention basin that was retrofitted in 2015 to include an earthen-channel, sediment forebay, and various native vegetation within the floodplain and channels. Goals of this study were to assess how the post-retrofit earthen-channel performs relative to the pre-retrofit concrete-channel in terms of conveyance of small storms, and to estimate infiltration and evaporation from the post-retrofit detention basin during various storm sizes and intensities. Results showed that although channel roughness ultimately increased in the post-retrofit basin and allowed for greater instances of flooding for one channel, erosion of the main channel, with a larger urbanized contributing area, resulted in behavior similar to that of the pre-retrofit main channel for small storms. Modeled infiltration and evaporation showed total abstraction ranging between 2.9% and 11.7% of the maximum ponded volume for various storm sizes and intensities.