Revitalization of an Urban Stream in Terms of Water Quality and Recreational Usability: Assessment of Options through Hydrologic and Hydraulic Modeling

A stream called English Coulee with a catchment area of 347 km² passes through the city of Grand Forks in North Dakota before emptying into the Red River of the North. The coulee has a low head dam located in the upper basin area. Midway through the watershed, the coulee is routed into a diversion channel system with two entry points that bypass excess flood discharge around the city. The stretch of English Coulee that passes through the city has stagnation of flow, overgrowth of cattails, poor odor, and deposition of debris and generally poor water quality. A design project to restore the coulee was presented as a challenge to a group of students. The project adapted a hydraulic modeling approach which enabled gauging the effectiveness of multiple design options. The coulee basin’s hydrologic runoff and continuous inflow simulation were developed using HEC-HMS. HEC-RAS was used to model the hydraulic influence of the diversion channel, diversion intakes, weirs, bridges, culverts, and urban reaches. Pertinent survey data for existing control structures was collected. Simulations were carried out to evaluate the effectiveness of four design options consisting of structural controls and channel modifications. Modeling runs showed control modification as the more cost effective solution.