Improved river forecasting techniques: a one-dimensional unsteady flow model for the Red River of the North

The 1997 flood of the Red River of the North illustrated the shortcomings of traditional empirical river routing and forecasting models in predicting river levels at flows and levels above those previously recorded. The Red River of the North is characterized by a low gradient which contributes to a variable loop rating curve at peak flows at specific gaged locations. As the river rose out of its banks, physical obstructions began to influence the discharge and stage at discrete locations. In the 1997 flood, nowhere was this more evident than in the communities of Grand Forks North Dakota and East Grand Forks Minnesota. Bridges, buildings and roadway embankments became obstructions to the river flow as the Red river breached the levees in the communities and continued rising to unprecedented levels. The National Weather Service is implementing a one-dimensional unsteady flow forecasting model, FLDWAV, for the Red River of the North to better account for the looped rating curve, the routing of water over the broad flat floodplain, the physical obstructions to the flow in the floodplain and for the obstruction of flow by bridges. Comparison of model calibration results with forecast hydrographs from the 1997 flood demonstrate the improved predictive capabilities of an unsteady flow model.