Characteristics and Behavior of a Two-Hour Oscillation in the Buffalo River, Buffalo, New York

The Buffalo River discharges into Lake Erie near the upper end of the Niagara River. The lower 9.2 km of the river has been designated as a Great Lakes Area of Concern due to environmental problems associated with poor water quality, degraded riparian and river habitat, and contaminated sediments. The U.S. Army Corps of Engineers maintains a navigational channel at a depth of 6.7 m below mean lake level by periodic dredging. In 2011, extensive dredging took place within the upper portions of the river to remove some of the most contaminated sediments. This dredging resulted in both widening and deepening of the channel. The Buffalo River's gradient is low and current velocities generally are <10 cm/sec. The low flow conditions coupled with the orientation of the river allows Lake Erie waters to enter the Buffalo River reversing its flow. The largest episodic lake-driven flow reversals were found during strong westerly wind events that setup an elevated water level at the eastern (Buffalo) end of the lake. Lower amplitude flow reversals could also be associated with subsequent Lake Erie surface seiches or other phenomena. They also occur during times when no seiche conditions are present. The interaction between river flow and reverse (lake-driven) flow was investigated using Acoustic Doppler Current Profilers (ADCPs), temperature sensors, and water level recorders deployed for the past five years at various locations in the lower 9 km of the river. The collected data record the periodic reversals associated with Lake Erie seiches, but also reveal an oscillation within the river. This 'river seiche' has a period of ~2 hours and occurs continuously, persisting even during high flow events and during times of strong lake-driven flow reversals. To better understand the characteristics and behavior of this 'river oscillation', time-series plots and Fourier power spectra were produced from the ADCP data. These data show that the magnitude of the oscillation is on the order of 5-10 cm s-1. There are three coherent spectral peaks with significant power above the noise. These peaks have periods centered on 1.8, 2.0 and 2.2 hours. Our preliminary conjecture is that the oscillation is similar to a forced resonance in a closed basin.