Effects of Tidal Stream Energy Extraction on Water Exchange and Transport Timescales

Abstract

Over the last decade, many studies have been conducted to estimate the upper limit of the theoretical resource of tidal stream energy and its associated influence on volume flux. However, studies aimed at evaluating the effects of tidal energy extraction on water exchange and transport timescale have been limited. This chapter provides a detailed review of different methods—from analytical methods to advanced three-dimensional numerical models—for quantifying the far-field environmental impacts of tidal stream energy extraction. Case studies from an idealized tidal channel–bay system and a realistic site in the Tacoma Narrows of Puget Sound, Washington State, USA, are given to illustrate the modeling approach for assessing the impacts of tidal stream energy extraction on flushing time using a three-dimensional numerical model. Model results indicated that the change in flushing time is approximately linearly proportional to the volume flux reduction when the relative change in volume flux is small. However, the rate of change in flushing time is several times greater than that of volume flux reduction. The present study demonstrates that flushing time can be used as a unique parameter for quantifying the environmental impacts of tidal stream energy extraction on water exchange in coastal waters.