Wave Attenuation across an Intertidal Sand Flat: Implications for Mudflat Development

Abstract

Abstract On many tidal flats, there is a transition from sand flat at the more energetic seaward margin to mudflat further inland. However, the ability of sand flats to attenuate incident wave energy is an important but poorly understood constraint on mudflat development and morphology. This paper presents the results of an instrumented field study of incident wave attenuation across Roberts Bank, the sandy intertidal portion of the Fraser River Delta. The attenuation of wave height was monitored at four stations along a shore-normal transect for a period of 2 months (December 23, 2003, to February 10, 2004). The attenuation varied with the relative wave height ratio (Hs h−1) along the seaward margin, with dissipation increasing as water depths decrease and/or incident wave heights increase. Under the most dissipative conditions observed (Hs h−1 ≈ 0.25), the exponential decay coefficient reached 0.00045. This decay coefficient is an order of magnitude smaller than predicted by a simple wave transformation...