Bedform Association on a Ridge and Runnel Foreshore: Implications for the Hydrography of a Macrotidal Estuarine Beach
Keywords:Macrotidal beaches, ridges and runnels, sedimentary structures, foreshore processes, ripples/dunes, tidal currents, Solway Firth
The association of bedforms occurring on a macrotidal 'ridge and runnel' foreshore (Silloth beach, NW England) is investigated. The ripple forms and their orientations point to distinctive stages of wave-current interaction as the topography is submerged and subaerially exposed in a tidal cycle. The estuarine tendency of the coast creates additional flows corresponding to the incursion and excursion of tides. The widespread presence of bedforms which are not related to the wave-generated flows points to an integral role of tidal currents in the hydro-sedimentary dynamics of strongly tidal beaches. Remarkable changes occur in the bedform configurations under extremely windy conditions, mainly expressed by the development of dunes in the zones which are normally rippled. Such changes, though occasional, bring sedimentologically significant alterations in the beach dynamics. The study shows that important inferences can be drawn from bedform association of barred foreshores about the intertidal hydrography and possible sediment movement trends.