Burningham, H. and French, J. R., 2007. Morphodynamics and sedimentology of mixed-sediment inlets. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 710 – 715. Gold Coast, Australia, ISSN 0749.0208

Inlet research has a long history dominated by sandy systems: mixed sediment (sand-gravel) inlets have only recently been scientifically described, and as such remain an emerging research area. Inlet hydro- and morphodynamics are currently considered within the context of relative importance of wave and tidal processes, which is thought to account for geographical variation in their character and behaviour. Although wave-tide processes are principal forcing factors, sedimentological character is an important variable that can directly influence the efficacy of transporting mechanisms and the morphology of inlet shoals. Here, two sand-gravel inlets on the southeast coast of England are examined to evaluate the relative importance of sedimentology on inlet and ebb-tidal delta morphometry, and system behaviour. Woodbridge Haven at the mouth of the Deben estuary maintains a fixed inlet position 8 km to the south of Orford Haven, the more mobile mouth of the Alde/Ore estuary. Woodbridge Haven bypasses sediment through ebb-tidal breaching, whilst bypassing at Orford Haven occurs through a combination of long-term alongshore inlet migration and spit breaching with short-term ebb-tidal breaching. Both systems comprise sand and gravel sized sediment and are subject to a similar coastal climate (North Sea storm climate, meso-tidal regime). Whilst these inlets can be conceptualised in a similar way to their sand-dominated counterparts, their morphometry and periodicity are not directly comparable: they are smaller and bypass sediment more slowly than expected. This is thought to be a direct consequence of their sedimentological character.