Seagrass berm deposition on a Mediterranean embayed beach

• Seagrass berm deposition on a Mediterranean beach was inferred using video monitoring.
• Depositional/erosional cycles of seagrass berm occurred from October to April.
• Litter floating in the inner surf zone can be redeposed several times on the beach.
• Litter can be relevant on the formation of the berm on sheltered beaches.

Seagrass leaf litter is commonly found along shores all around the world. The Mediterranean Sea is not an exception, and along the sandy shore wide and thick deposits of leaf litter can be found. The deposition of these structures has not yet been studied, our aim is to clarify the depositional–erosive process of seagrass leaf litter on a Mediterranean beach. A video image system, consisting of a camera and a video camera, was used to investigate the dynamics of the deposition of seagrass litter on beaches. Time-exposure images proved useful in investigating the seagrass berm deposition over the monitored period by using the EOF analysis, while videos are used to describe every deposition and erosion cycle.The deposition of seagrass berms occurred from late October to early April, while during the rest of the year, the beach was free of litter. The first deposition occurred in October, when seagrass litter was available on the submerged bay domain, the seagrass berm erosion occurred after several peaks of wind speed, while the deposition started when the wind speed increases and the waves start to break near to the shoreline. The deposition of the leaf litter on the beach starts as a strandline at the landward edge of the wave action and proceeds seaward up to the shoreline. Litter residue, eroded away by the waves and floating in the inner surf zone can be redeposited in little patches at the end of an erosion cycle. In conclusion, leaf litter may be relevant to berm formation and litter floating in the inner surf zone and in the lower swash zone is part of the materials exchanged between submerged and emerged beach.