Dune toe dynamics along the urbanised macro‐tidal coast of Belgium

Abstract

AbstractThe dynamics of the dune toe along the urbanised 65 km macro‐tidal coast of Belgium has been examined based on (bi‐)annual cross‐shore profiles derived from airborne LiDAR surveys conducted between 2000 and 2019. Results indicate that the average dune toe level is located at +5.9 m Tweede Algemene Waterpassing (TAW, Belgian Ordnance Datum), which is 1 m lower than the conventional dune toe level. However, this level is not static but rather increasing over time with an average rate of 2.3 cm/year, making it comparable with coastal areas along western Europe. Both landward retreat and seaward progradation of the dune toes are observed, with rates up to 2 m/year. The analysis revealed that dune growth is primarily facilitated by the development of incipient or embryonic dunes, new foredunes and modifications to the stoss slope of the original dune profile. Half of the sea‐fronting dunes were observed to be developed by brushwood fences, which had a positive effect on dune growth. At some locations, incipient dune development and shoreline progradation were observed seaward of old foredunes. Other dune regions were characterised by natural dune blowouts and management activities for recreational purposes. Dune toe reinforcements were implemented in the west to stabilise the dune toe and prevent erosion by waves. However, it was noted that if the adjacent beach accreted because of natural growth or periodic nourishment, incipient dunes could form in front of the reinforcement.