IMIS - Marine Onderzoeksgroepen

For the optimal design of artificial dunes, a fundamental understanding of morphological changes throughout the early phases of dune growth is required. This study examines the effect of different vegetation densities and patterns on the subsequent dune development during the first three months following construction. Marram grass (0.40 m in height) was planted in six zones (20 × 20 m²) with three different densities (6, 9 and 15 plants/m²) and four different patterns (gridded, random, clustered, and staggered). Monthly drone surveys were combined with daily to weekly topographic RTK-GNSS surveys along 12 cross-shore profiles (two per zone). Beach wind conditions were continuously monitored with a meteorological station. Additionally, four aeolian sand transport measurements were conducted with Modified Wilson And Cook sand traps. Results demonstrate the importance of using a specific plant density as well as the use of spatial plant distribution. The use of a staggered or random plant distribution leads to the formation of narrower bedforms, while higher vegetation densities also result in narrower bedforms. Bedform height is greater in zones with high vegetation density. Regardless of plant density and distribution, each plantation zone experienced dune development with a volume of 6 m³/m, primarily influenced by the supply of aeolian sand from the adjacent beach. Aeolian sand transport rapidly decreases within a downwind distance of 20 m from the vegetation edge. The ability to trap sand varies between size of the plants, with wider plants being able to trap sand over shorter distances. By the end of the study period, nearly all vegetation zones were completely buried, causing sand to bypass the dune. The future progression of dune development will be determined by the interaction between vegetation growth and sand burial.