Coastal dunes are important for protecting against floods and erosion. Existing models don't fully predict how dunes change over time. This study looked at how longshore transport affects dune and beach evolution over decades. By analyzing data from IJmuiden in the Netherlands and using a crossshore model, researchers found that longshore transport gradients play a big role in shaping dunes and beaches. The dune and beach respond differently to changes in sediment, and this study helps bridge the gap between nearshore, beach, and dune modeling.