“Coastal defense” in many cases will mean dikes (a long wall or embankment built to prevent flooding), but softer approaches like artificial nourishment (meaning adding sand to beaches) can be even more effective in dealing with the impacts of rising sea levels and storm surges. In a 2019 overview of nineteen studies, dikes on average reduce damages by $40 for each dollar spent, whereas artificial nourishment can avoid $111 of damages for every dollar spent.
