The article explores how sediment supply affects the movement of sand in rivers and coastal areas. By studying physical models and field data, the researchers found that the amount of sediment on the bed influences how sand is transported. They also discovered that the speed at which sand dunes move depends on how the sediment is carried. The researchers developed a new formula that accurately predicts the movement of sand dunes when sediment supply is limited. This research helps us better understand how sediment availability impacts the shape and movement of underwater sand formations.