Larger, heavier particles like pebbles and sand are deposited first, whilst the lighter silt and clay only settle if the water is almost still. The flow of water is strongest on the outside of river bends, eroding the bank, but is slowest on the inside of the bends, allowing deposition of sand and gravel.

Why do larger sediments get deposited first?

Water flowing over a steeper slope moves faster and causes more erosion. How water transports particles depends on their size. When water slows down, it starts depositing sediment. This process starts with the largest particles first.

Which deposits get carried the farthest?

When a stream begins to slow down the largest of particles will be left behind first. As the velocity becomes slower the next smallest size will deposit. The smallest particles will be carried the farthest.