A large delta has formed at the inlet of Bull Trout Lake (Sawtooth Mountains) since the last glaciation. This lake has no other lakes above it and consequently all of the sediment eroded from the watershed is deposited in its delta. In watersheds with multiple lakes, little sediment passes to the lower ones and they lack deltas.
The lake deltas are important processors of nutrients during flood periods, and they provide important habitat for a variety of organisms.
The lake in this photo is tinged light red from a rhodamine dye addition to measure hydrodynamic processes in the water column. Note the smooth slick extending far into the lake from the inflow of the stream (white sand area).