They form as sediment is brought to a lake or the ocean by streams and is deposited at the delta and cascades down the delta's front slope.
(They; form; as sediment is brought to a lake or the ocean by streams and is deposited at the delta and cascades down the delta's front slope) (sediment; is brought; to a lake or the ocean by streams) (sediment; is deposited; at the delta)
They sediment sediment
form is brought is deposited
as sediment is brought to a lake or the ocean by streams and is deposited at the delta and cascades down the delta's front slope
to a lake or the ocean by streams
at the delta