velocity of the stream’s flow and causes the stream to drop off much of its load. The farmers
who use the floodplain areas around the Nile River rely on these deposits to supply nutrients
to their fields each year as the river floods its banks. At flood stage, a river will also build
natural leveesas the largest size particles build a higher area around the edges of the
stream channel (Figure10.5).
Figure 10.5: After many floods, a stream builds natural levees along its banks. ( 11 )When a river meets either standing water or nearly flat lying ground, it will deposit its load.
If this happens in water, a river may form adelta. From its headwaters in the mountains,
along a journey of many kilometers, rivers carry the eroded materials that form their stream
load. Suddenly the river slows down tremendously in velocity, and drops the tremendous
load of sediments it has been carrying. Deltas are relatively flat topped, often triangular
shaped deposits of sediments that form where a large river meets the ocean. The name delta
comes from the capital Greek letter delta, which is a triangle, even though not all deltas
have this shape. A triangular shaped delta forms as the main stream channel splits into
many smallerdistributaries. As the channel shifts back and forth dropping off sediments
and moving to a new channel location a wide triangular deposit forms.
There are three types of beds that make up a delta (Figure10.6). The first particles to