Rivers and Streams, Characteristics - Hydro-Environmental Analysis: Freshwater Environments - page 21

1

1

1

1

1

1

2 1

2

1

2

3

1

2

1

3

1 4

3

1

1

2

1

2

1

1

4

1

FIGURE 2.7 Stream order classiication. (From FISRWG, Stream Corridor Restoration: Principles,
Processes, and Practices , Federal Interagency Stream Restoration Working Group, 1998.)

1,800,000 3,500

1,600,000

3,000

1,400,000

2,500

1,200,000

Number

2,000

1,000,000

800,000

1,500

600,000

1,000

Length

400,000

500

200,000

0

0

0 2 4 6

Stream order

8 10 12

FIGURE 2.8 Number and length of river channels of various sizes in the United States. (Based on data from
Leopold, L.B., Wolman, M.G., and Miller, J.P., Fluvial Processes in Geomorphology , W.H. Freeman, San
Francisco, CA, 1964.)

length increases, as the stream order increases (Figure 2.8). Similarly, the mean drainage area of the
contributing watershed increases nonlinearly with the stream order.
There are usually three to four times as many streams of Order n -1 as there are of Order n , each
of which is generally half as long and drains alittle more than one-ifth of the land area (Cushing
and Allan 2001). Most rivers and the great majority of river miles are in the lower order, which
should inluence how we manage our river systems.