Introduction to Stream Restoration - Hydro-Environmental Analysis: Freshwater Environments - page 230

(a) Closed diamond pattern (b) Open diamond pattern

Patterns may be repeated
in a section

Groups of
rocks

Single rocks at
random

(c) Large rocks in a bend

FIGURE 8.16 Placement of rocks. (Modiied from Barton, J.R. and Cron, F.W., Restoration of Fish Habitat
in Relocated Streams , U.S. Department of Transportation, Federal Highway Administration, Washington,
DC, 1979.)

Boulders are typically placed randomly or in clusters and the recommended boulder size is
a function of the stream hydraulic characteristics and the equipment available (Figure 8.16).
Generally, in larger streams, a minimum diameter of 2 ft. is recommended, while smaller boulders
may be appropriate in smaller streams (see Table 8.4).

8.4.5 c LeanInG (t raSH r eMoVaL )
One common problem for degraded streams is that they often serve as illegal dumping sites for
trash, from depositing grass clippings or debris from yards to household garbage and appliances,
impacting not only the stream's characteristics, but also its aesthetics and recreational value. The
removal of trash from streams and rivers is a common restoration practice. It is also a restoration
practice that can usually beneit from public involvement and education, such as in Adopt-A-Stream
projects. The public may be involved in trash removal and/or monitoring. For example, the Friends
of the Rappahannock hosts annual spring and fall cleanups, in which typically over 300 individuals

TABLE 8.4
Approximate Basis for Selecting Large Rocks

Channel Width at
Normal Summer Flow

Depth of Water Where
Rock is Placed

Dimension of Long Side
of Rock

Up to 20 ft (6 m) 1.0-2.5 ft (0.3-0.75 m) 2-4 ft (0.6-1.2 m)

20-40 ft (6-12 m) 1.0-3.0 ft (0.3-0.9 m) 3-8 ft (0.9-2.4 m)

40-60 ft (12-18 m) 1.5-4.0 ft (0.45-1.2 m) 4-12 ft (0.6-3.6 m)

5 ft (1.5 m) to as large as
can be handled with
available equipment

Above 60 ft (18 m) 1.5-5.0 ft (0.45-1.5 m)

Source: Barton, J.R. and Cron, F.W., Restoration of Fish Habitat in Relocated
Streams , U.S. Department of Transportation, Federal Highway
Administration, Washington, DC, 1979.