channels (particularly in larger rivers) are needed and can only be developed on the basis of

studies with a far broader scope than the normal project-oriented work funded by developers.

Over the last several years, numerous agencies and practitioners have published guidelines for

stream corridor restoration and channel rehabilitation design. For example, in 1998, fifteen

Federal agencies and partners published a manual, Stream Corridor Restoration - Principles,

Processes and Practices (Federal Interagency Stream Restoration Working Group 1998). This

document represents a cooperative effort by the participating agencies to produce a common

technical reference on stream corridor restoration. Recognizing that no two stream corridors

and no two restoration initiatives are identical, this technical document broadly addresses the

elements of restoration that apply in the majority of situations encountered. Reference is also

suggested to Rosgen (1996) and U.S. Army Corps of Engineers publications such as Watson

et al. 1999. HEC-20 (Lagasse et al. 2001) provides an introduction to stream restoration

concepts and HEC-23 (Lagasse et al. 2001) presents guidelines and references for

bioengineering bank protection treatments.

^

Downslope flow over a plane bed inclined at an angle θ shown in Figure 6.32 is equivalent to

^

an oblique flow on a side slope with θ = θ and λ = 90. Then, according to Equation 6.4, β = 0,

and from Equation 6.6,

1 + sin 90 + 0

η′ = η

=η

2

It follows from Equation 6.3 that the stability factor is

^

cos θ tan φ

S.F. =

^

η tan φ + sin θ

Alternatively, solving for η yields

^

θ

^ 1 - tan

η = cos θ

φ

S.F. tan

Using this information we wish to calculate (if the angle of repose, φ = 40), what is the

^

maximum bed angle θ at which η will be 5 percent different from that of a horizontal bed.

^

^

Solving for θ with η = 0.95, S.F. = 1 and φ = 40 yields θ = 2.35 or 4.1 percent.

6.55

Integrated Publishing, Inc. |