A Few Helpful Hints...

Contents of Erosion Control HELP
PART I hints
PART II hints
Miscellaneous Info...

PART I hints

The permissible shear stress and permissible velocity is calculated from the design storm, channel geometry (bottom width, side slope ratio), slope and roughness. Typical values of permissible shear and velocity are listed below. Those familiar with velocity and shear values will notice that in general the values are quite small. This is typical of erosion control materials.

Typical Permissible Shear and Velocities for Erosion Control Products

Duration	Shear range (psf)	Velocity range (ft/s)
Temporary (degradable)	0 - 2	0 - 7
Permanant (non-degradable)	0 - 5	0 - 10+

PART II hints

There are many inputs in this section. Channel designs are function of channel geometry, design storm (flow), slope, and roughness. Typical values of each one of these parameters are given in the tables below.

Typical Design Values

Design Parameter	Value
Design Storm	10 - 50 yrs
Design Flow (cfs)	10 - 100 cfs
Bottom Widths (ft)	2 - 10
Slope (ft/ft)	0.001 - 0.2

Typical Kb Values

Bend Serverity	Kb
Straight Reach (Rc/B > 9)	1.0
Mild Meanders (6 < Rc/B < 9)	1.1 - 1.4
Looping Meanders (2 < Rc/B <6)	1.5 - 1.9
Sharp Turns (1 < Rc/B < 2)	1.9 - 2.1

Note: Rc=radius of bend (ft); B=bottom width (ft)

Typical Manning's "n" Values

Material	Range of "n"
Bare, hard earth	0.020 - 0.030
Straw or Straw/Coconut Blankets	0.020 - 0.030
Excelsior Blankets	0.030 - 0.035
Jute	0.021 - 0.025
ECRM	0.025 - 0.030
TRM	0.030 - 0.035
Concrete	0.012 - 0.020
Revetment blocks	0.030 - 0.040
Riprap	0.040 - 0.100

Miscellaneous Info...

Many of you many be interested in knowing the exact classifications used in this server. Basically, all products where placed in categories based upon their performance characteristics (i.e. manufacturer provided permissible velocity and shear values). For a complete description, see the CLASSIFICATION page.

If you are interested in other erosion control products not listed in this server, a good source is the annual December issue of Geotechical Fabrics Report(the journal is commonly known as GFR). It lists specific products and index properties as well as manufacturer names, addresses, and contact persons.