Erosion Control Study Using Polyacrylamide (PAM)

and PAM+Gypsum on a Steep Slope

 

Dennis Flanagan, Kiran Chaudhari, Darrell Norton

 

 

 

Objectives:

 

PAM and PAM+Gypsum have been shown in previous studies (mostly on lower agricultural slopes) to improve infiltration, decrease runoff, and decrease soil loss.  The objectives of this study were to determine the effectiveness of PAM (P) and PAM+Gypsum (PG) in reducing runoff and soil loss on very steep slopes typical of construction sites, landfills, mines, etc.  Overall objectives of this study (in combination with 2 natural rainfall sites) were to examine the use of PAM and PAM+Gypsum as erosion control methods during critical period of vegetation establishment on plots, and determine their effect on both erosion control and grass establishment.

 

 

Treatments:

 

- Control

- PAM applied at 80 kg/ha in a liquid solution                   Estimated cost          $529/ha

- PAM applied at 80 kg/ha in a liquid solution                   Estimated cost          $579/ha

   plus Gypsum applied broadcast dry at 5 Mg/ha            

 

Site Characteristics:

 

Slope:  32%

Soil:  Silt loam topsoil over gravel subsoil

Plots:  3 m x 9 m,  3 replications

 

Rainfall Simulator Study in 1998:

 

Dry run:           64 mm/h  for  1 hour

Wet run:          64 mm/h  for  1 hour

Very wet run:

                        64 mm/hr  for 15 minutes

                        28 mm/hr  for 15 minutes

                        100 mm/hr for 15 minutes

 

Results:

 

PAM and PAM+Gypsum treatments significantly reduced sealing, runoff, and sediment loss.  Rill formation on the treated plots was virtually eliminated.

 

 


Erosion plots after very wet rainfall simulator runs in summer 1998 study, showing differences in surface condition and rilling between the treatments. Typical surface conditions following all rainfall applications are shown in this image.  Treatments from left to right are:  PAM+Gypsum, Control, and PAM.   Rills were painted orange for greater clarity.

 

 

 

Treatment

Total Runoff (mm)

%  reduction

Total Sediment Loss (Mg/ha)

% reduction

Dry Run

Control

41.5 a

 

76.3 a

 

 

PAM

5.9 b

85.7

1.0 b

98.7

 

PAM+Gypsum

4.7 b

88.6

0.7 b

99.1

 

 

 

 

 

 

All Runs Combined

Control

148.4 a

 

210.4 a

 

 

PAM

89.7 b

39.6

35.0 b

83.3

 

PAM+Gypsum

71.0 b

52.1

19.3 b

90.8

* Runoff rate and sediment loss mean values followed by same lower case letter are not significantly different at P<0.05 using t test for multiple means comparison.