Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2002
Publication Date: 10/31/2002
Citation: Flanagan, D.C., Chaudhari, K., Norton, L.D. Polyacrylamide soil amendment effects on runoff and sediment yield on steepslopes I: Simulation rainfall conditions. Transactions of the American Society of Agricultural Engineers. 2002. v. 45(5). p. 1327-1337. Interpretive Summary: Soil erosion on steep slopes can cause large erosion problems that are expensive to repair. On many types of construction projects such as highway embankments, design procedures dictate that slopes as steep as 50% (2:1) be used due to the need to fit the project into a relatively small area. Soil can easily be lost on these embankments because the land is usually disturbed and loose, there is little natural protective cover, and erosive rainfall and runoff can detach and rill the soil. The experiment described in this paper used a chemical called polyacrylamide or PAM sprayed on the soil surface to try and reduce the runoff and soil loss on a steep 32% slope. Another chemical called gypsum, which is sometimes used as a fertilizer, was also applied in combination with the PAM. A machine called a rainfall simulator was used to apply a range of rainfall rates to a constructed embankment, then the runoff and soil loss that occurred was collected from plots beneath the rainfall simulator. The study found that PAM and PAM with the gypsum were very effective at reducing runoff (up to 89%) and soil loss (up to 99%) under the extreme storm conditions used. The use of these types of chemicals on steep slopes could help to greatly reduce soil loss during critical periods at construction sites when soils are bare. This research impacts control of soil erosion and sediment loss from steep slopes, providing an alternative approach for control that is cheaper than other conventional methods.
Technical Abstract: Runoff and soil erosion from disturbed soil on steep slopes can be especially severe due to loose soil conditions, lack of plants or residue materials, and the potential for highly erosive rainfall and runoff. Efforts are usually made to create permanent vegetative cover as quickly as possible; however, large rainfall events during critical periods of vegetation establishment can often cause extensive soil loss. Sediment generated from erosion can impair off-site water quality, and on-site damages to the eroded region can be so extensive that expensive regrading earthmoving, reseeding, and remulching may be necessary. This paper reports on the effectiveness of using two types of soil amendments to reduce runoff and soil loss from a silt loam topsoil placed on a constructed 32% slope. The three treatments used were a control, an application of 80 kg/ha anionic polyacrylamide (PAM) as a liquid spray, and an application of 80 kg/ha PAM as a liquid spray combined with a dry granular application of 5 Mg/ha of gypsum. Replicated plots were subjected to a range of rainfall intensities under a programmable rainfall simulator, and resulting runoff and sediment loss measured. In the first event of 69 mm/h uniform rainfall applied over one hour to initially dry soil, the PAM and PAM with gypsum treatments significantly reduced runoff by almost 90% and sediment yield by 99%, compared to the control. Total runoff through a series of simulated rainfall events was reduced by 40 to 52%, and sediment loss was reduced by 83 to 91% for the plots treated with PAM and PAM plus gypsum, respectively. These results indicate that the use of PAM alone or in combination with gypsum can significantly reduce runoff and soil loss from large storm events.