Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2003
Publication Date: 8/31/2003
Citation: Peterson, J.R., Flanagan, D.C., Robinston, K.M. Channel evolution and erosion in PAM-treated and untreated experimental waterways. Transactions of the American Society of Agricultural Engineers. 2003. v. 46. p. 1023-1031. Interpretive Summary: Large flows of water in fields and channels can cause serious erosion problems. A typical conservation practice is often to plant grass or other plants in the areas where water flows, because the vegetation and its root system help to hold the soil in place. However, the process of initially getting grass to grow properly in an earthen channel is difficult and can be hampered by large rainstorms and erosive runoff flows. This paper describes the use of a chemical soil amendment called PAM to protect and hold the soil in place in concentrated flow channels, possibly while trying to get permanent vegetation to grow. The experiment conducted here showed that the PAM treatment could virtually eliminate soil detachment in a channel similar to one in a farmer's field, with water flows up to 200 gallons per minute. This work impacts conservationists, engineers, and farmers involved with construction of grass waterways or other earthen channels. Successful utilization of PAM could potentially improve grass waterway establishment and decrease installation costs. More research needs to be done to see if using less of the PAM would still be as effective, as well as if the material might be used in emergency situations related to earthen dam overtopping.
Technical Abstract: Unprotected earthen waterways (e.g., grassed waterways before vegetation) and ephemeral gullies are prone to severe erosion. Previous research has suggested that polyacrylamide (PAM) may reduce erosion in areas of concentrated flow. This research tested the hypothesis that a PAM-treated channel would result in significantly less erosion than untreated soil in a pre-formed, trapezoidal channel. Channel geometry and sediment concentration were measured for each of four inflow rates (0.0016, 0.0032, 0.0063, and 0.0126 m3·s-1). A secondary objective was to measure the influence of PAM on headcut rate advance. Measured sediment yield rate was significantly less from PAM-treated channels than from the control. Reductions in sediment yield rate ranged from 93 to 98%. Channel incision depth was not different between the two treatments; however, effective flow widths (assuming rectangular channel geometry) were significantly greater for the untreated control channel. Headcut advance rates were greatly reduced in PAM-treated channels (0.06 to 0.6 m·h-1) compared to the untreated channel (17.8 m·h-1) in our limited data. These results show that PAM can be a very effective means of controlling erosion in a channel or gully subject to high-volume concentrated flows.