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ARS Home » Research » Publications at this Location » Publication #99288


item Bonta, James - Jim

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Studies are lacking on the effects of mining and reclamation on suspended sediment concentrations and loads from small watersheds, and are needed for mine permitting, model validation, and regulation development, among other needs. Such an investigation on three small experimental watersheds documented the drastic increase in concentrations and loads due to mining and reclamation disturbances, and their drastic decreases after the watersheds were reclaimed. Concentrations and loads can decrease to below or near undisturbed watershed levels with a good reclamation practice, in spite of higher stream flows that occur after a watershed is reclaimed. Diversions placed on land surfaces for erosion control are useful for helping vegetation to become established, but can cause elevated sediment concentrations and loads if not installed and maintained properly. This study will be useful for science-based regulation development and waivers from regulations, and for further research on sediment-yield modeling in surface mines. Results documented in this study will be useful to Federal and State regulators, mine operators, scientists, consultants, and university personnel.

Technical Abstract: Three small, experimental watersheds in Ohio, with differing lithologies and soils, were monitored for runoff and suspended sediment concentrations during different phases of watershed disturbances and from the undisturbed watershed condition, through post coal mining and watershed-reclamation activities. The profound increase in suspended-sediment concentrations, load rates, and loads due to mining and reclamation activities, and the subsequent drastic decreases after reclamation, were documented. Probable watershed runoff areas were difficult to quantify due to rapid daily surface disturbances. Maximum concentrations and load rates occur during times of active disturbances that expose loose soil and spoil to potentially high-intensity rains. The straw-crimping reclamation technique is very effective in reducing sediment concentrations, load rates, and loads after reclamation to below the undisturbed watershed concentrations. Data suggest that diversions can cause sediment concentrations to remain a an elevated level compared with the undisturbed watershed because diversions were not well maintained and overtopped, and water can be concentrated to a rock chute that is easily eroded to a gully, even after gully repair. Diversions appear to be useful for vegetation establishment, but should be maintained properly during this time, and then removed for final reclamation after good vegetative cover is established. Reductions in suspended-sediment concentrations and load rates to below or near undisturbed-watershed levels is possible, in spite of higher average sampled flows and documented increases in runoff potential through the watershed curve number.