Sediment concentration and turbidity changes during culvert removals.
Authors:
Foltz, R.B. Yanosek, K.A. Brown, T.M. USDA, FS
Source:
Journal of environmental management. 2008 May, v. 87, issue 3, p. 329-340.
NALT Subjects:
national forests roads drain pipes streams water quality soil erosion sediments sediment yield turbidity Idaho Washington
Issue Date:
May-2008
Abstract:
The concentrations of sediment and turbidity in stream water were monitored during culvert removals to determine the short term effects of road obliteration. Sediment concentration was measured at 11 stream crossings among two locations in Idaho and one in Washington. Sediment concentration immediately below the culvert outlet exceeded levels above the culvert outlet by at least three orders of magnitude at all stream crossings. Sediment yields ranged from 170 to less than 1 kg in the 24-h period following culvert removal. Turbidity exceeded the regulatory limits during culvert removal at all locations monitored in this study and remained above the limits beyond the monitoring periods of 24 h at four of the locations. Sediment concentrations 100m downstream of the culvert outlet were reduced by an order of magnitude, but did not change the turbidity values sufficiently to meet regulatory limits. Sediment concentrations an average of 810m downstream of the culvert outlet were similar to sediment concentrations above the culvert for the entire excavation period and turbidity regulations were met. Mitigation consisting of two straw bales placed in the stream caused a significant reduction in sediment yield from an average of 67 kg to an average of 1.6 kg. r 2007 Elsevier Ltd. All rights reserved.
