Sediment discharge from highway cut-slopes in the Lake Tahoe Basin, California, 1972-74
Streamflow and fluvial-sediment discharge data were collected at selected streams and highway gutters in the Lake Tahoe basin to determine the extent of erosion from highway cuts and to attempt to evaluate the effects of various land-treatment practices to reduce erosion. Estimate of long-term annual total-sediment discharge from six streams into the lake is 7,100 tons (6,400 tonnes), of which 2,300 tons (2,100 tonnes) is finer than 62 micrometres. During 1972-74, snowmelt runoff (April-July) accounted for 65 percent of the water and sediment discharge. Approximately 90 percent of the sediment is transported in suspension. Sediment measured at 16 gutterflow stations at the base of highway cut-slopes indicates that less than 100 tons (91 tonnes) of fine sediment per year are contributed to the lake from all California State highway cuts. Sediment-transport rates are highly variable, and an unknown part of the measured sediment was derived from sources other than highway cuts. Data were not adequate to demonstrate the effectiveness of treatments to stabilize cut-slopes.