Rainfall, streamflow, sediment, and turbidity data were collected as part of a study to evaluate the effects of highway construction on suspended-sediment discharges in streams. The study was also designed to evaluate the effectiveness of different erosion-control measures in reducing sediment discharge. Although highway construction increased suspended-sediment discharges from two to four-fold, the rate of sediment discharge quickly returned to pre-construction levels when construction ended. The most effective sediment control evaluated was offstream ponds, which were designed to trap and store sediment laden water from the construction area. The offstream ponds trapped about 70 percent of the sediment that reached them during most storms. Seeding and mulching generally reduced sediment loads about 20 percent. Rock dams and bales reduced loads about 5 percent. An onstream pond, constructed on a large stream below the construction area, reduced sediment loads about 80 percent. However, unlike the offstream ponds, which stopped discharging runoff water soon after precipitation ended, the onstream pond kept discharging runoff water, and the stream below the pond remained turbid for extended periods.
