| This study documents (1) the timing of hydraulic mining sediment production, (2) the volume and character of deposits, (3) channel responses during and after the influx of sediment, and (4) sustained reworking of the sediment more than 100 years after its introduction.;Hydraulic gold mining began in the Bear River basin in 1853. Mining sediment began to reach main channels in 1862. Sediment production decreased in the late 1860's, increased again during the 1870's, but decreased suddenly when unrestrained mining was enjoined in 1884. Sediment production in the Bear Basin during this period was more voluminous than assumed previously, as was storage. Mining was renewed on a small scale after 1890, but produced less than 2% of the total mining sediment produced in the basin. Deposits from this later period influenced local channel morphology, however, and terraces graded to some of the small sediment detention dams remained in 1985.;Mining sediment is easily discriminated from non-mining sediment, because it is distinctly quartzose in composition and has well-sorted, fine-grained textures. An index for identifying mining sediment and determining mixing ratios is presented. Much mining sediment remains stored in terrace deposits and beneath the channel bed.;Continued erosion, transport, and deposition of mining sediment in the Bear River indicate that episodic deliveries of sediment may have long-lasting effects; much longer than predicted by previous investigations based on other Sierran streams. Mining sediment still dominates the upper Bear channel and moderate-magnitude floods are competent to move the fine-grained channel bedload.;Streamflow measurement data at three cableways reveal 20... |
