Project Number: 6408-13000-012-32
Project Type: Reimbursable

Start Date: May 01, 2004
End Date: Oct 30, 2005

Objective:
To determine rates and volumes of fine-sediment transport to Lake Tahoe from stream-channel erosion.

Approach:
Estimate the contribution of sediment loaded to Lake Tahoe from all 63 watersheds resulting from stream channel erosion using the (a) results from individually modeled streams and calculated loadings contained in the recent National Sedimentation Laboratory report on stream channel erosion at Lake Tahoe, (b) the existing LTIMP stream water-quality database, and (c) flow estimates from ungaged streams. Values should be expressed in terms of actual load at the stream mouth (kg/yr) and percent of total sediment load. Where data is insufficient, estimates of the expected percent of total load should be provided. Given the sensitivity of water clarity to particles in the size range of 0.5-30 µm, emphasis should be placed on this category. To the extent possible, also estimate the number of particles entering the lake through stream channel erosion using mass and expected density values for each size range. Calculate and graphically show the levels of uncertainty associated with calculations/estimates of load at the individual stream level, quadrant level and basin-wide level. Consult with Lake Tahoe modelers to best integrate findings on sediment contributions from channels into their ongoing efforts. Conduct (1) rapid geomorphic assessments and boundary-material sampling at un-sampled stream mouths to augment the existing database and (2) survey of two reaches of the Upper Truckee River for use in a feasibility evaluation of effective best-management practices (BMP) associated with channel stability. Conduct a preliminary feasibility evaluation of implementing an effective stream channel BMP/restoration effort using the existing CONCEPTS model already developed for the Upper Truckee River on a short reach.