Bed-material transport rate derived from delta progradation in a small alpine basin, Fitzsimmons Creek, coast mountains, British Columbia

A sediment budget was determined for Fitzsimmons Creek in order to assess the long-term bed-material efflux from a high-energy, debris-flow dominated alpine stream in the Coast Mountains of British Columbia. The primary component of the thesis (Part1) examines the long-term bed-material transport rate from morphologic data, sonar bathymetry, and ground-penetrating radar surveys of the fan-delta built by Fitzsimmons Creek and recorded on sequential aerial photography for the period 1947-1999. The average annual bed-material transport rate is 1.60 ± 0.28 104 Mg yr-1 for the 52-year period, with a range of 2.20 x 104 Mg yr1 for decadal estimates. Considerable temporal variability of the average bed-material efflux is evident over the 52-year record. The length of time required to measure a stable average annual bed-material transport rate in this particular system appears to be not less than 50 years. A secondary component of the thesis (Part 2) examines the total sediment budget based on direct measurements of bed-material accumulated in the fan-delta and estimates of suspended-sediment over the 52-year period. The long-term minimum specific sediment yield is 0.57 ± 0.14 Mg km-2 day-1 based on direct measurements and the estimate of the specific sediment yield for this system is 0. 90 ± 0 .48 Mg km- 2 day-1. A significant proportion of the total sediment load (averaging 49% over the 52-years) is deposited as bed-material in Fitzsimmons Creek's fan-delta.