Sediment transport along lower Fraser River - 1. Measurements and hydraulic computations

A comprehensive program of sediment transport measurements was conducted al ong lower Fraser River, British Columbia, between 1966 and 1986. The data y ield a detailed sediment budget. Annual total suspended loads at three stat ions are virtually identical, averaging 17 x 10(6) tonnes/year (t yr(-1)). The suspended sand load is about 5.5 x 10(6) t yr(-1), about one third of t he total. In the gravel bed reach of the river the sand behaves as wash loa d. Significant transport of gravel begins at Agassiz at a discharge of abou t 5000 m(3) s(-1). The annual gravel transport was estimated to be about 0. 23 x 10(6) t yr(-1), only 1% of the total load. All of this material is dep osited in the reach upstream of Mission. At Mission, sands finer than 0.177 mm make up more than 50% of the suspended sand load but are virtually abse nt from the sand bed. Therefore a portion of the sand load at Mission is wa sh load. The total bed material load here was estimated to be 3.0 x 10(6) t yr(-1), about 18% of the total sediment load. Virtually all of the bed mat erial load was transported in intermittent suspension near the bed, less th an 5% occurring as bed load. In the long term the suspended sand load upstr eam is approximately equal to the total sand load at Mission. However, with in individual years some of the sand is stored within the reach temporarily and then reentrained later.