Factors controlling variations in suspended sediment concentration for single-valued sediment rating curves, Fraser River, British Columbia, Canada
✍ Scribed by Henry M. Sichingabula
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 376 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0885-6087
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✦ Synopsis
Functional (regression) and cause-and-eect analytical methods were employed in the investigation of factors controlling single-value sediment±discharge relationships for individual hydrological events in the Fraser River Basin. Of 1025 hydrological events identi®ed in the 97 years of the 9-stations discharge record monitored by the Water Survey of Canada (1960±1988), 49 were associated with linear, non-linear (concave and convex) sediment rating curves. Analysis revealed that time of events oered a partial explanation for the occurrence of single-valued curves because events occurring in isolation or in quick succession did not always produce singlevalued curves owing to variations in hydrograph characteristics and temporal and spatial peak attenuation factors. Hydrologically, linear and non-linear sediment rating curves were distinguished by the in¯uence of preceding discharge or antecedent moisture, which tends to generate quick or delayed runo, thereby causing rapid or slow increases in sediment concentration in concert with discharge changes. Hydraulically, linear curves were shown to be controlled by rates of stream bed scour (rising stage) similar to those for channel ®lling (falling stage); concave curves by rates of scouring (rising stage) similar to those of ®lling but dierent from those of rescouring (falling stage); and convex curves by rates of ®lling and scouring (rising stage) dierent from those of ®lling and rescouring (falling stages), all in relation to the timing of the exceedance of the threshold discharge for stream bed scour. Meteorologically, bed scour and ®ll approximately coincided with the timing of precipitation, if any, on the rising and/or falling stages under subzero (T 4 0 8C), low (1 4 T 4 9 8C) and moderate (10 4 T 4 19 8C) temperature conditions. It is concluded that a combination of temporal, spatial, hydrological, hydraulic and meteorological factors control variations in sediment concentration during single hydrological events on the Fraser River in a complex fashion. Multivariate analysis of these factors should greatly improve prediction of sediment transport in the Fraser River Basin.