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Submitted to: International Hydro-Science & Engineering International Proceedings
Publication Type: Proceedings Publication Acceptance Date: 1/29/2007 Publication Date: 3/1/2007 Citation: Kuhnle, R.A. 2007. Prediction of Bed Load Transport on Small Gravel-Bed Streams. In: Proceedings 7th International Conference on Hydroscience & Engineering, (ISBN: 0977447405), 10 pp. Interpretive Summary: Accurate determinations of the rate of sediment being moved on the bottom of stream and river channels are necessary because the sediment may fill reservoirs and reduce their capacity, may fill channels and cause flooding, may degrade water quality, and may cause instability of the channel banks which can cause the destruction of valuable agricultural and other lands. Rates of sediment movement in a stream are also an excellent indicator of the stability of the channels and land surfaces upstream of the measurement location. Accurate prediction of the rates of sand and gravel movement in streams and rivers for a given strength of flow and diameter of sediment are currently difficult to make. In this study measurements of the rate of sand and gravel movement made at three locations on the Goodwin Creek Experimental Watershed were used to compare to predictions from three transport relations that have been published in scientific papers. The results of these comparisons yielded that two of the relations predicted far in excess of the measurements while the other provided results that were within 50 percent of the measured movement rates of sand and gravel. Predictions between measured and predicted size of sediment in motion were within about 100 percent. Clearly more work is needed to develop relations that yield more accurate results. More studies of this type are needed to determine strengths and weaknesses of existing prediction techniques for a variety of streams and rivers. This type of information will provide guidance for future development efforts of improved predictors. Only with reliable methods of predicting sediment motion will real advances in environmentally sound management in agricultural and other watersheds be made. Technical Abstract: Rates and size distributions of bed load were calculated using 3 transport relations and compared to data collected on three streams with sand-gravel beds in the Goodwin Creek Experimental Watershed in north central Mississippi, USA. Bed load transport rates were greatly over predicted by two of the three relations with the third yielding values reasonably close to the measured values. Predictions of the median size of the bed load as compared to measured values were within about 100 percent for all three relations. The effect of bed material size distributions on the predicted rates from the 3 relations was evaluated and it was found that bed material sizes substantially larger than those measured in the field were needed to yield predicted rates close to those measured in the field for two of the three relations. The third relation yielded transport rates within about 50 percent of the measured rates using the measured bed material surface size distribution as input. |
