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Alice Springs recreational dam hydrology report project 6



Alice Springs recreational dam hydrology report project 6


Jackson, D.; Paige, D.


E-Publications; E-Books; PublicationNT; Report no. 12/1979







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Northern Territory Government

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Report no. 12/1979

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Attribution International 4.0 (CC BY 4.0)

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Northern Territory Government



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Technical Report WRD79012 Viewed at 00:02:46 on 18/02/2010 Page 146 of 153. I I I I I I I I I I I I I I I I I I I I 43 Although the percentages in table 5 are not completely correct in that the 5% trap efficiency is taken from Brune's curve which was derived empirically using annual yields; they are possibly more indicative of sediment-reservoir behaviour for intermittent rivers than the values in table 4. This is especially the case for higher return period flows which contribute a large proportion of the sediment load~ 3.4.2 Trap Efficiency Model - Camp's Method. Camp's method (Chan 1975) is frequently used in the design of sedimentation retention ponds. The method calculates trap efficiencies in terms of a relation between particle settling velocity and the forward velocity in the pond. As such, outflow characteristics are accounted for explicitly rather than implicitly as in the retention time concept used in Brune's method. According to Camp's method, the trap efficiency decreases as the basin outflow increases. Table 6 shows trap efficiencies for different particle sizes and peak flows. Trap efficiency E is defined as; E = w where W = settling velocity for a given particle size, (Table 7) and Q /A is the overflow velocity of the basin, which is dependent on the surface area A .. Table 6 TRAP EFFICIENCIES FOR DIFFERENT PARTICLE SIZES AND PEAK OUTFLOW RATES, (PERCENT) Return Period Peak Outflow Trao Efficiency ( %) (Years) Rate (m 3 /s) VFSa CS MS FS VFS 5 170 100 100 100 71 20 10 250 100 100 95 51 14 20 350 100 100 91 38 10 50 500 100 100 85 27 7 100 620 100 99 80 22 6 500 950 100 95 55 14 4 NOTE ~ Abbreviations are explained in Table 7.