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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 69 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 empiricaJ.ly 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 iligher return period flows which contribute a large proportion of tIle sedimerlt load. 3.4.2 Trap Efficiency Model - Camp's Method. Camp's method (Chan 1975) is frequently used in the cieslgrl of sedimentation retention ponds. The method calcl]]ates trap efficiencies in terms of a relation botween particle set~ling velocity and the forward velocity ill tile pond. As such, outflow characteristics are accotlnted for explicitly rather than implicitly as in the retention time concept used in BruIle'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 p<!ak flows. Trap efficiency E is defined as; E = w where W = settling velocity for a given particle sizer (Table 7) and Q /A is the overflow velocity of the basinl which fs dependent on the surface area A. Table 6 'TRAP EFFICIENCIES FOR DIFFERENT PARTICLE SIZES AND PEl'.K OU1'FLO~l RATES, ( PERCENT) Pcturn Period Pc ak Outflow Trap Effjciency ( %) (Years) Rate (ms/s) VFSa CS HS FS VFS t> 170 100 100 100 71 20 10 250 100 100 95 ~J 14 20 350 100 100 91 38 10 50 500 100 100 85 27 7 100 620 100 99 80 22 6 sao 950 100 95 55 14 4 NOTE 1 Abbreviations are explained in Table 7.