Alice Springs recreational dam hydrology report project 6
Jackson, D.; Paige, D.
E-Publications; E-Books; PublicationNT; Report no. 12/1979
1979-10-01
Date:1979-10
English
Northern Territory Government
Darwin
Report no. 12/1979
application/pdf
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
https://creativecommons.org/licenses/by/4.0/
https://hdl.handle.net/10070/228346
https://hdl.handle.net/10070/674275
Technical Report WRD79012 Viewed at 00:02:46 on 18/02/2010 Page 70 of 153. I I I I I I I I I I I I I I I I I I I I 44 TABLE 7 ~ SETTLING VELOCITIES OF SEDIMENTS IN WATER AT 16'C (AMERICAN GEOPHYSICAL UNION CLASSIFICATIONS) SEDIMENT CLASS Very Coarse Sand Coarse Sand Ncdium Sand Fine Sand Very Fi.ne Sand Coarse Sil t }~edium Silt Fine Silt Very Fine Silt ABBREVIATION vsea CSa MSa FSa VFSa CS MS FS 'iFS 3.4.3 Discussion DIANETER (mm) 2.000-1.000 1. 000-0.500 0.500-0.250 0.250-0.125 0.125-0.062 0.062-0.03: 0.031-0.016 0.016-0.008 0.008-0.004 SETTLING Velocity (m/s) 0.27 - 0.15 0.15 - 0.07 0.07 - 0.03 0.03 - 0.01 10-2 - 3.0x10-' 3.01<10- 3 - 8.2xlO-'+ 8.2xlO-' - 2.0xlO- 4 2.0xlO- - 5.2x10- s 5.2xlO- 5 - 1.3xlO- S The estimates of capacity deple~ion in Table 4 and the estimates of time to fill the reservoir with sediment are conservative for two reasons. Firstly, Brune's method makes no allowance for flow through velocities which would be expected to be significent because of the short length of the reservoir~ Camp's method shows that trap efficiences decrease as flow through velocities increase. This result is hinted at in deriving the 5% trap efficiency estimates (Table 5) using Brune's method. Secondly, no differentiation is made between particle sizes in Brune's method. Camps method shows {Table 6 ) that only VFSa l CS t and MS fractions are likely to be trapped at a trap efficiency in tIle order of 95%. Better estimates of useful reservoir capacities and reservoir life will require the measurement of suspended sediment particle size fractions. These measurements are not available at present.