Flood Warning and Damages in Alice Springs: Part 1 Executive Summary. Part 2 Tangible Damages Part 3 Intangible Damages & Emergency Procedures
Handmer, John; Smith, D. I.; Greenaway, Mark
E-Publications; E-Books; PublicationNT; Report ; 53/1989
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Power and Water Authority
Report ; 53/1989
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Technical Report WRA89053 Viewed at 03:02:00 on 18/02/2010 Page 120 of 139. I I I I I I I I I I I I I I I I I I I I 2. PROJECT DESCRIPTION The site for the dam is identical to that outlined in the EIS. The arrangement of the dam is similar to that outlined for the "full" dam in the EIS. The "partially full" dam differs in the following respects: the overtlow level has been reduced from EL658 to EL64S and has capacity to draw down further to EL640 on demand. it has an uncontrolled 104m diameter pipe running under the main dam instead of a controlled 0.75m diameter pipe. the top of bank level is reduced from EL671.5 to EL670.0. the control spillway and the main spillway have been incorporated into a single structure, thereby reducing the length of the spillway channel excavation. ._c /;-..<! 1;-'" d,,;<.., LI .~ an auxiliary spillway for the most extreme floods would be provided in lieu of three saddle dams at the eastern end of the dam. The "partially full" dam would have four normal levels of outlets or spillways. These would comprise the low level outlet, control spillway, main spillway, and auxiliary spillway in order of increasing elevation. The arrangement of the dam is shown in Figs 1 & 2. Low Level Outlet .' The low level outlef would be an uncontrolled pipe approximately 104m in diameter and passing below the main dam adjacent to the eastern abutment. This means it would not have any valves or gates which could be closed to hold the water level above EL64S.0. The low level outlet pipe would be constructed at a level of approximately EL 640.0 in order to maxin1ise it's value for flow diversion during construction, reduce the effect of inlet losses on tlow capacity and allow for the possibility of lowering the dam level if required. The upstream intake structure would include an open outlet at EL645 complete with trash grate to prevent entry of large debris and an alternative outlet at EL640 which would remain open during the initial stages of construction. Following completion of the main embankment to a secure height the outlet at EL640 would be valved off and the water level in the dam allowed to rise to the permanent outlet at EL64S. An energy dissipater in the fOfm of a hydraulic jump basin recessed below the river bed level would be constructed at the outlet. The maximum discharge from the low level outlet would be approximately 20m3/s. 2