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
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Power and Water Authority
Report ; 53/1989
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Technical Report WRA89053 Viewed at 03:02:00 on 18/02/2010 Page 109 of 139. , , , ~ , I I I I I I I I I I I I I I I f NOTE 3! NOTE 32 NOTE 33 NOTE 34 NOTE 35 NOTE 36 NOTE 37 1>10st sedimentation occurs within the permanentlv inundated areas, which . . is ignored for the purpose of !lood mitigation. Onl v deposition above EL 658 would affect nood mitigation perrormance, Sedimentation wouid reduce the Hood storage volume. and would have some aftect on Ilood mitigation. However because the dam has been designed to mitigate t100ds even if the dam has not had time to empty, the design Hood mitigation perrormance is retained until sedimentation extends above EL 658. As the dam was assumed empty tor design purposes, sedimentation will reduce t100d mitigation performance. In time the spillway capacity of the dam will be inadequate and either the embankment will require raising or the spiilway enlarging. Large and rapid changes in water level cause rapid changes in loading on the dam and can cause problems with piping of cracks and slope stability. The larger and more rapid the change, the worse it is for dam and slope stability. Drying out of the impermeable clay core may occur if the dam remains empty for long periods of time. Drying out may lead to cracking of the core which is undesirable for reasons of daln safety. The time of inundation at Tnyere Akerte is dependant on the size oi the low level outlet. The times shown represent the average number of days per year that the dam water level would exceed EL646 for a outlet level of EL645 based on the fur 18 years of stream 110w and rainthll records. Due to evaporation imd in'filtratia'n losses the dam water level would also drop below 644 for up to 42 days per year and fall as low as 642.9 during the the same period. Tnyere Akerte comprises an area rather than an individual tree or rock so reference should be made to contour drawings ior ruther detail on inundation. This column refers only to potential for future multiple use. Refer Section 4.08 of EIS.