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
Check within Publication or with content Publisher.
Technical Report WRA89053 Viewed at 03:02:00 on 18/02/2010 Page 103 of 139. I I I I I I I I I I I I I I I I i i I i EXPLANATORY NOTES FOR TABLE 1 NOTE 1 N()'rl" " . ~ ... ..., NOTE 3 NOTE 4 NOTES NOTE 6 This represents the eXIsting cODdition wah no nood mitigation dam at any point along the river. The "full" dam was the option proposed in the EIS or October i990, and from a technical viewpoint is still the most favourable option. It comprises a dam with a standing water level of EL 658. Flood nows up to the 100 year flood are throttled through a control spiilway with an inven at EL 658. Larger Hoods discharge Vla a main spillway at EL 665m and an auxiliary spiilway at EL 667m. The top of embankment level of the dam is EL 670m, corresponding to the probable maximum Hood. The 'partially full" ,tun is simIlar to the "full" dam except that it has an open uncontrolled pipe passing beneath the dam. After the passing of the flood the water level behind the dam drains down to the level of the pipe. The rate at which water drains out depends on the pipe size. The control spillway, main spillway, and auxiiiary spillway are unaltered because it is not unusual to have two !loods foilowing one after the other, and the dam may not have sufficient time to drain before the next tiood. Also the storage volume below the control spillway level is not large compared to the overall storage capacity or the dam and the outlet pipe capacity is small compared to the potential river 110ws. The "empty" darn has a large runnel 6.5m in diameter at the bed level of the river through which noods up to the 100 year Hood are discharged at velocities of more th:ll1 15 m} sec.' For larger Hoods, How passes over the main spillway at EL 664m and the auxlliary spillway at EL 666.25. The top of bank level for the dam ';;ould be EL 669.0. Estimates are given in terms of April 1991 dollars,. They vary slightly from those given in the EIS due to escalation since the earlier estimates were prepared, and rationalisations in design. Estimates are preliminary o~y. . The estimate for the "empty" dam may underestimate the tinal cos!. There are some technical difficulties with such a large diameter tunnel which have not been fully resolved. Thus there is greater potential for escalation of this figure than for other opnons.