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 132 of 139. I I I I I I I I I I I I I I I I I I I I - -..... /~lt~. ~I..:: H LJ) ------. Reference is made to the need for clearing the submerged area of vegetation. As this is not proposed some maintenance to remove t10tsam may be required. Appenrlh: E Todd River Catchment This report is not affected by the revised proposal. Appendix F Flood Warning and Damages This report is not affected by the revised proposal. Appendix G Todd River Bed Degradation Study The study remains largely applicable to the "partially full" dam proposal. One difference is that the smaller more frequent floods would undergo significant additional attenuation through the "partially full" darn. Until the water level in the darn reaches the control spillway, all discharge is limited to 20mJ/s, the capacity of the low level outlet. The Hood is much less, but it is spread out over a longer time so that the total volume of discharge from the dam is approximately the same as if the dam had not been built. The sediment carrying capacity of the river increased exponentially with t1ow. The attenuation of flow therefore means that although the total volume of flow down the river would remain the same, the rate of sediment degradation would be less. It is estimated that the average rate at which replenishment sand and gravel should be carted from the sediment traps to the spillway channel would be 8500m3!annum rather than 12000m'/annum for the "full" dam. Appendix H Flood Mitigation Proposal for Alice Springs by S. Smith This report is not affected by the revised proposal. Appendix I Levee Bank Option This report is not affected by the revised proposal. Appendix J Water Quality Issues and Groundwater and Surface Water System Impacts Salinity levels in the water pool upstream of the dam are likely to be higher than those predicted for the "full" dam, due to a high surface area to volume ratio for the water body. They would still be less than those experienced in most natural waterholes along the river. Any significant tlows in the river would quickly dilute salinity levels and flush the water pool. Thus a long term build up of salinity would not be expected. Some management may be required to remove tlotsam. 14