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Inquiry into the Alice Springs Recreation Lake : submission by Department of Transport and Works



Inquiry into the Alice Springs Recreation Lake : submission by Department of Transport and Works


Marquardt, A.


E-Publications; E-Books; PublicationNT; Report ; 1/1983




Made available via the Publications (Legal Deposit) Act 2004 (NT).


Date:1983-12; Contains: Floodplains Management Alice Springs Impacts of Todd River Flooding. Also filed in Alice miscellansous collection A0342, A0343.



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Dept. of Transport and Works

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Report ; 1/1983

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Technical Report WRD83001 Viewed at 14:07:22 on 29/07/2010 Page 10 of 64. a r g , :., . , " - ~~ ~ ~:';;~~<';'-. " " Given that the Todd River floods out 20 kilometres downstream from the Sl~e, and that it could reasonably be expected that the 4 million cubic metres of sediment trapped in the lake would otherwise have bee~ deposited at, or upstream of, the floodout, it may easily be concluded that- the eIIect of not having the dam would be an exacerbation of flooding in the region due to aggradation of the river bed and flood plain. Furthermore, such aggradation rr.ay have an adverse effect on recharge to the groundwater of the aquifers beneath the Brewer Plain (including the Mereenie sandstone) . In view of the latter argument, the point is made that the f d t f ~', ~,. 1- ~ b need or an cos - 0 ca ~cnmen'C managemen I... worKS snou d. r..a l.. e regarded simply as a prerequisite for (and hence cost to) to the proposed lake: catchment management works should be proceeded with irrespective of whether a dam is constructed. (g) Flood Mitigation The feasibility report (Transport and Works, 1979) found that the lake would significantly attenuate flooding; for instance, the 100 year flood would be reduced to a 20 year flood. (The 20 year flood is about the largest which the 'rive~ can accowmodate without extensive flooding to adjace~t land.) The impact of larger flooes would be reduced. , 1983, estimat.es the lfpresent 1;.oJorth ll of the afforded by the preferred spillway option to be million {or $8 million more than the cost of the mi tigation benefit was not fully recognised Drior because until that time the seriousness of the flood .was neither understood nor quantified; it was known that strous floods had occurred early in the century, but no ition of these had occurred in some 50 years, and ~~~~i~~~~Hi'~~t~~;i~:o~ns of .data and available c.nalysis techniql.:es ._: com9rehensive assessment. studies which were commenced in around 1978 led to on the subject in 1980 {Department of Transport and 1980). This report found that much of Alice Springs ",".V!,-'UJ,t=nt (including the central business district) has ccurred on flood prone land. For instance over 200 hectares '~~1i;~~:"ic'the tow!'. area woulc be inundated bv the 100 year flood; s would cost in the order of S50 miilion and require some residents to seek temporary "accoTI1..lllodation. Rarer floods be even more damaging. :'. '.