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 20 of 139. 4 'lver one ~~:-~ or- -~e hUl't "0 arga 'nc"c':ng th.,p ~ '_1. __ '-" ~.. "-' ,.l... <...:. _'- _. _' .... .:....:.. .L:_ :",n::-al busir.ess distcict (CBD) would be inundated by ar: ",x:reme flood exceeding che magni~ude of the 1:100 event. A : :20 Todd River even~ would flood or:ly a ~ew p:-opecties co :)ver floor level. However lit is irr.portant to n.o~e that. 5ignifican~ additional aceas are also flooded by urban jrainage surcharge. "lood water ir: the rivec chanr:el is ~ast flowing but the ~ater is fairly shall~~ i~ the ~rban area. The flooding is genecally of sho:-~ "'~ration, 12 to 18 ~Ours with peaks being reached within about 4 hours of flow :cmmence~ent in Alice Springs. Multiple peak ~loods are :ommon. Opportunities for flood warnings are ~herefoce ~uite limited. The Background to Damage Estimation flood damages are classified into tangible and intangible ~osses, with the tangible category fu=~her sub-divided into ~irect and indi~ect losses. An outline of the da~ages in 2ach class is given i~ Table 2.1. It is normal practice to estimate indirec~ losses as a p~opo~tion of di~ect damage. The calculation of direct losses is a func~ion 0: the type of proper~y, its susceptibility to flood loss and the depth ~,f flooding. Thus to obt.ain losses for a cOffimcnity the jirect damages for individual properties a:re summed. Property can be sub-divided in various ways. The initial division is into residential and commercial sectors, the catter is fUcther sub-divided accocding to size and vulnerability to flood damage. FOe each of the property :lasses a separate stage-damage curve is used. Stage-damage ,:urves are an averaging procedure tjat provides damage estimates for var~ous depths of overfloor flooding. The stage-damage curves employed in this study include estimates for loss of contents and for damage to the building. These correspond to the I'contents" and "building' definitions as used for household insurance. This approach has been standard practice i~ flood damage estimation for many years. It forms the basis fOe ANUFLOOD which is a commercially available computer package designed to assess direct urban flood damage. The inputs to the program are detailed information on each property in the flood-liable area, information on ~lood slope and the appropriate stage-damage curves. The Power and Watec Authority had already undertaken a flood study of Alice Springs, based on the ANUFLOOD program and procedures, prior to the flood of Eastec 1988. This included a detailed computer data base for each individual residential and commercial property, in the area thought, at the time of the origi~al survey, to be liable to inundation for floods cp to the 1% (1 in IOOyr) level. The residential stage-damage curves, on which this pre-flood study was ~ased, used field information collected by Northern 'Territory agencies. For the commercial sector the stagedamage curves supplied with ANU"LOOD were used. The residential stace-damage curves for Alice Springs ir.dicated a very much larger potential for flood damage than has been I I I I I I I I I I I I I I I I I I I I