Alice Springs Flood Investigation and Floodplian Mapping Study
WRM Water & Environment Pty Ltd; Northern Territory. Department of Lands, Planning & the Environment
E-Publications; PublicationNT; E-Books; EXTA1463
Made available via the Publications (Legal Deposit) Act 2004 (NT).; WRM Water & Environment (WRM) was commissioned by the Department of Lands & Planning (DLP) to undertake a flood study of the Todd River in the Alice Springs area. The aim of the study is to develop a 2 dimensional flood model, which allows flood flow in a complex flood plain to be modelled, to determine the extent and severity of riverine flooding in the town of Alice Springs and the Alice Springs rural area south of Heavitree Gap. The purpose of the study is to produce floodplain maps of the Alice Springs and its rural area for land use planning and counter – disaster purposes. This study is an extension of the Alice Springs Farms Area Floodplain Mapping Study (WRM, 2006), undertaken by WRM on behalf of the Department of Planning & Infrastructure in 2006 in order to develop detailed Todd River floodplain maps for the rural area south of Alice Springs.
1. INTRODUCTION -- 2. CATCHMENT DESCRIPTION -- 3. AVAILABLE DATA -- 4. CALIBRATION AND AND VERIFICATION EVENTS -- 5. HYDROLOGIC MODEL CALIBRATION AND VERIFICATION -- 6. HYDRAULIC MODEL DEVELOPMENTLOPMENT -- 7. HYDRAULIC MODEL CALIBRATION -- 8. FLOOD FREQUENCY ANALYSIS -- 9. DESIGN EVENT HYDROLOY -- 10. DESIGN FLOOD LEVELS AND EXTENTS -- 11. CONCLUSION -- 12. REFERENCES
Flood control -- Northern Territory -- Alice Springs; Flood damage prevention -- Northern Territory -- Alice Springs; Floodplain management -- Northern Territory -- Alice Springs; Alice Springs Flood Investigation; Floodplain Mapping
WRM Water & Environment Pty Ltd
vii, 95 pages : colour maps ; 30 cm.
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0269-02-C1 12 October 2015 86 recorded water levels at the Heavitree Gap gauge for discharges greater than about 150 m3/s. Possible reasons for the problems with this gauge are discussed in Section 3.4.5. It is recommended that the Heavitree Gap gauge is relocated further downstream, potentially upstream of the Ross Highway Bridge. With the exception of the Heavitree Gap gauge, the TUFLOW model adequately represents historical flood behaviour for all calibration and verification events. The calibrated TUFLOW model was used to estimate design flood levels along the Todd River channel and flood depths and extent maps across the study area for the six design floods. In addition, areas of high flood hazard were identified for each design event. The following issues with respect to flooding in the Alice Springs township and rural area are of note: For the 20 Year ARI design flood overbank inundation in the town area north of Heavitree Gap is minor, occurring between Traeger Park and Stephens Road, and upstream of the Stott Terrace bridge. South of Heavitree Gap some overbank inundation occurs south of the Ross highway bridge, at the racecourse and the rural residential are on Colonel Rose Drive. For the 50 year ARI design flood, floodwaters overflow the eastern bank of the Todd River at the Wills Terrace causeway inundating parts of Undoolya Road and Lindsay Avenue to shallow depths. Todd River floodwaters also overflow west into the Alice Springs CBD before flowing south towards Gap Road. Significant breakout of floodwater occurs south of the Stott Terrace bridge inundating properties between Traeger Park and Heavitree Gap. South of Heavitree Gap floodwater overflows from the western bank of the Todd River immediately upstream of Ilyiperenye Hill, combining with water overflowing from Ilparpa Swamp and draining south along the St Marys Creek channel. There is substantial flooding of the AZRI site and the Todd River western overbank area due to Todd River overflows. For the 100 year ARI design flood, overflows from the Charles River occur north of the CBD, inundating residential properties in the Braitling area. Floodwater overflowing from the Todd River upstream of Wills Terrace inundates streets and low lying properties in the Eastside area. Significant volumes of floodwater overflow south of Wills Terrace inundating the majority of the CBD to depths of up to 0.5m. The urban areas south of Traeger Park are almost completely inundated to depths of up to 0.8m. The Stuart Highway and railway embankment upstream of Heavitree Gap are inundated and impassable. The Stuart Highway is inundated as far north as Traeger Park. South of Heavitree Gap, floodwaters overflow from the Todd River between the Palm Circuit causeway and Ross Highway bridge. On the western overbank, overflowing floodwater drains south along the railway embankment before overtopping the Stuart Highway at Ilyiperenye Hill and combining with water overflowing from Ilparpa Swamp. On the eastern overbank floodwater drains through the properties on Palm Circuit and Palm Place towards Ragonesi Road. Overbank flooding on the western floodplain is more severe, with much of the AZRI site and rural residential area inundated by depths between 0.3m and 0.6m. For the 200 Year and 500 Year ARI design floods, most of the CBD area is inundated to varying depths and the extent of flooding south of Heavitree Gap covers the majority of the western floodplain. For the PMF, almost all of the urban areas within the model extent are inundated by over 1m, and immediately upstream of Heavitree Gap flood depths are in the order of 12m.