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 31 5.3 CALIBRATION AND VERIFICATION METHODOLOGY The URBS model was calibrated to achieve the best possible fit between recorded and predicted discharge hydrographs at the various gauging stations within the catchment for the March 1983, March/April 1988 and April 2000 flood events. The calibrated model was then verified by comparing the model predictions against the discharge hydrographs recorded at various gauging stations for 11 verification events listed in Table 4.1. 5.4 CALIBRATION RESULTS 5.4.1 General The URBS model was calibrated against recorded discharge hydrographs at Wigley Gorge, Big Dipper, Anzac Oval, Heavitree Gap and Upstream Undoolya Road gauging stations. However, for reasons given in Section 3.4, the emphasis of the calibration was achieving the best possible fit between the predicted and recorded discharge hydrographs at the Wigley Gorge station. For all stations, the calibration attempted to match the predicted and recorded flood peaks and volumes, and also the shape of the hydrographs, with a single set of model parameters for the entire catchment. The following is of note: The adopted global URBS parameters for the two calibration events are shown in Table 5.2. These parameters are generally consistent with the typical range of parameters given in the URBS user manual (Carroll, 2007). However, the non-linearity factor is somewhat lower than the typical values because of the peaky nature of floods in the Todd River. The adopted initial and continuing losses for the three events are shown in Table 5.3. To better reflect the variation in hydrologic characteristics and topography of the various river and tributary reaches, the catchment was divided into 4 regions and a consistent set of reach length factors were adopted for each of the 4 regions. The adopted regions are shown in Figure 5.2. The adopted reach length factors are shown in Table 5.4. Table 5.2 Adopted URBS Model Global Parameters Parameters Value Channel Lag Parameter 0.2 Catchment Lag Parameter 5.0 Catchment Non-Linearity Factor m 0.55 Soil Infiltration Capacity (mm) IFmax 500 Table 5.3 Adopted Calibration Event Initial and Continuing Loss Rates Event Initial Loss (mm) Continuing Loss (mm/hr) March 1983 120.0 6.00 March/April 1988 50.0 6.00 April 2000 115.0 2.75
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