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 28 Channel routing is based on the non-linear Muskingum Model. The channel routing storage discharge relationship is given by: n du c chnl ))1(( * QxQx S Ln fS where Schnl is the channel storage (m 3 h/s); is the channel lag parameter f is the reach length factor; L is the length of reach (km); Sc is the channel slope (m/m); QU is the inflow at upstream end of reach (includes catchment inflow) (m3/s); Qd is the outflow at downstream end of the channel reach (m 3/s); x is the Muskingum translation parameter; n is the Muskingum non-linearity parameter (exponent); and n* is the Manning's 'n' or channel roughness. In the above equation, and f are the principal calibration parameters. Note also that is a global parameter, whereas f can be varied for each channel reach. URBS allows the user to select one of several standard loss models. The available options are: initial and continuing loss model, proportional loss model, Manley-Phillips infiltration model and water balance model. The initial and continuing loss model was adopted for the Todd River catchment. This model assumes that there is an initial loss of il mm before any rainfall becomes runoff. After this, a continuing loss rate of cl mm per hour is applied to the rainfall, subject to the limit of the soil infiltration capacity (IFmax). The loss rates can be specified globally to the entire catchment or individually to each sub-catchment. Full details of the URBS model and its features are given in the URBS User Manual (Carroll, 2007). 5.2 URBS MODEL CONFIGURATION The URBS model developed for this study was based on model developed as part of the WRM (2006) study. The WRM (2006) URBS model was updated and modified to provide additional details of local catchment flows within Alice Springs, and also improve the estimation of local catchment runoff south of Heavitree Gap in areas such as the Blatherskite Valley and the Kilgariff development area. The model was also extended to include the Emily Creek catchment area. Figure 5.1 shows the configuration of the Todd River URBS model adopted for use in this study. The model covers the entire Todd River catchment upstream of Amoonguna, and also includes the Emily Creek catchment. It consists of 71 sub-catchments, with 37 of these upstream of Heavitree Gap. Table 5.1 shows the areas for each sub-catchment used in the model. A detention basin was added to the model at Heavitree Gap to better model the choking effect of the Gap restriction at very high discharges. A description of how the detention basin characteristics were derived is given in WRM (2006). Each sub-catchment of the model was assigned the rainfall from the nearest pluviograph station. A constant loss model (initial loss /continuing loss) was adopted uniformly for all sub catchments.