Territory Stories

Alice Springs Flood Investigation and Floodplian Mapping Study

Details:

Title

Alice Springs Flood Investigation and Floodplian Mapping Study

Creator

WRM Water & Environment Pty Ltd; Northern Territory. Department of Lands, Planning & the Environment

Editor

Roads, Greg

Collection

E-Publications; PublicationNT; E-Books; EXTA1463

Date

2015-10-12

Location

Alice Springs

Description

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.

Table of contents

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

Language

English

Subject

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

Publisher name

WRM Water & Environment Pty Ltd

Place of publication

Darwin (N.T.)

Series

EXTA1463

Format

vii, 95 pages : colour maps ; 30 cm.

File type

application/pdf.

Copyright owner

Check within Publication or with content Publisher.

Parent handle

https://hdl.handle.net/10070/259732

Citation address

https://hdl.handle.net/10070/494349

Page content

0269-02-C1 12 October 2015 51 7 HYDRAULIC MODEL CALIBRATION 7.1 GENERAL The TUFLOW hydraulic model was calibrated against the March 1983, March / April 1988 and April 2000 flood events, and verified against the January 2010, February / March 2010 and April 2010 flood events. The calibration and verification events were selected to investigate model behaviour for flood events ranging from large floods with significant overbank flow (1983, 1988) to minor events where flow is confined within bank (2010 events). Such an approach will allow infiltration rates and bed scour within the Todd River to be predicted with some confidence. Predicted flood hydrographs generated by the calibrated URBS model (See Section 5) for the above events were adopted for use in the TUFLOW model calibration. The URBS model was also used to estimate local catchment runoff within the study area for use calibration of the TUFLOW model. Scour depths were applied to Charles and Todd River beds for each event in accordance with Table 6.5. Calibration of the TUFLOW model was based on recorded water levels at the Anzac Oval (G0060009), Heavitree Gap (G0060126) and Amoonguna (G0060040) stream gauges for the calibration and verification events. Surveyed flood debris marks along the banks of the Charles and Todd rivers were also available for use in model calibration for the March 1983 and March / April 1988 flood events. The extent of floodplain inundation during the 1988 flood event particularly on the western Todd River floodplain, south of Heavitree Gap was discussed with residents present at the time of flooding. GHD (1996) also provides details of eyewitness accounts of flooding behaviour in Alice Springs, particularly in the area between the Stott Terrace bridge and Heavitree Gap. 7.2 MARCH 1983 CALIBRATION 7.2.1 Recorded Stream Gauge Data Figure 7.1, Figure 7.2 and Figure 7.3 show the recorded and predicted water level hydrographs at the Anzac Oval, Heavitree Gap and Amoonguna stream gauges for the March 1983 flood event calibration. The following is of note with regards to the recorded and predicted hydrographs at the stream gauges: An excellent fit has been achieved between recorded and predicted water levels at the Anzac Oval stream gauge, particularly for the first flood peak. The second and third flood peaks are slightly under and over predicted respectively. This is consistent with results of the URBS model calibration at this location (refer Figure 5.5). The hydraulic model is unable to accurately reproduce the recorded water levels at Heavitree Gap. The model over-predicts water levels at the gauge for the first and third flood peaks by 0.5m and 0.8m respectively. Although the use of URBS model predicted discharges may be the cause of some error at this location (particularly for the second and third flood peaks), it is unlikely to cause errors of the magnitude evident in Figure


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