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 33 Table 5.4 Adopted URBS Model River Reach Length Factors Region River Reach Length Factor 1 0.3 2 1.5 3 1.0 4 0.6 In general terms, the fit between recorded and predicted discharge hydrographs is good. The adopted model calibration represents a compromise in the fit between the three events. It was possible to obtain a better fit for all stations if the URBS model parameters were varied from event to event. However, considering the uneven distribution of rainfall stations within the catchment and uncertainties in rating curves for the stream gauging stations at Anzac Oval and Heavitree Gap further refinement of model parameters were not considered necessary. 5.4.2 March 1983 Flood Event Figure 5.3 to Figure 5.7 show the recorded and predicted discharge hydrographs in the Todd River at Wigley Gorge (G0060046), Anzac Oval (G0060009) and Heavitree Gap (G0060126), Charles River at Big Dipper (G0060047) and Emily Creek Upstream Undoolya Road (G0060017) for the March 1983 flood event. The following comments are made with respect to the calibration results. The results show that an excellent fit has been obtained for the first peak at Wigley Gorge, Anzac Oval and Upstream Undoolya Road. The first flood peak appears to have been overestimated at Heavitree Gap; however the shape of this hydrograph is not consistent with the upstream Anzac Oval stream gauge. The initial peak in the Charles River at Big Dipper is not reflected in recorded rainfall. The second peak is reproduced well at Wigley Gorge, but is under-estimated at all other gauge locations with the exception of Emily Creek at Undoolya Road, at which the model slightly over-predicts the peak. The third peak has been reproduced well at Wigley Gorge and in the Charles River at Big Dipper, but the peak at Anzac Oval has been over-estimated by the model. It is possible that this is due to the model overestimating local catchment flows draining to the Todd River in between Wigley Gorge and Anzac Oval, based on the high localised rainfalls recorded at rainfall station G0060009. It should be noted that the rating curve at Heavitree Gap is known to be unreliable at high flows. The third peak in Emily Creek has been underestimated by the model. The low flows have been overestimated at all stations. It is expected that the differences in low flows are attributed to the high infiltration rates from the bed of the Todd River into the underlying aquifer. High infiltration rates are unlikely to impact on the flood peaks but can significantly impact on the lower flows. Infiltration has not been included into the URBS model. The overall shape of the predicted hydrograph for all three peaks is good, especially for the Wigley Gorge station. It is noted that the quality of the rating curves for the Anzac Oval and Heavitree Gap stations are not considered as good as for the Wigley Gorge station. The peak discharges at Wigley Gorge and Anzac Oval are similar despite the fact that the catchment area increases by some 100km2 (28%) between the two stations. An analysis of the URBS model shows that the Charles River catchment, which drains in downstream of Wigley Gorge rises and falls before the Todd River peak arrives.


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