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 82 10.3.4 200 Year ARI Flood Figure A.4 shows the extent of flooding and the flood depths for the 200 Year ARI design flood. Flooding in the Alice Springs township is extensive, with the CBD almost completely inundated, and significant inundation of the Eastside and Gillen suburbs. Floodwaters overflow from the Charles River and drain south through the Braitling area towards the CBD. South of Heavitree Gap, floodwaters overflowing from the Todd River overtop the railway embankment and flow into Ilparpa Swamp. Overbank inundation on both the eastern and western floodplains of the Todd River is significant. 10.3.5 500 Year ARI Flood Figure A.5 shows the extent of flooding and the flood depths for the 500 Year ARI design flood. The extent and depth of flooding upstream of Heavitree Gap is significantly worse than for the 200 Year ARI flood, with areas immediately upstream of Heavitree Gap inundated by depths of up 5m. Downstream of Heavitree Gap the western floodplain is inundated almost completely between the railway and the Todd River. 10.3.6 Probable Maximum Flood (PMF) Figure A.6 shows the extent of flooding and the flood depths 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. South of Heavitree Gap very few areas are flood free, with the Amoonguna Settlement inundated by depths of up 1.5m due to floodwater overflowing from Emily Creek. 10.4 FLOOD HAZARD MAPPING Flood Hazard mapping was undertaken for the 100 Year ARI event, in order to identify areas of high flood hazard. The category for high flood hazard is as follows: Areas where flood depth is greater than 2m; or Velocity x flood depth is greater than 1; Figure 10.5 shows the 100 Year ARI extent of flooding and area of high flood hazard in accordance with the above criteria. 10.5 FLOOD FRINGE MAPPING Flood Hazard mapping was undertaken for the all modelled design events, in order to identify areas affected by shallow flooding on the edge of the flood event. Flood fringe areas are classified as areas where the depth of flooding is up to 0.15m (150 mm) above ground level. Figure 10.6 shows the 100 Year ARI extent of flooding and flood fringe areas.