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 72 Areal reduction factors (ARFs) for the Todd River for design events up to and including the 100 Year ARI storm were calculated using the Conservative Envelope Model based on Queensland Data, as outlined in the Final Report on Extreme Rainfall Estimation Project: CRCForge and (CRC) ARF Techniques, Queensland and Border Locations (Hargraves, 2004). Table 9.2 gives the adopted ARFs for the Todd River catchment. ARFs have been applied to the design rainfall intensities reported in Table 9.1. Table 9.2 Adopted Areal Reduction Factors, Todd River Catchment, Design Events Up to and Including 100 Years ARI Storm Duration (hours) Areal Reduction Factor <18 0.87 24 0.89 30 0.90 36 0.91 48 0.93 72 0.95 The Hargraves (2004) ARF calculation method was preferred to the ARFs given in Figure 1.7 in Book 2, Section 1.6 of ARR (1998) for inland Australia. The ARR (1998) values are calculated from data for American catchments in Arizona, while the Hargraves (2004) calculation method incorporates data from catchments close to the NT QLD border regions, which is considered more appropriate for use in this study. Further, adopting the ARR (1998) ARFs would result in substantial reduction of design rainfalls across the catchment, in turn requiring the use of unrealistic low rainfall losses in order to reconcile URBS model peak discharges with FFA peak discharge estimates. It should be noted that ARFs were not applied to design rainfalls in WRM (2006) due to the issues associated with adopting ARR (1998) values. 9.2.2 Probable Maximum Precipitation Event PMP rainfall patterns and intensities were estimated using the Generalised Short Duration Method (GSDM) (BOM, 2003a) and the Generalised Tropical Storm Method (GTSMR) (BOM, 2003b). The GSDM is suitable for small catchments (up to 1,000 km2) and for short durations (up to 3 hours), while the GTSMR is applicable to durations of 12 hours and greater. PMP rainfalls for durations between 3 and 12 hours were interpolated between the GSDM and GTSMR estimates. Table 9.3 shows the adopted PMP rainfall depths for the Todd River catchment for the various storm durations analysed. For the estimation of PMP discharges, the spatial distribution of PMP rainfall across the catchment was determined in accordance with the methodology outlined in BOM (2003a) for the short duration storms and BOM (2003b) for the long duration storms.


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