Climate Futures for Tasmania Flood Inundation Mapping

25 February 2011

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Executive summary

Changes to design flood hydrographs were assessed using projected changes to the magnitude of extreme rainfall events as a result of climate change. The Climate Futures for Tasmania (CFT) project has produced dynamically downscaled high-resolution climate change projections for Tasmania using the CSIRO Conformal Cubic Atmospheric Model (CCAM). The IPCC emissions scenario (high (A2)) was used alongside six Global Climate Models to simulate the Tasmanian climate to 2100. The A2 scenario better represents observed emissions since 2000 (Allison et al, 2009) and is used for the analyses presented in this report. The impact of climate change on flood levels was assessed for selected Tasmanian catchments, namely the lower reaches of the Mersey River, Forth River, Huon River and Derwent River. A series of design flood hydrographs for the 1 in 10, 1 in 50, 1 in 100 and 1 in 200 annual exceedance probability (AEP) events have been produced for the observed 1961-1990 period, then scaled for three future periods (2010-2039, 2040-2069 and 2070-2099) using the CFT projections. MIKE 11 and where available MIKE 21 hydraulic models were run for each of the selected catchments and each of the design floods. Results from MIKE 11 and MIKE 21 were used to generate flood inundation maps for use by the Tasmanian State Emergency Services (SES).

Hydrographs were developed for the four catchments of interest using a systematic stepwise process. Catchment areas and sub areas for each of the catchments were obtained from previous studies. Rainfall/runoff routing models, the rainfall/runoff routing network, non linearity exponent and the loss parameters for each of the models were sourced from previous studies. Design rainfalls have been obtained from either FORGE (Focussed Rainfall Growth Estimate Technique) or Australian Rainfall and Runoff. Climate Futures for Tasmania gridded rainfall data has been used to derive catchment wide information pertaining to the percentage change in design rainfall depth for the 1 in 10, 1 in 50, 1 in 100 and 1 in 200 AEP storm event across a series of durations.

Through a critical duration analysis for each of the catchments it was found that catchments which have a critical duration of greater than or equal to 72 hours are unlikely to see any significant increase in flood extent as the design rainfall is not projected to increase as a result of climate change. Conversely, catchments with a critical duration less than 72 hours will see proportional increases in rainfall and as such the critical duration will be more likely to shorten. It was found that short duration events are projected to become more intense as a result of climate change, and as such it is likely that those catchments with fast response times are likely to be the most impacted by climate change.

The peak discharge in the Mersey, Forth and Huon Rivers was found to increase significantly through to the end of the 21st century. The peak discharge in the Derwent River was not predicted to increase significantly due to the long duration of the critical storm events and significant upstream storages.

Pre-existing hydraulic models (Mike 11 and Mike Flood where available) were run with the updated hydrographs for the baseline period. Further adjustments were made to the hydraulic models to replicate future conditions more fully. In this analysis, sea level rise for each of the future periods was assumed to be 0.8m as is described in full in the IPCC (2007) and has been used by both the Victorian Coastal Council (2008) and the Queensland Department of Environment and Resource Management (2009) for planning purposes in the absence of national benchmarks. Water levels were found to increase across all catchments for all off the design floods investigated, with the exception of the Derwent, which showed only a minimal change in water level, well within the error bounds of the modelling.

i Error! Main Document Only. - Flood Inundation Mapping 25 February 2011

Flood inundation maps were developed from the analysis, showing the difference in flood extents between the baseline period and the start, middle and end of the 21st century.

ii Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Contents

Common Abbreviations 1

Glossary 2

1. Introduction 3

2. Limitations of this Study 5

3. Overview of Method 7

4. Hydrological Modelling 9

4.1 Modelling Approach 9

4.2 Previous Projects 9

4.3 Design Rainfalls 10

4.3.1 Design Rainfalls generated by CFT 10

4.3.2 Calculating Percentage Change in Rainfall from CFT Design Rainfall Inputs 10

4.3.3 Australian Rainfall and Runoff and CRC-FORGE Rainfalls 15

4.3.4 Adopted Design Rainfalls 15

4.3.5 Design Temporal Patterns 17

4.3.6 Spatial Patterns 17

4.4 Catchment Modelling 17

4.4.1 The Catchment Model 17

4.4.2 Dam and Storage Characteristics 18

4.4.3 Variation in losses with AEP for the design analysis 18

4.4.4 Validation of Catchment Model 19

4.4.5 The Design Model 19

4.5 Results for Design Flood Events 20

4.5.1 Critical Duration of the Outflow Flood 20

4.6 Comparison against Previous Studies 23

4.7 Flood Frequency Analysis 23

4.8 Hydrographs 24

5. Hydraulic Modelling 29

5.1 Previous Studies 29

5.2 Storm Surge 29

5.3 Sea level 29

5.3.1 Baseline 29

5.4 Sea Level Rise 30

5.5 Tributary Effects 30

5.6 Hydraulic Model 31

5.6.1 Mersey River Model 31

5.6.2 Forth River Model 32

5.6.3 Huon River Model 32

iii Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

5.6.4 Derwent River Model 33

5.7 Flood Modelling Results 34

6. Flood Mapping 41

7. Conclusion 43

8. Acknowledgements 45

9. Disclaimer 47

10. References 49

Appendices

A Climate Futures for Tasmania Rainfall Surface Map

B Flood Frequency Curves

C Hydrographs

D Flood Maps

E Mike11 Hydraulic Model Results

Annexure

List of figures

Figure 3-1 Summary of method used ...... 8

Figure 4-1 Annual rainfall over Tasmania simulated by a) A global climate model, b) Interpolated observations (AWAP, Jones et al. 2009), and c) 0.1 degree CCAM dynamically downscaled GCM (from Corney et al. 2010) .. 11

Figure 4-2 Mean rainfall depth for the 24 hour duration storm event between the baseline period and the end of the 21st century...... 13

Figure 4-3 Percentage change in rainfall depth between the baseline period (1961-1990) and the end of the 21st century (2070-2099)...... 14

Figure 4-4 Percentage change in Outflow Flood between 2070-2099 and the baseline period for the Mersey . 21

Figure 4-5 Percentage change in Outflow Flood between 2070-2099 and the baseline period for the Forth..... 22

Figure 4-6 Percentage change in runoff versus percentage change in design rainfall for the Mersey and the Forth catchments...... 27

Figure 5-1 Modelled Scenarios ...... 31

Figure 5-2 Modelled Scenarios ...... 32

iv Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Figure 5-3 Modelled Scenarios ...... 33

Figure 5-4 Modelled Scenarios ...... 34

Figure 5-5 Change in water level between the baseline period and the three future periods for the Mersey River downstream of Parangana Dam ...... 36

Figure 5-6 Change in water level between the baseline period and the three future periods for the Forth River downstream of Paloona Dam ...... 37

Figure 5-7 Change in water level between the baseline period and the three future periods for the Huon River downstream of Judbury ...... 38

Figure 5-8 Change in water levels between the baseline period and the three future periods for the Derwent River downstream of Meadowbank Dam ...... 39

List of tables

Table 4-1 Magnitude of the 24-hr duration 1 in 200 year AEP for 1961-1990 estimated from AWAP observations (5th/95th confidence intervals in brackets), with projected multi-GCM ensemble change for 2010-2039, 2040- 2069, 2070-2099, at five representative locations across Tasmania. AEPs estimated using a Generalised Pareto distribution. Multi-GCM ensemble AEPs estimated using the six downscaled GCMs for SRES A2. AEPs are expressed in mm, and deltas are expressed in mm and as a percentage change [in brackets], relative to the AWAP 1961-1990 baseline...... 12

Table 4-2 Adopted Design Rainfall for the Forth River Catchment below Paloona (mm) ...... 16

Table 4-3 Adopted Design Rainfall for the Mersey River Catchment below Parangana (mm)...... 16

Table 4-4 Adopted Design Rainfall for Huon River Catchment below Judbury (mm)...... 17

Table 4-5 Adopted Design Rainfall for the Derwent River Catchment below Meadowbank (mm)...... 17

Table 4-6 Storage Characteristic Data ...... 18

Table 4-7 Variation of Initial and Continuing Loss with AEP...... 19

Table 4-8 Baseflow into the Derwent River Catchment ...... 19

Table 4-9 Critical Outflow and Inflow Durations ...... 20

Table 4-10 Comparison with the previous results for the 1 in 100 AEP design flood...... 23

Table 4-11 Details of Flood Frequency Analysis ...... 24

Table 4-12 Scaling Factors used in deriving flood hydrographs...... 24

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Table 5-1 Base Case Sea Level ...... 29

Table 5-2 Adopted Sea Level ...... 30

vi Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Common Abbreviations

AEP Annual Exceedance Probability

ARR Australian Rainfall and Runoff

AWAP Australian Water Availability Project

BoM Bureau of Meteorology

CFT Climate Futures for Tasmania

FORGE Focussed Rainfall Growth Estimation

GCM Global Climate Model

IFHC Incremental Flood Hazard Category mAHD meters Australian Height Datum

SES State Emergency Services

1 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Glossary

Annual Exceedance Probability (AEP). The probability of equalling or exceeding a value in any given year. For example a 1 in 100 AEP flood has a 1 in 100 chance of being equalled or exceeded in any given year.

Annual Flood Series. A series of recorded annual maximum peak flood discharges.

Average Recurrence Interval (ARI). The average or expected value of the period between exceedances of a given discharge.

Climate Futures for Tasmania (CFT) Design Rainfall. Design rainfall generated by scaling current rainfalls to reflect the impacts of climate change.

Continuing Loss (CL). The average loss of rainfall per unit time to catchment depressions, infiltration, etc. during a storm event.

Flood Frequency Curve. A plot of a probability distribution fitted to a flood series.

Full Supply Level (FSL). Full supply level of a storage.

Gauging. The measurement of stream flow rate (cumecs or m3/s) at a given water level (stage).

Hydrograph. A plot of stream flow versus time. Generally refers to flood waves in a catchment.

Initial Loss (IL). The amount of precipitation lost to the catchment prior to runoff occurring.

The Australian Height Datum (AHD) is the reference level for defining reduced levels adopted by the National Mapping Council of Australia. The level of 0.0 m AHD is approximately mean sea level.

Rainfall Excess. The rainfall which directly contributes to flood runoff.

Rating. The relationship between stream flow (discharge) and river height (stage) for a particular river gauging site.

2 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

1. Introduction

A series of flood inundation maps has been produced for four representative catchments in Tasmania using projected proportional changes applied to design rainfalls estimated using the Focussed Rainfall Growth Estimation (FORGE) technique (Gamble and McConachy, 1999) and Australian Rainfall and Runoff (ARR) (Engineers Australia, 1999). The output of this study, for the State Emergency Services (SES), will provide valuable information on the future trend of flooding impacts as a result of projected changes to the climate. The impact of climate change on the intensity, duration and magnitude of flood events, and the subsequent changes to flood levels and extents were investigated. This report discusses the methods used to incorporate climate change projections within flood inundation maps and the effect of climate change on flood inundation for four catchments. Flood inundation maps have been developed for the baseline period (1961-1990) which incorporates historical data, and for three future periods (2010-2039, 2040-2069, and 2070-2099).

The following four catchments were used for this study:

Forth River;  Mersey River;  Huon River; and  Derwent River below Meadowbank.  These catchments were selected as they provide a good spatial representation of the state, they all flow through population centres, and they are of direct interest to the SES.

Design rainfall for annual exceedance probabilities (AEPs) of 10, 50, 100 and 200 years were developed in the Climate Futures for Tasmania (CFT) project. CFT is a collaborative research project that has generated high-resolution climate change projections for Tasmania. Dynamical downscaling was used to generate climate projections over Tasmania at a resolution of 0.1°.

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

2. Limitations of this Study

The design rainfall depths generated by CFT have some inherent uncertainties associated with them. This is detailed in full in White et al. (2010). Design rainfall depths did not show a consistent increase for the 21st century. It is likely that this is caused by natural variability swamping the climate signal in the earlier part of the century. In order to better isolate the impacts of climate change on design rainfalls from natural variability, the percentage change in rainfall between the end of the 21st century (2070-2099) and the baseline period was linearly scaled back. The climate signal-to-noise ratio is likely to be greatest at the end of the century. This resulted in a monotonic increase in the intensity of rainfall. This method has the effect of producing a conservative (greater) climate impact on the design rainfall for the period 2010-2069.

Assumptions pertaining to sea level rise are discussed further in Section 5.4 below. Sea level rise has been assumed to be consistently 0.8m for each of the future time periods.

Whilst it is recognised that storm-surge is likely to result in increased inundation risk for coastal areas, storm surge has not been taken into consideration for this study, as this study is limited to investigating the impacts of changes in the intensity, frequency and duration of rainfall events rather than on storm surge.

Discrepancies will exist between the base case flood inundation extents for this study and previous flood mapping studies. This will be due to differences in survey and terrain data sets used in the hydraulic modelling and flood mapping along with refinements made to hydrologic modelling parameters. This must be taken into account when interpreting the results of this analysis.

It should be noted that previous hydraulic studies completed for the four catchments were conducted for large events greater than the 1 in 100 and 1 in 200 AEP event. As such, in order to ensure stability of the hydraulic model for the Mersey, a baseflow of 100 m3/s from upstream of Parangana has been included in the model. This appears to have limited impact on downstream flood levels. This is discussed further in Section 5.6.1.

The hydraulic models and flood mapping have been based on the best information available. In the case of previous studies this was typically Department of Primary Industry, Parks, Water and Environment (DPIPWE) 5m and 10m contours and detailed river cross sections (obtained specifically for the study), however for the Mersey River DPIPWE LiDAR was used in the previous hydraulic models. For this study, where available, new DPIPWE LiDAR information has been used to better represent the ground topography for the purpose of mapping the flood inundation extents for rivers which were modelled using the 1-dimensional MIKE 11 hydraulic software package. For this study the Huon River was the only hydraulic model that was updated to make use of the new DPIPWE LiDAR which was used to replace the MIKE 21 grid previously derived from DPIPWE 10m contour information.

Through the validation process minor refinements were made to improve hydrological inputs. It should be noted that all hydrologic models used in this study have assumed storages are at full supply level (FSL).

The flood inundation extents derived from 1-dimensional hydraulic modelling have been plotted at cross section locations based on the geometry of the cross sections used in the MIKE 11 model and

5 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

the peak water levels predicted by the modeling. Between cross sections the flood inundation extents have been automatically interpolated using DPIPWE 1m LiDAR contours where available and DPIPWE 5m and 10m DPIPWE contours where LiDAR was not available. Where required manual edits were made to the flood inundation extents to resolve discrepancies between the different topographic data sets used in the hydraulic modeling and mapping. Due to time constraints and the large number of flood scenarios worked through for this project, it is likely that previous studies will have a more refined derivation of the flood extent line between cross sections.

6 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

3. Overview of Method

The following method was developed to adapt existing hydrologic models, hydraulic models and flood maps for use in mapping the change in flood levels resulting from climate change. The project has consisted of three main components: hydrologic modelling, hydraulic modelling and GIS mapping. The flow chart shown below illustrates the method used.

7 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

of Design Rainfalls Generation

design rainfalls generated by CFT were used to create a surface in GIS Gridded .

design rainfalls for each of the catchments was estimated from the GIS surfaces Mean .

percentage change in design rainfall was calculated between the baseline period and the end of the century The 21st .

and rainfall events by fitting a curve to the and percentage change in rainfall for each AEP Derived 12 hour 18 hour 24 hour, 48 hour 72 hour .

order to better isolate the impacts of climate change on design rainfalls the percentage change in rainfalls between the end of the century and In 21st baseline period were scaled back linearly periods were then derived the . Intermediate .

design rainfalls were factored to reflect the effect of climate change on rainfall intensities Current .

Modelling Hydrologic

pre• hydrologic models Sourced existing .

hydrologic models against pre• hydrological studies undertaken by Hydro Tasmania Validated existing .

Duration Analysis was undertaken to investigate whether or not the critical duration design flood for each of the catchments was likely to Critical as a result of climate change change

,QSXWVFDOHG&)7GHVLJQUDLQIDOOVWRK\GURORJLFPRGHOVDQGUDQPRGHOVWRJHQHUDWHIORRGK\GURJUDSKVGRZQVWUHDPRI+\GUR7DVPDQLDGDPV .

Frequency Analysis at key downstream locations for each of the catchments to account for pickup downstream of the hydrologic models Flood .

flood hydrographs created by the hydrologic model and scaled them to match the peak discharge derived from the flood frequency analysis Routed .

Modelling Hydraulic

– Hydraulic Model Flood – Hydraulic Model MIKE11 1 Dimensional MIKE 1 and 2 Dimensional

pre• hydraulic models Sourced existing

boundary conditions to reflect sea level rise boundary conditions to reflect sea level rise Changed . Changed .

model with hydrographs representing the design floods for the model with hydrographs generated from hydrologic models Ran Ran and three future periods the baseline and three future periods baseline representing .

Mapping GIS

information was sourced from DPIPWE LiDAR contours where possible this information was not available and Topographic 1m . When 5m 10m sourced from DPIPWE were used cross• on and contours and detailed survey where available previous contours . River sections (based 5m 10m ) from Tasmania internal projects were used Hydro .

critical duration flood for the baseline and the three future periods up to end of the st century were mapped levels at each of the cross• The 21 . Water were extracted from MIKE imported into GIS from which flood extents were derived areas around Latrobe and Huonville were sections 11 and . The using MIKE due to the availability of higher accuracy terrain data modelled 21 software .

Figure 3-1 Summary of method used

8 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

4. Hydrological Modelling

4.1 Modelling Approach

In developing hydrographs for the Mersey, Forth and Derwent a systematic stepwise process was adopted. The following discussion outlines the basic steps undertaken in this analysis.

1. The catchment areas and sub areas for the Mersey River Catchment, the Forth River

Catchment, the Derwent River Catchment and the Huon River Catchment were obtained from previous studies (Smythe, 2001(a); Smythe, 2001(b)).

2. The rainfall/runoff routing network for each of the catchments was sourced from previous

studies, along with the non linearity exponent and the loss parameters for design (Smythe, 2001(a), Smythe, 2001(b)).

3. The non linearity exponent for the river reach routing was assumed as 0.8, in line with the

current best practice recommendations (Pilgrim 1999).

The peak discharges for the Huon were developed using the Tasmanian Regional Flood Estimation technique. The shape of the adopted Huon hydrograph is derived from flood events gauged on the Huon River above Frying Pan Creek between 1948 and 1996.

Design rainfalls were estimated for the individual catchments. This was done by obtaining FORGE (focussed rainfall growth estimate technique) rainfalls and ARR99 design rainfalls when required, together with data from CFT pertaining to the percentage change in design rainfall depth between the baseline period and the three future periods.

All models created in this study have assumed storages are at full supply level (FSL).

4.2 Previous Projects

This project has utilised pre-existing hydrologic models to derive hydrographs for this report.

Smythe, C., 1995 Review of the Spillway Design Flood for Paloona Dam Hydro-Electric Commission Consulting Business Unit Water Resources Department Report No.: ENE-0004-30-01-CR-003

Smythe, C., 2001(a) Review of the Flood Hydrology for Parangana, Rowallan and Mackenzie Dams Hydro Tasmania Report No.: GEN-0309-CR-003.

Smythe, C., 2001(b) HEC Portfolio Risk Analysis: Hydrology – Spillway Re-assessment for Wilmot, Paloona, Parangana, Mackenzie, Liapootah, Wayatinah, Meadowbank Hydro Tasmania Report No.: GEN-0097-CR-10.

Knight, J., (2007) Huon Flood Evacuation Plan Hydro Tasmania Consulting Report Engagement Number.: E201709-Report-01

9 Climate Futures for Tasmania 25 February 2011

Wallis, M., (1995) Meadowbank Dambreak Study Volume 2 Hydrology. Dambreak Study Risk Analysis and Recommended IFF Hydro Electric Commission Civil Engineering Department Report No.: ENE- 0076-CR-001

4.3 Design Rainfalls

4.3.1 Design Rainfalls generated by CFT

The downscaled simulations of future climate reproduced the recent climate of Tasmania for temperature and rainfall. Multi-GCM ensemble simulations were found to provide more robust information than simulations from any single model (Meehl et al., 2007). For this study, the multi- GCM ensemble of the six downscaled GCMs has been used with an associated range of uncertainty for the future projections of the extremes; refer to Corney et al (2010) for further information.

White et al. (2010) adopted an automated Generalized Pareto distribution fitting procedure for the gridded observational and modelled climate simulations. The projected change to the frequency, magnitude and duration of extreme events as a result of the enhanced greenhouse effect was assessed by CFT and was used to inform this study. White et al. (2010) found significant changes to the magnitudes of extreme rainfall events, with the majority of the state displaying an increase in the intensity of rainfall at a given AEP by the end of the 21st century. The greatest increase in rainfall intensities is projected to occur in the north-eastern region of the state. The broad consistency between AEP estimates from the Australian Water Availability Project (AWAP) gridded observational dataset (Jones et al., 2009) and those from the CFT simulations for the reference period provide confidence that the future projections are plausible (White et al., 2010).

CFT generated rainfall AEP estimates for the 1 in 10, 1 in 50, 1 in 100 and 1 in 200 year design floods for the 24-hr, 48-hr and 72-hr duration design storm events for a baseline period 1961-1990 and three future periods 2010-2039, 2040-2069 and 2070-2099. The percentage changes in the AEP design rainfall estimates were then calculated for each catchment of interest and this factor was applied to ARR99 and FORGE data.

4.3.2 Calculating Percentage Change in Rainfall from CFT Design Rainfall Inputs

The spatial distribution of Tasmanian Rainfall is not well represented by Global Climate Models because of their coarse spatial resolution (Figure 4-1). Previous studies of Tasmanian future climate have downscaled GCM projections either statistically (e.g. the Tasmania Sustainable Yields Project. see Post et al. 2009) or dynamically (e.g. Mckintosh et al. 2006). Statistical downscaling fixes historically derived relationships between climate and a given variable, such as rainfall. Statistical downscaling of GCM projections essentially assumes these relationships will be maintained into the future. Dynamical downscaling allows weather systems to vary according to our understanding of meteorology and atmospheric physics.

There is evidence that the weather systems that bring rain to Tasmania may change as the planet warms, altering the regional and seasonal character of Tasmanian rainfall (Grose et al. 2010). Whilst computationally expensive, dynamical downscaling accounts for changes to weather systems caused by global warming. The timing and duration of future rainfall events are free to vary.

10 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

CFT generated gridded design rainfall for AEPs of 1 in 10, 1 in 50, 1 in 100 and 1 in 200 years using dynamical downscaling at a resolution of 0.1° for three durations: 24 hours, 48 hours and 72 hours. This was completed for the baseline period (1961-1990) and three future periods extending out to the end of the 21st century (2010-2039, 2040-2069 and 2070-2099). In order to derive average design rainfalls for each of the four catchments of interest, a GIS surface was created from linearly interpolated gridded rainfall data (see Appendix A to view an example of the mean, 5% confidence interval and 95% confidence interval design rainfall surface for the 24 hour 1 in 100 AEP rainfall event).

The average design rainfall for each of the catchments was calculated within GIS, and proportional changes in rainfall were derived for the three future periods. Projected changes were found to not be uniform across the three future periods of 2010-2039, 2040-2069 and 2070-2099, suggesting that some areas may actually see a decrease in rainfall intensity for a given AEP in the latter part of the 21st century when compared against the 2040-2069 period (White et al., 2010).

Table 4-1 demonstrates the variability in projected changes for the 1 in 200 AEP event across the three future periods at selected locations across Tasmania. For example, Miena/Liawenee in the Central Highlands shows a marked reduction in projected rainfall during the middle part of the century (2040-2069) compared against the end of the century (2070-2099). It should be noted that this is consistent with the projected decline in annual rainfall over the central highlands (Grose et al., 2010). Dynamically downscaled 24-hour multi-GCM ensemble rainfall data was validated against the AWAP gridded dataset on an identical 0.1 degrees grid-resolution across the state as shown below in Table 4-1.

11 Climate Futures for Tasmania 25 February 2011

Location AWAP Change Against AWAP 1 in 200 AEP Multi-GCM Multi-GCM Multi-GCM (1961-1990) Ensemble ensemble ensemble (2010-2039) (2040-2069) (2070-2099) Hobart 100 (76/128) 31 [31%] 40 [40%] 30 [30%] Launceston 66 (51/85) 3 [4%] 34 [51%] 34 [52%] Devonport 97 (76/131) 4 [4%] 23 [24%] 36 [37%] Strathgordon 97 (93/105) 21 [21%] 30 [31%] 36 [37%] Miena/Liawanee 98 (78/134) 50 [51%] 30 [30%] 5 [5%]

(adapted from White et al., 2010)

Table 4-1 Design rainfall depths did not show a consistent increase for the 21st century

Table 4-1It is likely that the variability in rainfall across the three future periods is caused by natural variability swamping the climate signal in the earlier part of the century. In order to better isolate the impacts of climate change on design rainfalls from natural variability, the percentage change in rainfall between the end of the 21st century (2070-2099) and the baseline period was linearly scaled. This gives a monotonic increase in projected design rainfalls for the periods 2010-2039 and 2040- 2069. While the projections indicate that the intensity of rainfall is likely to increase in a non-linear fashion, with the largest change occurring at the end of the 21st century, the method that has been adopted for this study will provide a conservative (greater) estimate of the impact of climate change on flood inundation for the period 2010-2069. Figure 4-2 below shows the mean rainfall depth for the 24 hour duration event across all AEPs for each of the catchments for the baseline and future periods (2010-2099).

In order to undertake critical duration analysis the percentage change in rainfall for the 12 hour and 18 hour design event needed to be estimated. A relationship was found to exist between the durations of the rainfall events and their increase in rainfall intensity as a result of climate change. It was found that a power function (see Figure 4-3) could be fitted to the 24 hour, 48 hour and 72 hour storm event for each of the four catchments.

Figure 4-3 shows the percentage change in rainfall depth between the baseline period (1961-1990) and the end of the 21st century (2070-2099) for each of the four catchments being investigated. The plots show that the percentage change in rainfall depth will vary according to the duration of the rainfall event. Events with durations greater than 24 hours are projected to show an insignificant change.

12 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Forth Mersey

1:10 12hr Duration 1:10 18hr Duration 1:10 24hr Duration 1:10 48hr Duration 1:10 72hr Duration 250

t 200.0 p ) e 200 m D

l m l (

a ) 150.0

f 150 h t n m p i e a m ( D

R 100 l

l 100.0 a n f g n i i a s 50 R e

n D 50.0 g 0 i s e

1961-1990 2010-2039 2040-2069 2070-2099 D 0.0 Duration (hr) 1961-1990 2010-2039 2040-2069 2070-2099 Period 1:10 24hr Duration 1:50 24hr Duration 1:100 24hr Duration 1:200 24hr Duration

Huon Derwent

1:10 24hr Duration 1:50 24hr Duration 1:100 24hr Duration 1:200 24hr Duration 1:10 24hr Duration 1:50 24hr Duration 1:100 24hr Duration 1:200 24hr Duration

200.0 200.0 ) ) m m m m ( (

150.0 150.0 h h t t p p e e D D

l l l l 100.0 100.0 a a f f n n i i a a R R

n n 50.0 50.0 g g i i s s e e D D 0.0 0.0 1961-1990 2010-2039 2040-2069 2070-2099 1961-1990 2010-2039 2040-2069 2070-2099 Period Period

Figure 4-2 Mean rainfall depth for the 24 hour duration storm event between the baseline period and the end of the 21st century

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Forth Mersey

1:10 Design Rainfall 1:50 Design Rainfall 1:100 Design Rainfall 1:200 Design Rainfall 1:10 Design Rainfall 1:50 Design Rainfall 1:100 Design Rainfall 1:200 Design Rainfall

60% 60% 1:10 Design Rainfall 1:10 Design Rainfall -1.2741 ) y = 2.5646x-0.9496 ) y = 8.7308x

% % 2 ( R2 = 0.607 ( R = 0.7604

h 50% h 50% t 1:50 Design Rainfall t 1:50 Design Rainfall p p

e y = 7.0775x-1.223 e y = 21.436x-1.5523 D D

l R2 = 0.531 l 2 l l R = 0.7541 a a

f 40% f 40%

n 1:100 Design Rainfall n 1:100 Design Rainfall i i

a y = 8.6831x-1.2726 a y = 21.436x-1.5523

R R R2 = 0.5424 2

n n R = 0.7541 i i 30% 30% e 1:200 Design Rainfall e 1:200 Design Rainfall g g -1.7337

n y = 17.36x-1.4679 n y = 37.932x a a 2

h R2 = 0.6534 h R = 0.8668 C C

20% 20% e e g g a a t t n n e e

c 10% c 10% r r e e P P

0% 0% 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 Duration (hr) Duration (hr)

Huon Derwent

1:10 Design Rainfall 1:50 Design Rainfall 1:100 Design Rainfall 1:200 Design Rainfall 1:10 Design Rainfall 1:50 Design Rainfall 1:100 Design Rainfall 1:200 Design Rainfall

60% 60% 1:10 Design Rainfall 1:10 Design Rainfall -0.6707 ) y = 1.829x-0.6467 ) y = 1.2678x

% % 2 ( R2 = 0.9746 (

R = 0.8668

h 50% h 50% t 1:50 Design Rainfall t 1:50 Design Rainfall p p

e y = 2.5164x-0.7242 e y = 2.4054x-0.8585 D D

l R2 = 0.9665 l 2 l l R = 0.8668 a a

f 40% f 40%

n 1:100 Design Rainfall n 1:100 Design Rainfall i i

a y = 2.9249x-0.7607 a y = 4.6038x-1.039

R R R2 = 0.963 2

n n R = 0.9418 i i 30% 30% e 1:200 Design Rainfall e 1:200 Design Rainfall g g -1.0914 n y = 3.3227x-0.7852 n y = 5.7111x a R2 = 0.9864 a 2 h h R = 0.9388 C C

20% 20% e e g g a a t t n n e e

c 10% c 10% r r e e P P

0% 0% 0 10 20 30 40 50 60 70 80 0 20 40 60 80 100 120 140 Duration (hr) Duration of Storm Event (hr)

Figure 4-3 Percentage change in rainfall depth between the baseline period (1961-1990) and the end of the 21st century (2070-2099)

14 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

4.3.3 Australian Rainfall and Runoff and CRC-FORGE Rainfalls

The derivation of flood estimates in Tasmania has followed the Institution of Engineers Australia’s, publication of Australian Rainfall and Runoff, 1999 (ARR99). This text provides a guideline for flood estimation around Australia. Since its publication, new methods for determining regional rainfalls (FORGE) have been developed, as well as the development of new flood methodologies. Australian Rainfall and Runoff (2001) states that, “…in view of these considerations, firm guidance and specific design data have been included where possible. However, the document is not intended to be entirely prescriptive or a strict code of practice. Where circumstances warrant, designers have liberty, and perhaps a duty, to use other procedures and data. The use of new or improved procedures is encouraged, especially where these are more appropriate than the methods described in this publication. It is certain that within the effective life of the document, new procedures and design information will be developed. Where they are based on observed data or have been shown to reproduce its characteristics, these new methods should be used. Designers are also encouraged to critically evaluate the procedures presented herein, and any procedures developed subsequently, as befits any professional activity. The most appropriate approach for the particular set of circumstances should be adopted.”

The CRC-FORGE (Focussed Rainfall Growth Estimation) technique was developed at Monash University in the late 1990s. It is a statistical method for estimating probabilistic rainfall using regional data. It was initially applied to Victoria (Nandakumar et al., 1997) and has since been successfully applied to Tasmania (Gamble and McConachy, 1999).

Design rainfall estimates in the range of 1 in 50, 1 in 100 and 1 in 200 AEP for the catchment were determined as follows: 1. The FORGE procedure was used to derive design rainfall estimates for events of AEP 1 in 50 to

1 in 200 AEP events for the 24 hour, 48 hour and 72 hour durations. 2. Tasmanian FORGE areal reduction factors (ARFs) were implicitly applied to the FORGE rainfall

as part of the procedure. 3. The 1 in 10 design rainfall was calculated using Australian Rainfall and Runoff (ARR) (1999).

ARR99 design rainfalls are expressed in terms of point rainfall intensity, which is the rainfall depth (mm) at a location per hour. When estimating floods of large catchments, an estimate of the average areal rainfall intensity across the catchment is required. This is the mean rainfall depth per hour over the entire catchment. Areal reduction factors (ARF) for the catchment can be determined by the ratio of point rainfall intensities and average areal rainfall intensities. ARFs are applied to point rainfall depths, such as the 1 in 10 design rainfall generated by ARR99 to convert them to equivalent measurements for the whole catchment area. In this case the FORGE areal reduction factor was applied to the ARR99 design rainfalls.

4.3.4 Adopted Design Rainfalls

Design rainfalls for the baseline period were derived using various methods. Standard Forge design rainfalls were used to determine the 1 in 50, 1 in 100 and 1 in 200 AEP design rainfalls. ARR99 rainfalls were used to derive the 1 in 10 AEP design rainfalls. Unlike FORGE design rainfalls which are representative of the catchment, the ARR99 design rainfall generates a point rainfall which does not reflect the mean design rainfall over the entire catchment. To correct this, an areal adjustment factor was calculated. This was done by scaling the 1 in 50 and 1 in 100 design rainfalls from ARR99 to match the standard FORGE design rainfalls. The scaling factor was then applied to the ARR99 1 in 10

15 Climate Futures for Tasmania 25 February 2011

design rainfall to provide a design rainfall which better represented what was occurring over the entirety of the catchment.

For the future periods, the percentage change in rainfall derived from the linear interpolation between the rainfall intensities at the end of the 21st century (2070-2099) and the baseline period (1961-1990) were applied to the design rainfalls. The percentage change in rainfall was only available for the 24 hour, 48 hour and 72 hour flood durations. To extend this data to the 12 hour and 18 hour storm events a relationship between the duration of the event and the percentage change in rainfall was determined for each of the catchments. This is discussed in further detail in Section 4.3.2.

For the Forth, Huon and Derwent, the critical duration was found to be 24 hours or greater for all AEPs, however, for the Mersey the critical duration was projected to decrease from 24 hours to 18 hours under the A2 SRES climate scenario.

The design rainfalls are shown in Table 4-2, Table 4-3, Table 4-4 and Table 4-5. Colour coding has been used to identify the various subsets that make up the overall design rainfall and the methodologies attributed to these subsets:  Blue Standard Forge Rainfall

 Green ARR99 Rainfall factored up to fit Forge Rainfall Curve

 Red Future design rainfall calculated by applying CFT percentage change in rainfall

 Black Extrapolated 18hr duration rainfall depths

The design rainfall depths are summarised in Table 4-2, Table 4-3, Table 4-4 and Table 4-5. 

Table 4-2 Adopted Design Rainfall for the Forth River Catchment below Paloona (mm)

1961-1990 2010-2039 2040-2069 2070-2099 AEP (1:Y) 24 48 72 24 48 72 24 48 72 24 48 72 10 107 137 155 112 139 158 118 141 161 123 143 164 50 144 185 210 153 187 215 162 189 219 171 191 223 00 160 208 239 171 210 244 182 212 248 192 214 253 200 178 234 270 191 236 275 204 238 280 216 241 285

Table 4-3 Adopted Design Rainfall for the Mersey River Catchment below Parangana (mm)

1961-1990 2010-2039 2040-2069 2070-2099 AEP (1:Y) 18 24 48 72 18 24 48 72 18 24 48 72 18 24 48 72 10 95 109 139 158 102 115 141 161 109 122 143 164 115 129 144 166 50 134 153 201 228 144 163 203 231 153 172 205 234 163 182 207 237 100 148 169 222 254 159 180 224 257 169 190 226 260 180 201 228 264 200 165 188 247 282 177 200 249 285 167 211 251 289 200 222 254 292

16 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Table 4-4 Adopted Design Rainfall for Huon River Catchment below Judbury (mm)

1961-1990 2010-2039 2040-2069 2070-2099 AEP (1:Y) 24 48 72 24 48 72 24 48 72 24 48 72 10 79 106 118 85 111 123 92 115 127 98 120 132 50 120 167 198 131 174 206 141 182 214 152 190 222 100 133 187 222 145 196 231 157 205 240 169 214 249 200 147 211 251 161 221 261 175 231 271 188 242 281

Table 4-5 Adopted Design Rainfall for the Derwent River Catchment below Meadowbank (mm)

1961-1990 2010-2039 2040-2069 2070-2099 AEP (1:Y) 24 48 72 24 48 72 24 48 72 24 48 72 10 49 63 68 52 65 69 54 66 71 57 68 73 50 88 119 140 93 122 143 98 125 146 103 128 150 100 99 134 157 105 137 160 111 140 164 117 144 167 200 110 150 176 117 154 180 124 157 183 131 160 187

4.3.5 Design Temporal Patterns

The Bureau of Meteorology (BoM) previously provided one set of temporal patterns to Hydro Tasmania, the unsmoothed temporal patterns for 24, 36, 48 and 72 hour durations. These patterns were used with design rainfalls of AEPs more frequent than 1 in 200 (Engineers Australia, 1999).

4.3.6 Spatial Patterns

The BoM (1994) had previously supplied spatial patterns with the Generalised Southeast Australia Method (GSAM) Probable Maximum Precipitation (PMP) estimates. The spatial patterns provided implicitly account for topography. These patterns were used in the rainfall-runoff modelling component of this study. For the Mersey Catchment Model the spatial pattern was applied to Lake Parangana’s catchment.

4.4 Catchment Modelling

4.4.1 The Catchment Model

Rainfall/runoff-routing catchment models used in previous flood studies undertaken by Hydro Tasmania were used to model outflows from Parangana, Paloona and Meadowbank. These models were developed using Kisters Hydstra Model Builder. These models convert rainfall to runoff, considering initial and continuing losses in the catchment and river routing. No model was available for the Huon catchment for this study. Refer to Section 4.1 for more details regarding the derivation of hydrographs for the Huon.

17 Climate Futures for Tasmania 25 February 2011

4.4.2 Dam and Storage Characteristics

Of the four catchments investigated, three of the catchments (Mersey, Forth and Derwent) have significant upstream storages. The characteristics of the significant storages within each of the catchments are described in further detail in Table 4-6.

Table 4-6 Storage Characteristic Data

Mersey River Catchment Derwent River Forth River Catchment Catchment Parangana Mackenzie Rowallan Meadowbank Paloona Catchment Area (km2) 712 351 78 - 778.9 Normal Minimum 378.87 466.65 1111.00 67.060 49.07 Operating Level (NMOL) (m, AHD) (m) Full Supply Level (FSL) 381.00 487.68 1120.75 73.150 53.34 (m, AHD) (m) Design Flood Level (DFL) 386.18 490.88 1122.24 79.000 61.14 (m, AHD) (m) Dam Crest Level (m, 387.40 492.25 1122.27 - 61.87 AHD) (m) Freeboard to dam crest 1.22 1.37 0.03 - 0.73 (from existing DFL) (m) Spillway Design Capacity 2167 637 537 - 2040 (m3/s) Lake Surface Area at FSL 1.14 8.86 2.96 - 1.78 (km2) Ratio of Lake Area to 1.14 8.86 3.8 - 0.23 Catchment Area (%) Gross Storage Capacity - - - - 19.14 at FSL (Mm3) Effective Storage 2.29 121.41 18.97 - 6.806 Capacity at FSL (Mm3)

4.4.3 Variation in losses with AEP for the design analysis

As recommended in ARR Book VI, Section 4.3, the design losses were varied logarithmically against AEP from the calibrated values. The calibrated loss values were used for AEPs more frequent than 1 in 100 and losses were varied from these values down to 0.1 for the AEP of the PMP.

Table 4-7 below shows the variation of initial and continuing loss with AEP for the Mersey River, Derwent River and Forth River.

18 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Table 4-7 Variation of Initial and Continuing Loss with AEP

Mersey River Catchment Derwent River Forth River Catchment Catchment Parangana Rowallan Mackenzie Meadowbank Paloona AEP IL CL IL CL IL CL IL CL IL CL (1:Y) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) 10 30 5.5 25 2.5 0.1 5 12 0.2 30 2.5 50 30 5.5 25 2.5 0.1 5 12 0.2 30 2.5 100 30 5.5 25 2.5 0.1 5 12 0.2 30 2.5 200 19.53 4.07 16.5 1.96 0.1 3.72 7.2 0.19 30 0.4

4.4.4 Validation of Catchment Model

4.4.5 The Design Model

The design version of the calibrated Kisters Hydstra Model Builder rainfall/runoff models were modified to run the 1 in 10, 1 in 50, 1 in 100 and 1 in 200 AEP design floods for the critical duration.

For the Mersey River Catchment the Lemonthyme, Fisher and Rowallan power stations were all assumed to not be operating during the entire flood event. For the purpose of analysis outflow was assumed to occur via the spillway of each dam. Baseflow was assessed as part of the calibration process and it was considered that for independent design events, zero baseflow was appropriate.

(Smythe, 2001(a))

For the Forth River Catchment the powerstations were all assumed to not be operating during the entire flood event. For the purpose of analysis outflow was assumed to occur via the spillway of each dam. Baseflow was assessed as part of the calibration process and it was considered that for independent design events, zero baseflow was appropriate.

(Smythe, 2001(b))

For the Derwent River Catchment the powerstations were all assumed to not be operating during the entire flood event. For the purpose of analysis outflow was assumed to occur via the spillway of each dam. Baseflow was assessed as part of the calibration process and it was considered that for independent design events, the following subcatchments would contribute baseflow:

Table 4-8 Baseflow into the Derwent River Catchment

Subcatchment Baseflow (m3/s) Lake Echo 21.1 Dee 6.3

(Smythe, 2001(b))

19 Climate Futures for Tasmania 25 February 2011

Hydrographs generated for the Huon were developed using the Tasmanian Regional Flood Estimation technique. The shape of the adopted Huon hydrograph is derived from flood events gauged on the Huon River above Frying Pan Creek between 1948 and 1996. Hydrographs for the future scenarios have been scaled based on an AEP ratio determined for the Mersey and the Forth, refer to Section 4.8.

4.5 Results for Design Flood Events

4.5.1 Critical Duration of the Outflow Flood

Critical durations were analysed for the four catchments. This analysis was undertaken with the aim of identifying the critical duration of storm event which gives the highest peak flow, and to determine whether the critical duration would be likely to change as a result of climate change. Previous studies provided indications of the critical duration event for inflows and outflows to major storages in each of the catchments for the baseline period of 1961-1990. These are shown in Table 4-9.

Table 4-9 Critical Outflow and Inflow Durations

Critical Outflow Duration Critical Inflow Duration Mersey River Catchment DS Parangana 24/18 hours 24/18 hours Forth River Catchment DS Paloona 24 hours 24 hours

*1Derwent River Catchment DS 120 hours 120 hours Meadowbank Huon River Catchment DS Judbury 72 hours 72 hours

Analysis of the Mersey River Catchment for the baseline period shows that the catchment has a critical duration of 24 hours. However, for the 2010-2039 period the critical duration is 18 hours, with the exception of the 1 in 10 AEP which remains at 24 hours. For the 2040-2069 and 2070-2099 periods the critical durations for all AEPs were found to be 18 hours. This finding is supported by the distribution of percentage change in rainfall which indicates that climate change will substantially increase the intensity of short duration rainfall events, and conversely will show only a limited impact on the intensity of rainfall events with durations in excess of 24 hours. Figure 4-4 below shows percentage change in the outflow flood from Lake Parangana between the baseline and the end of the 21st century (2070-2099).

1 Note: Critical durations for the outflows to the Derwent River Catchment Downstream of Meadowbank were at 120 hours for all AEPs. At longer duration rainfall were not available, thus the critical duration may exceed 120 hours.

20 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

1-10 AEP 1-50 AEP 1-100 AEP 1-200 AEP

160%

140% a n a g n a

r 120% a P

m o

r 100% f

w o l f t

u 80% O

n i

e g

n 60% a h C

g 40% a t n e c r

e 20% P

0% 0 12 24 36 48 60 72 Duration (hr)

Figure 4-4 Percentage change in Outflow Flood between 2070-2099 and the baseline period for the Mersey

Analysis of the Forth River Catchment for the baseline period shows that the catchment has a critical duration of 24 hours. Investigations were undertaken to determine whether or not the critical duration would remain at 24 hours under climate change. This study has found that the change in rainfall as a result of climate change is most significant for short duration events, i.e. shorter duration events will show the greatest increase in intensity, while long duration events in excess of 24 hours will show little change. Figure 4-5 below shows the percentage change in the outflow flood between the baseline and the end of the 21st century (2070-2099) for the Forth.

21 Climate Futures for Tasmania 25 February 2011

35% ) %

( 30%

h t p e D

l 25% a f n i a R

n 20% g i s e D

n i 15% e g n a h C

e 10% g a t n e c r

e 5% P

0% 0 12 24 36 48 60 72 Duration (hr)

1:10 AEP 2070-2099 1:50 AEP 2070-2099 1:100 AEP 2070-2099 1:200 AEP 2070-2099

Figure 4-5 Percentage change in Outflow Flood between 2070-2099 and the baseline period for the Forth

Previous analysis of the Huon River Catchment for the baseline period shows that the catchment has a critical duration of 72 hours (Smythe, 2001b). Analysis of the Forth and the Mersey Catchments which were found to have critical durations of 24 hours, allowed us to assume that like the Forth and the Mersey, the critical duration of a flood event on the Huon River would remain stable.

Analysis of the Derwent River Catchment for the baseline period shows that the catchment has a critical duration of 120 hours, which is unchanged under future climate. Prior to this study, flood mapping on these catchments had not investigated storm events with durations greater than 24 hours, as no rainfall data was available. However, the 96 hour and 120 hour design rainfalls are now available using FORGE. This analysis found that the impacts of climate change are considered to be negligible for long duration events. Where the critical event duration is in excess of 24 hours, the percentage increase in rainfall will be well within the errors in the original estimate of design rainfalls, the rainfall-runoff modelling and the hydraulic modelling. The long duration response for the Derwent catchment, caused by a large catchment and significant upstream storages, acts to mitigate the impact of climate change on flood levels in the Derwent River below Meadowbank.

The following conclusions have been drawn based on the above study. (i) Catchments which have a critical duration of greater than 72 hours are unlikely to see

any significant increases in rainfall as a result of climate change projected using these models under the A2 SRES emissions scenario and as such it can be assumed that the critical duration will remain stationary. (ii) Catchments with a critical duration less than 24 hours will see significant proportional

increases in rainfall and as such the critical duration will be more likely to lessen.

22 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

4.6 Comparison against Previous Studies

Studies of the hydrology for the Mersey, Forth, Huon, and Derwent have been undertaken by Entura in the past. Table 4-10 summarises the 1 in 100 AEP design flood for this analysis and in previous analyses for each of the catchments for the baseline period.

Table 4-10 Comparison with the previous results for the 1 in 100 AEP design flood

Catchment Reference to Discharge from Hydrologic Model Previous Study This Study Previous Study % Difference Design Design Design Design Design Design Inflow Outflow Inflow Outflow Inflow Outflow (m3/s) (m3/s) (m3/s) (m3/s) (%) (%) Mersey Smythe 591 556 591 566 0.0 1.8 (2001) Smythe 587 546 1011 949 72.2 73.8 Forth2 (2001) Derwent3 Smythe 2614 2525 2502 2403 -4.3 -4.8 (2001) Huon4 NA 2653 2653 2653 2653 0.0 0.0

4.7 Flood Frequency Analysis

Catchment pickup between the site modelled by the hydrologic model and the point of input to the hydraulic model needed to be estimated. Pickup was determined by undertaking flood frequency analysis at the downstream site location and scaling the hydrograph generated by the hydrologic model to reflect both routing and pickup from the downstream catchment area. Flood frequency curves were generated using a Log Pearson Type III or GEV distribution fitted to annual maxima data sourced from the selected gauging sites. Refer to the table below to see a summary of the results. Appendix B contains the flood frequency curves which have been fitted to each of the catchments of interest.

2 Prior Forth model used a continuing loss factor of 0.4mm instead of the 2.5mm which was found to be appropriate for the flood events less than the 1 in 100 flood event. 3 The Derwent catchment was found to have a critical duration of at least 120 hours. 120 hours has been used for the current modelling, prior modelling assumed a critical duration of 72 hours. 4 The hydrographs generated for the Huon were directly inserted into the hydraulic model for the baseline scenario. Hydrographs for the future scenarios have been scaled based on an AEP ratio determined for the Mersey and the Forth, refer to Section 4.8.

23 Climate Futures for Tasmania 25 February 2011

Table 4-11 Details of Flood Frequency Analysis

Gauging Site Distribution Period of Peak Discharge from Flood Frequency Analysis Record 1 in 10 1 in 50 1 in 100 1 in 200 AEP AEP AEP (m3/s) AEP (m3/s) (m3/s) (m3/s) Mersey River at GEV 31 505 1095 1565 2270 Latrobe Forth River at GEV 36 455 720 880 1075 Wilmot Huon River at GEV 48 1950 2445 2650 2860 Judbury Derwent River at LPIII 37 1490 2515 3050 3650 Macquarie Plains

4.8 Hydrographs

Discharges from the hydrologic models were routed downstream and the inflows to the hydrologic model were scaled such that the peak flow at the nominated downstream site matched the peak flow indicated in the flood frequency curve. This was calculated using the following equation.     Flow RoutedFlow Factor GS Inflow Where:  Factor is the scaling factor, where the inflow is factored such that the downstream flow is

equal to the peak discharge estimated using the flood frequency analysis.  Flow is the flow at the gauging station GS  RoutedFlow is the discharge from the hydrologic model which has been routed to the

downstream gauging site.

As no previous hydrologic study was available for the Huon river, hydrographs for the Huon River at Judbury were scaled based on a derived relationship between the percentage change in rainfall and the percentage change in runoff for the Mersey and the Forth. This was done for each AEP. Refer to Figure 4-6 to view plots of the percentage change in runoff versus the percentage change in design rainfall for the Mersey and Forth catchments.

A separate scaling factor was found for each catchment and each AEP, as shown below in Table 4-12. Pickup downstream of Hydro Tasmania’s storages was estimated by fitting the flood hydrograph to the flood peak estimated at the downstream site, using the results of the flood frequency analysis.

Table 4-12 Scaling Factors used in deriving flood hydrographs

24 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

1 in 10 AEP 1 in 50 AEP 1 in 100 AEP 1 in 200 AEP Mersey River at 4.47 2.30 2.60 2.37 Latrobe Forth River at 2.54 1.70 1.31 0.44 Wilmot Derwent River at 0.04 0.87 1.52 1.98 Macquarie Plains

These hydrographs were used as inputs to hydraulic models, which are discussed in further detail below. Refer to Appendix C below to view hydrographs for each of the four catchments. Hydrographs for the three future periods used the same scaling factor as those used for scaling the baseline period.

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

1 in 10 AEP Flood y = 4.3133x 1 in 50 AEP Flood R2 = 0.8849 1.0 1.0 y = 2.8583x 0.9 0.9 R2 = 0.9737 f f 0.8 f

f 0.8 o o n n u

0.7 u

R 0.7 R

n i n i

0.6

e 0.6 e g g n n

a 0.5 a 0.5 h h C C

e 0.4 e 0.4 g g a a t t

n 0.3 n

e 0.3 e c c r r e

0.2 e

P 0.2 P

0.1 0.1

- - - 0.05 0.10 0.15 0.20 0.25 - 0.05 0.10 0.15 0.20 0.25 Percentage Change in Rainfall Percentage Change in Rainfall

1 in 100 AEP Flood 1 in 200 AEP Flood y = 1.9692x - 0.004 y = 2.603x R2 = 0.9982 R2 = 0.9831 1.0 1.0

0.9 0.9 f f f f 0.8 0.8 o o n n u u 0.7 0.7 R R

n n i i

0.6 0.6 e e g g n n a a 0.5 0.5 h h C C

e e 0.4 0.4 g g a a t t n n 0.3 0.3 e e c c r r e e 0.2 0.2 P P

0.1 0.1

- - - 0.05 0.10 0.15 0.20 0.25 - 0.05 0.10 0.15 0.20 0.25 Percentage Change in Rainfall Percentage Change in Rainfall

Figure 4-6 Percentage change in runoff versus percentage change in design rainfall for the Mersey and the Forth catchments.

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

5. Hydraulic Modelling

Pre-existing MIKE 11 and MIKE 21 hydraulic models were used to generate flood levels over the areas of interest for the baseline case (1961-1990) and the three future climate periods (2010-2039, 2040- 2069 and 2070-2099).

5.1 Previous Studies

Hydraulic models for each of the four catchments were drawn from the following flood studies for use in this project:

Knight, J., (2007) Huon Flood Evacuation Plan, Hydro Tasmania Consulting, Report Number: E201709- Report-01

Barker, G., (2001) Parangana Dambreak Study, Hydro Tasmania Consulting, Report Number: GEN- 105470-CR-001

Birch, E., (2007) Portfolio Risk Assessment Engineering Assessments the Mersey Forth Dams: Paloona, Parangana, Mackenzie, Wilmot, Cethana, Devils Gate and Rowallan, Hydro Tasmania Consulting, Report Number: GEN-0097-CR-09

Li, S., Gerke, D., Herweynen, R., Morse, A., Sheedy, J., Wallis, M., and White, F., (1995) Meadowbank Dambreak Study, Hydro Electric Commission, Report Number: ENE-0076-CR-001

5.2 Storm Surge

Whilst it is recognised that storm surge is likely to result in increased inundation risk for coastal areas, storm surge has not been taken into consideration for this study, as this study is investigating the impacts of changes in the intensity, frequency and duration of precipitation events not on storm surge.

5.3 Sea level

5.3.1 Baseline

The sea levels adopted for the hydraulic models as tail water conditions were retained from the previous studies and were applied as fixed water levels for the modelled scenarios. The levels are provided in Error! Reference source not found. below along with relevant tide levels from the nearest port provided by the National Tidal Centre (2010).

Table 5-1 Base Case Sea Level

29 Climate Futures for Tasmania 25 February 2011

River Adopted Sea Closest Port MSL MHWS HAT Level (mAHD) (mAHD) (mAHD) (mAHD) Mersey River 2.0 Mersey River -0.011 1.296 1.659 (Devonport) Forth River 2.0 Mersey River -0.011 1.296 1.659 (Devonport) Huon River 0.8 Hobart 0.062 0.685 0.872 Derwent River 0.8 Hobart 0.062 0.685 0.872

Adapted from National Tidal Centre (2010)

5.4 Sea Level Rise

Sea level rise was incorporated into the hydraulic models. This study has assumed a 0.8m rise in sea level by the end of the 21st century. The Intergovernmental Panel on Climate Change (IPCC) reported that the upper limit of sea level rise is projected to be 0.8m by 2100 (IPCC, 2007). This estimate is inclusive of a provision of 0.2m to take into account the projected extent of ice sheet melt to that time. On the basis of these projections and in the absence of national benchmarks for coastal vulnerability, both the Victorian Coastal Council (2008) and the Queensland Department of Environment and Resource Management (2009) have established policies of planning for sea level rise of not less than 0.8m by 2100.

In the absence of further information, this study has applied a 0.8m sea level rise to each of the periods under review with the exception of the baseline period. The sea levels adopted for this study are shown in Table 5-2.

Table 5-2 Adopted Sea Level

River Adopted Sea Level (mAHD) Adopted Sea Level under Climate Change (mAHD) Mersey River 2.0 2.8 Forth River 2.0 2.8 Huon River 0.8 1.6 Derwent River 0.8 1.6

5.5 Tributary Effects

Flooding within tributaries of the modelled rivers is not covered in this report. Flooding along the four rivers has been modelled taking into account of discharges from all tributaries but hydraulic modelling and mapping of the tributaries has not been carried out.

30 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

5.6 Hydraulic Model

5.6.1 Mersey River Model

Hydraulic modelling was carried out for four flood AEPs and for four time periods. A summary of each of the flood scenarios modelled is provided Figure 5-1which shows the peak design discharge at the Latrobe flood gauge

10 AEP 50 AEP 100 AEP 200 AEP

3500

3000

2500 ) s / 3

m 2000 (

e t a R 1500 w o l F 1000

500

0 1961-1990 2010-2039 2040-2069 2070-2099 Period

Figure 5-1 Modelled Scenarios

The Mersey River hydraulic model is outlined below:  Combined MIKE 11 and MIKE 21 unsteady hydrodynamic model.

 MIKE 21 model based on 5m fixed spacing grid, derived from DPIWPE LiDAR, covering the

township of Latrobe.  MIKE 11 model based on DPIPWE 5m and 10m contour information and detailed river cross

section survey extending from Parangana Dam to the ocean.  The following changes were made to the previously developed model for this study:

Inclusion of 100m3/s baseflow approximately 90km downstream of Parangana Dam for

o model stability. Dambreak structures disabled. o Inflow hydrograph locations modified. o Inflow hydrographs modified for climate change scenarios. o Sea level boundary condition modified for climate change scenarios. o Refer to the previous study report for details of the Mersey River hydraulic model.

31 Climate Futures for Tasmania 25 February 2011

5.6.2 Forth River Model

Hydraulic modelling was carried out for four flood AEPs and for four time periods. A summary of each of the flood scenarios modelled is provided in Figure 5-2 which shows the peak discharge at the Forth River flood gauge located downstream of where the Wilmot River joins the Forth River.

10 50 100 200

1,800

1,600

1,400

) 1,200 s / 3 m (

1,000 e

g r a 800 h c s i

D 600

400

200

0 1961-1990 2010-2039 2040-2069 2070-2099 Period Figure 5-2 Modelled Scenarios

The Forth River hydraulic model is outlined below:  MIKE 11 model based on DPIPWE 5m and 10m contour information and detailed river cross

section survey extending from Cethana Dam to the ocean.  The following changes were made to the previously developed model for this study:

Dambreak structures disabled. o Inflow hydrograph locations modified. o Inflow hydrographs modified for climate change scenarios. o Sea level boundary condition modified for climate change scenarios. o Refer to the previous study report for details of the Forth River hydraulic model.

5.6.3 Huon River Model

Hydraulic modelling was carried out for four flood AEPs and for four time periods. A summary of each of the flood scenarios modelled is provided in Figure 5-3 which shows the peak design discharge at the Judbury flood gauge which is located at the Judbury bridge..

32 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

4,500

4,000

3,500

) 3,000 s / 3 m (

2,500 e g r a 2,000 h

c s i

D 1,500

1,000

500

0 1961-1990 2010-2039 2040-2069 2070-2099 Period

1:10 AEP 1:50 AEP 1:100 AEP 1:200 AEP

Figure 5-3 Modelled Scenarios

The Huon River hydraulic model is outlined below:  MIKE 11 model based on DPIWPE LiDAR data, DPIPWE 5m and 10m contour information and

detailed river cross section survey extending from Scotts Peak Dam to the ocean.  The following changes were made to the previously developed model for this study:

Cross sections within Huonville were updated to incorporate available DPIPWE 1m LiDAR

o data. Dambreak structures disabled. o Inflow hydrograph locations modified. o Inflow hydrographs modified for climate change scenarios. o Sea level boundary condition modified for climate change scenarios. o Refer to the previous study report for details of the Huon River hydraulic model.

5.6.4 Derwent River Model

Hydraulic modelling was carried out for four flood AEPs for the baseline period. Hydrologic modelling found that climate change would have a negligible impact on the flood hydrographs for the Derwent due to the critical duration of the catchment (120 hours), the size of the catchment and the presence of significant upstream storages. However, sea level rise resulting from climate change is still seen as a concern and this has been modelled and mapped. A summary of each of the flood scenarios modelled is provided in Figure 5-4 which shows the peak design discharge at New Norfolk.

33 Climate Futures for Tasmania 25 February 2011

10 50 100 200 4,000

3,500

3,000 ) s / 3 2,500 m (

g 2,000

r a h

c 1,500 s i D 1,000

500

- 1961-1990 Period

Figure 5-4 Modelled Scenarios

The Derwent River hydraulic model is outlined below:  MIKE 11 model based on DPIPWE 5m and 10m contour information and detailed river cross

section survey extending from Meadowbank Dam to just downstream of the Bridgewater Bridge.  The following changes were made to the previously developed model for this study:

5.7 Flood Modelling Results

Results from the hydraulic modelling indicate that changes to the maximum discharge during flood events will be proportional to the change in design rainfall.

Figure 5-5, Figure 5-6, Figure 5-7 and Figure 5-8 show that the change in flood levels between the baseline period and the end of the 21st century.

Flood levels at downstream chainages are affected by both sea level rise and changes in flow.

The 100 m3/s baseflow included in the Mersey River model had a limited impact on downstream flood levels, with the greatest impact occurring for the 1 in 10 AEP flood event.

34 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

No significant changes to water levels occur in the Derwent catchment below Meadowbank for the critical 120 hour events as a result of increasing rainfall intensities. It should be noted that a sea level rise of 0.8m will result in increased inundation in the lower reaches of the Derwent River. Figure 5-8 below shows the predicted change in water levels projected due to rising sea level.

Refer to Appendix E to view the modelled changes in water levels.

35 Climate Futures for Tasmania 25 February 2011

1:10 AEP 1:50 AEP 1:100 AEP 1:200 AEP

- 1.6 0

7 e 0 n 2

i ( 1.4 l e y r s u a t B n

1.2 e n C e

e t s

w 1.0 t 1 ) e 2

m b e (

l h ) e t

9 0.8

v f 9

e o 0

L 2

d r

n 0.6 e t e

a e W h

0.4 n i d

n e a g

n d 0.2 a o i h r C e

P 0.0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7 6 8 0 3 8 8 1 4 8 5 0 5 7 3 1 8 9 5 5 4 0 9 0 0 7 6 1 3 5 2 5 9 6 8 2 5 5 5 8 0 3 6 0 8 9 1 2 9 1 1 7 9 9 9 0 0 0 1 1 2 2 2 2 2 3 3 3 4 4 5 7 8 9 0 0 8 8 8 8 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 1 1 Chainage (m)

Figure 5-5 Change in water level between the baseline period and the three future periods for the Mersey River downstream of Parangana Dam

36 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

1:10 AEP 1:50 AEP 1:100 AEP 1:200 AEP

2.0 - 0

7 e

0 1.8 n 2 i ( l e y r

s 1.6 u a t B n

n 1.4 C e

e t s w t 1

) 1.2 e 2

m b e (

l h )

e t 1.0 9

v f 9 e o 0

L 2

r 0.8 n e t e

a e 0.6 W h

n i d

n e 0.4 a g

n d a o i

h 0.2 r C e P 0.0 30870 31700 33320 35270 36100 38510 39230 40040 41970 43680 44580 45880 46880 47200 Chainage (m)

Figure 5-6 Change in water level between the baseline period and the three future periods for the Forth River downstream of Paloona Dam

37 Climate Futures for Tasmania 25 February 2011

1:10 AEP 1:50 AEP 1:100 AEP 1:200 AEP

3.0 - 0

7 e 0 n 2 i ( l 2.5 e y r s u a t B n

e n C e

2.0 e t s w t 1 ) e 2

m b e (

l h ) e t

9 1.5

v f 9 e o 0

L 2

d r n e t e

a 1.0 e W h

n i d

n e a g 0.5 n d a o i h r C e P 0.0 81318 84713 87371 90870 95851 96946 100333 102101 104204 106250 107900 Chainage (m)

Figure 5-7 Change in water level between the baseline period and the three future periods for the Huon River downstream of Judbury

38 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

1:10 AEP 1:50 AEP 1:100 AEP 1:200 AEP

- 0.9 0

7 e 0 n 2

i ( 0.8 l e y r s u a

t 0.7 B n

e n C e

e t 0.6 s w t 1 ) e 2

m b 0.5 e (

l h ) e t 9

v f 9 e o 0 0.4

L 2

d r n e t e

0.3 a e W h

n i d 0.2

n e a g

n d 0.1 a o i h r C e

P 0.0 9 5 6 8 5 0 0 1 9 2 9 8 1 8 9 0 7 9 2 3 2 5 4 7 4 9 2 9 9 9 0 1 3 4 0 5 9 0 3 7 0 0 8 7 5 1 5 2 2 9 0 6 1 9 3 6 9 2 5 9 2 4 1 7 4 1 9 2 1 1 4 5 1 5 4 6 6 7 7 8 8 8 9 9 9 0 0 1 1 2 3 5 8 1 3 4 5 6 6 7 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 6 6 6 6 6 6 6 Chainage (m)

Figure 5-8 Change in water levels between the baseline period and the three future periods for the Derwent River downstream of Meadowbank Dam

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

6. Flood Mapping

Flood mapping using the results from the MIKE 11 and MIKE 21 hydraulic models was carried out to estimate flood extents for the baseline case and the three future periods.

The one-dimensional (MIKE 11) modelling produced flood height estimates at each cross section location for each of the flood events. Straight line interpolation between each cross section was performed, with the flood extent formed from the intersection of the modelled terrain and the interpolated surface. The terrain was modelled using Department of Primary Industries, Parks, Water and Environment (DPIPWE) LiDAR (Light Detection And Ranging) contour information where available and DPIPWE 5m and 10m (from 1:25000 topographical maps) contour information elsewhere. The intersecting line was created and smoothed using tools within the ArcMap 3D Analyst software.

The two-dimensional (MIKE 21) modelling in the Latrobe and Huonville areas produced ASCII grids of water depth which were converted and plotted using ArcGIS. The inundation extent line is formed where the water depth equals zero.

The following flood inundation maps are provided in Appendix XX:  Climate Futures Modelling – Mersey River:

1:10 Annual Exceedance Probability (AEP) Flood o 1:50 Annual Exceedance Probability (AEP) Flood o 1:100 Annual Exceedance Probability (AEP) Flood o 1:200 Annual Exceedance Probability (AEP) Flood o  Climate Futures Modelling – Forth River:

1:10 Annual Exceedance Probability (AEP) Flood o 1:50 Annual Exceedance Probability (AEP) Flood o 1:100 Annual Exceedance Probability (AEP) Flood o

41 Climate Futures for Tasmania 25 February 2011CPROPERTY ReportDate \* MERGEFORMAT |25 February 2011}

1:200 Annual Exceedance Probability (AEP) Flood o  Refer to Appendix D to view hard copies of the flood maps.

42 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

7. Conclusion

Flood inundation maps have been developed for a baseline period of (1961-1990) which incorporates historical data and for three future periods (2010-2039, 2040-2069, and 2070-2099) which incorporate the projected impact of climate change on rainfall and sea levels for the following Tasmanian river catchments:  Forth River

 Mersey River

 Huon River

 Derwent River.

These catchments were selected as they provide a good spatial representation of the state, they all flow through population centres, and they are of direct interest to the SES.

Projected proportional changes in rainfall due to climate change were estimated for each future period by dynamically downscaling global climate model simulations over Tasmania. These changes were applied to design rainfalls estimated using the Focussed Rainfall Growth Estimation (FORGE) technique (Gamble and McConachy, 1999) and Australian Rainfall and Runoff (ARR) (Engineers Australia, 1999).

Sea level rise due to climate change was assumed to be 0.8m above that of the baseline period for the three future periods. The Intergovernmental Panel on Climate Change (IPCC) reported that the upper limit of sea level rise is projected to be 0.8m by 2100 (IPCC, 2007). This estimate is inclusive of a provision of 0.2m to take into account the projected extent of ice sheet melt to that time. On the basis of these projections and in the absence of national benchmarks for coastal vulnerability, both the Victoria Coastal Council (2008) and Queensland Department of Environment and Resource Management (2009) have established policies of planning for sea level rise of not less than 0.8m by 2100.

Estimates of the percentage change in rainfall between the baseline period and the end of the 21st century indicates that climate change will substantially increase the intensity of short duration rainfall events, and conversely will show only a limited impact on the intensity of rainfall events with durations in excess of 24 hours. Spatially, the greatest increase in rainfall intensities is projected to occur in the north-eastern region of the state.

Inundation maps developed during this study have shown that climate change impacts on flood inundation can be captured at the local and regional scale using design rainfalls generated by high- resolution dynamical downscaling of GCMs.

Through the undertaking of a critical duration analysis for the four catchments, it has been found that catchments that have significant upstream storages and critical durations of 72 hours or greater are unlikely to be significantly impacted by climate change. Conversely, the intensity and frequency of events less than 72 hours duration were found to increase by the end of the century. It is recommended that efforts to gauge the impact of climate change on flood inundation should be focused on catchments which have minimal upstream storages and have critical durations less than

43 Climate Futures for Tasmania Revision No: 0 25 February 2011

72 hours. It was found that while the critical duration of flood events for the Mersey moved from 24 hours to 18 hours the difference in flood peak between the two durations was less than five percent and as such the critical duration was kept at 24 hours for the future flood scenarios to enable a direct comparison in flood levels. The critical duration was found to remain stable for the other catchments.

The flood peak was found to increase in a manner proportional to the percentage change in rainfall.

Flood levels are shown to be impacted predominately by changes in the design rainfall for river reaches outside of tidal influence. However, downstream sites are more significantly impacted by the anticipated rise in sea level at the end of the 21st century.

Although storm surge was not incorporated into this study, increased coastal flooding was evident as a result of sea level rise.

44 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

8. Acknowledgements

The Climate Futures for Tasmania project was funded primarily by the State Government of Tasmania, the Australian Government’s Commonwealth Environment Research Facilities Program and Natural Disaster Mitigation Program. The project also received additional funding support from Hydro Tasmania.

Scientific leadership and contributions were made from a consortium of organisations including: Antarctic Climate & Ecosystems Cooperative Research Centre, Tasmania Department of Primary Industries, Parks, Water and the Environment, Tasmanian State Emergency Service, Entura (formerly Hydro Tasmania Consulting), Geoscience Australia, Bureau of Meteorology, CSIRO, Tasmanian Partnership for Advanced Computing, Tasmanian Institute of Agricultural Research and the University of Tasmania.

The generation of the Climate Futures for Tasmania climate simulations was commissioned by the Antarctic Climate & Ecosystems Cooperative Research Centre (ACE CRC), as part of its Climate Futures for Tasmania project. The climate simulations are freely available through the Tasmanian Partnership for Advanced Computing digital library at www.tpac.org.au.

The intellectual property rights in the climate simulations belong to the Antarctic Climate & Ecosystems Cooperative Research Centre. The Antarctic Climate & Ecosystems Cooperative Research Centre grants to every person a permanent, irrevocable, free, Australia wide, non-exclusive licence (including a right of sub-licence) to use, reproduce, adapt and exploit the Intellectual Property Rights of the simulations for any purpose, including a commercial purpose.

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

9. Disclaimer

The material in this report is derived from climate change scenarios and projections by the Antarctic Climate & Ecosystems Cooperative Research Centre that are based on computer modelling. Modelling involves simplification of real physical processes that are not fully understood and which must be anticipated.

The Antarctic Climate & Ecosystems Cooperative Research Centre undertakes no duty to or accepts any responsibility to any party who may rely upon this document.

While every effort has been made to ensure that data is accurate, the information is provided without warranty of any kind whatsoever including any warranties as to the accuracy of the data or its performance or fitness for a particular use or purpose whatsoever.

The user of this information accepts any and all risks of such use, whether direct or indirect, and in no event shall the Antarctic Climate & Ecosystems Cooperative Research Centre be liable for any damages and/or costs, including but not limited to incidental or consequential damages of any kind, including economic damage or loss or injury to person or property, regardless of whether the Antarctic Climate & Ecosystems Cooperative Research Centre shall be advised, have reason to know, or in fact shall know of the possibility.

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

10. References

Allison I, Bindoff NL, Bindschadler RA, Cox PM, de Noblet N, England MH, Francis JE, Gruber N, Haywood AM, 1515 Karoly DJ, Kaser G, Le Quéré C, Lenton TM, Mann ME, McNeil BI, Pitman AJ, Rahmstorf S, Rignot E, 1516 Schellnhuber HJ, Schneider SH, Sherwood SC, Somerville RCJ, Steffen K, Steig EJ, Visbeck M and 1517 Weaver AJ 2009, The Copenhagen diagnosis, 2009: updating the world on the latest climate science, 1518 The University of New South Wales Climate Change Research Centre (CCRC), Sydney, Australia.

Barker, G., (2001) Parangana Dambreak Study Hydro Tasmania Consulting, Report Identification Number.: GEN-105470-CR-001

Corney, S., J.J. Katzfey, J.L. McGregor, M. Grose, J. Bennett, C.J. White, G. Holz and N.L. Bindoff, 2010. Climate Futures for Tasmania: climate modelling technical report, Antarctic Climate & Ecosystems Cooperative Research Centre, Hobart, Tasmania, in press, 2010.

DHI (Danish Hydraulic Institute), 2001. Modelling the World of Water. Available at http://www.dhisoftware.com.

Department of Environment and Resource Management (2009) Draft State Planning Policy Coastal Protection. The Queensland Government, Brisbane, Queensland.

Engineers Australia, 1999: Australian Rainfall and Runoff – A Guide to Flood Estimation. Engineers Australia, Canberra.

Gamble, S. and McConachy, F., 1999. Application of the Focussed Rainfall Growth Estimation Technique in Tasmania. Proceedings of Water99 Joint Congress, pp. 691-696, Brisbane, 6-8 July 1999. Inst. Engrs. Aust.

GHD, 1991, Huon River Flood Plain Study

Grose, M.R., I. Barnes-Keoghan, S.P. Corney, C.J. White, G.K. Holz, J.C. Bennett, S.M. Gaynor and N.L. Bindoff, 2010, Climate Futures for Tasmania: general climate technical report, Antarctic Climate & Ecosystems Cooperative Research Centre, Hobart, Tasmania, in press, 2010.

IPCC (Intergovernmental Panel on Climate Change), 2007. Summary for Policy Makers. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change [Parry, M.L., O.F., Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, (eds.)]. Cambridge University Press, Cambridge, UK, and New York, pp 7-22. Available at http://www.ipcc.ch.

Jones, D.A., W. Wang and R. Fawcett, 2009. High-quality spatial climate data-sets for Australia. Australian 1624 Meteorological and Oceanographic Journal, 58: 233-248.

49 Climate Futures for Tasmania - Flood Inundation Mapping Revision No: 0 25 February 2011

Knight, J., (2007) Huon Flood Evacuation Plan Hydro Tasmania Consulting, Report Engagement Number.: E201709-Report-01

Li, S., Gerke, D., Herweynen, R., Morse, A., Sheedy, J., Wallis, M., and White, F., (1995) Meadowbank Dambreak Study Hydro Electric Commission, Report Engagement Number.: ENE-0076-CR-001

McKintosh, P., M. Pook, and J. McGregor. (2006), Study of Future and Current Climate: A Scenario for the Tasmanian Region. Report for Hydro Tasmania. 73pp.

Meehl, G.A., T.F. Stocker, W.D. Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A. Kitoh, R. nutti, J.M. Murphy, A. Noda, S.C.B. Raper, I.G. Watterson, A.J. Weaver and Z-C. Zhao, 2007. ‘Global Climate Projections’ in: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. S. Solomon, D. Qin, M. Manning et al Cambridge, United Kingdom, Cambridge University Press.

Nandakumar, N., Weinmann, P.E., Mein, R.G. and Nathan, R.J. 1997, Estimation of Extreme Rainfalls Using the CRC-FORGE Method (For Rainfall Durations 24 to 72 Hours), Report 97/4.

Pilgrim, DH, (1999) Runoff Routing Methods, Book V in Australian Rainfall and Runoff - A Guide to Flood Estimation, the Institution of Engineers, Australia, Barton, ACT, 1999.

Post DA, Chiew FHS, Teng J, Vaze J, Yang A, Mpelasoka F, Smith I, Katzfey J, Marston F, Marvanek S, Kirono D, Nguyen K, Kent D, Donojue R, Li L and McVicar T (2009) Production of climate scenarios for Tasmania. A report to the Australian Government from the CSIRO Tasmania Sustainable Yields Project, CSIRO Water for a Healthy Country Flagship, Australia.

Raupach, M.R., P.R. Briggs, V. Haverd, E.A. King, M. Paget and C.M. Trudinger, 2008. Australian Water Availability Project (AWAP), final report for Phase 3. CSIRO Marine and Atmospheric Research component. CSIRO Marine and Atmospheric Research, Canberra, Australia, 67 pp.

Smythe, C., 1995 Review of the Spillway Design Flood for Paloona Dam Hydro-Electric Commission Consulting Business Unit Water Resources Department Report No.: ENE-0004-30-01-CR-003

Smythe, C., 2001(a) Review of the Flood Hydrology for Parangana, Rowallan and Mackenzie Dams Hydro Tasmania Consulting, Report No.: GEN-0309-CR-003.

Victorian Coastal Council (2008), Victorian Coastal Strategy. Victorian Coastal Council, Melbourne, Victoria.

Nathan, RJ and Weinmann, E, (1999) Estimation of Large to Extreme Floods, Book VI in Australian Rainfall and Runoff - A Guide to Flood Estimation, the Institution of Engineers, Australia, Barton, ACT, 1999.

White, C.J., L.A. Sanabria, M. Grose, S.P. Corney, J.C. Bennett, G.K. Holz, K.L. McInnes, R.P. Cechet, S.M. Gaynor and N.L. Bindoff, 2010. Climate Futures for Tasmania: extreme events technical report, Antarctic Climate & Ecosystems Cooperative Research Centre, Hobart, Tasmania, in press, 2010.

50 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

White, C.J., S. Corney, M. Grose, J. Bennett, G. Holz, K. McInnes, L.A. Sanabria, R.P. Cechet and N.L. Bindoff, Modelling Extreme Events in a Changing Climate using Regional Dynamically-Downscaled Climate Projections, International Environmental Modelling and Software Society (iEMSs) 2010 International Congress on Environmental Modelling and Software, Fifth Biennial Meeting, 5-8th July 2010, Ottawa, Canada, in press, 2010b.

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Appendices

Climate Futures for Tasmania 25 February 2011

A Climate Futures for Tasmania Rainfall Surface Map

A.1 1 in 100 AEP Rainfall Event, 24 hour duration, 5% Confidence Interval

55 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

A.2 1 in 100 AEP Rainfall Event, 24 hour duration, Mean

56 Climate Futures for Tasmania 25 February 2011

A.3 1 in 100 AEP Rainfall Event, 24 hour duration, 95% Confidence Interval

57 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

B Flood Frequency Curves

10000

1000 ) s / 3 m (

e 100 g r a h c s i D

GEV L2 Observed Data

1 1.01 2 5 10 20 50 100 200 AEP(1:Y)

Figure B-1 Mersey River Catchment Flood Frequency Curve GEV Curve

10000

1000 ) s / 3 m (

e 100 g

r a h c s i D

GEV L2 Observed Data

1 1.01 2 5 10 20 50 100 200 AEP(1:Y)

Figure B-2 Forth River Catchment Flood Frequency Curve GEV Curve

58 Climate Futures for Tasmania 25 February 2011

10000

1000 ) s / 3 m (

e 100 g

r a h c s i D

GEV L2 Observed Data

1 1.01 2 5 10 20 50 100 200 AEP(1:Y)

Figure B-4 Huon River Catchment Flood Frequency Curve GEV Curve

10000

1000 ) s / 3 m (

e 100 g

r a h c s i D

GEV L2 Observed Data

1 1.01 2 5 10 20 50 100 200 AEP(1:Y)

Figure B-3 Derwent River Catchment Flood Frequency Curve GEV Curve

59 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

C Hydrographs

C.1 Mersey River Catchment Hydrographs

Figure C-2 Mersey Hydrograph at Latrobe for the 1 in 10 AEP event

Figure C-3 Mersey Hydrograph at Latrobe for the 1 in 50 AEP event

60 Climate Futures for Tasmania 25 February 2011

Figure C-4 Mersey Hydrograph at Latrobe for the 1 in 100 AEP event

Figure C-5 Mersey Hydrograph at Latrobe for the 1 in 200 AEP event

61 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

C.2 Forth River Catchment Hydrographs

1:10 AEP 2070-2099 1:10 AEP 2040-2069 1:10 AEP 2010-2039 1:10 AEP 1961-1990

800

700

600

500 ) s / 3 m (

g 400 r a h c s i D 300

200

100

- 0.00 12.00 24.00 36.00 48.00 60.00 72.00 Duration (hr)

Figure C-1 Forth River Catchment Hydrograph at Wilmot for the 1 in 10 AEP event

1:50 AEP 2070-2099 1:50 AEP 2040-2069 1:50 AEP 2010-2039 1:50 AEP 1961-1990

1,200

1,000

800 ) s / 3 m (

g 600 r a h c s i D

400

200

- 0 12 24 36 48 60 72 Duration (hrs) Figure C-2 Forth River Catchment Hydrograph at Wilmot for the 1 in 50 AEP event

62 Climate Futures for Tasmania 25 February 2011

1:100 AEP 2070-2099 1:100 AEP 2040-2069 1:100 AEP 2010-2039 1:100 AEP 1961-1990

1,600

1,400

1,200

1,000 ) s / 3 m (

g 800 r a h c s i D 600

400

200

- 0 12 24 36 48 60 72 Duration (hrs) Figure C-3 Forth River Catchment Hydrograph at Wilmot for the 1 in 100 AEP event

1:200 AEP 2070-2099 1:200 AEP 2040-2069 1:200 AEP 2010-2039 1:200 AEP 1961-1990

1,800

1,600

1,400

1,200 ) s / 3

m 1,000 (

e g r a h

c 800 s i D

600

400

200

- 0 12 24 36 48 60 72 Duration (hrs)

Figure C-4 Forth River Catchment Hydrograph at Wilmot for the 1 in 200 AEP event

63 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

C.3 Derwent River Catchment Hydrographs

1-200 AEP 1961-1990 1-100 AEP 1961-1990 1-50 AEP 1961-1990 1-10 AEP 1961-1990

4,000

3,500

3,000 ) s / 3 2,500 m (

g 2,000 r a h

c 1,500 s i D 1,000

500

- 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 1 2 3 4 6 7 8 9 0 2 3 4 5 6 8 9 0 1 1 1 1 1 1 1 1 1 2 2 Duration (hrs) Figure C-5 Derwent River Catchment Hydrograph at Macquarie Plains for 1961-1990.

C.4 Huon River Catchment Hydrographs

2070-2099 2040-2069 2010-2039 1961-1990

3500

3000

2500

2000

1500

1000

500

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : : : 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 1 2 3 4 6 7 8 9 0 2 3 4 5 6 8 9 0 1 2 1 1 1 1 1 1 1 1 2 2 2 Figure C-6 Huon Hydrograph at Latrobe for the 1 in 10 AEP event

64 Climate Futures for Tasmania 25 February 2011

2070-2099 2040-2069 2010-2039 1961-1990

4000

3500

3000

2500

2000

1500

1000

500

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : : : 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 1 2 3 4 6 7 8 9 0 2 3 4 5 6 8 9 0 1 2 1 1 1 1 1 1 1 1 2 2 2 Figure C-7 Huon Hydrograph at Latrobe for the 1 in 50 AEP event

2070-2099 2040-2069 2010-2039 1961-1990

4500

4000

3500

3000

2500

2000

1500

1000

500

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : : : 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 1 2 3 4 6 7 8 9 0 2 3 4 5 6 8 9 0 1 2 1 1 1 1 1 1 1 1 2 2 2 Figure C-8 Huon Hydrograph at Latrobe for the 1 in 100 AEP event

65 Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

2070-2099 2040-2069 2010-2039 1961-1990

4500

4000

3500

3000

2500

2000

1500

1000

500

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : : : 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 1 2 3 4 6 7 8 9 0 2 3 4 5 6 8 9 0 1 2 1 1 1 1 1 1 1 1 2 2 2 Figure C-9 Huon Hydrograph at Latrobe for the 1 in 200 AEP event

66 Climate Futures for Tasmania 25 February 2011

D Flood Maps

D.1 Mersey River Catchment Flood Inundation Maps

Figure D-9 Mersey River Catchment Flood Map for the 1 in 10 AEP event Figure D-10 Mersey River Catchment Flood Map for the 1 in 50 AEP event Figure D-11 Mersey River Catchment Flood Map for the 1 in 100 AEP event Figure D-12 Mersey River Catchment Flood Map for the 1 in 200 AEP event

D.2 Forth River Catchment Flood Inundation Maps

Figure D-1 Forth River Catchment Flood Map for the 1 in 10 AEP event Figure D-2 Forth River Catchment Flood Map for the 1 in 50 AEP event Figure D-3 Forth River Catchment Flood Map for the 1 in 100 AEP event Figure D-4 Forth River Catchment Flood Map for the 1 in 200 AEP event

D.3 Derwent River Catchment Flood Inundation Maps

Figure D-5 Derwent River Catchment Flood Map for the 1 in 10 AEP event Figure D-6 Derwent River Catchment Flood Map for the 1 in 50 AEP event Figure D-7 Derwent River Catchment Flood Map for the 1 in 100 AEP event Figure D-8 Derwent River Catchment Flood Map for the 1 in 200 AEP event

D.4 Huon River Catchment Flood Inundation Maps

Figure D-13 Huon River Catchment Flood Map for the 1 in 10 AEP event Figure D-14 Huon River Catchment Flood Map for the 1 in 50 AEP event Figure D-15 Huon River Catchment Flood Map for the 1 in 100 AEP event Figure D-16 Huon River Catchment Flood Map for the 1 in 200 AEP event

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

E Mike11 Hydraulic Model Results

E.1 Mersey River Catchment

Table E1 Mersey River Catchment 1 in 10 AEP Peak Flood Level (m AHD) Peak Flood Level (m AHD) Chainage (m) 2010 - 2039 2040 - 2069 2070 - 2099

90 0.2 0.5 0.6

140 0.2 0.4 0.5

1030 0.3 0.6 0.8

2190 0.2 0.5 0.8

4930 0.1 0.3 0.5

4990 0.0 0.0 0.0

6290 0.2 0.4 0.6

7350 0.2 0.4 0.6

7890 0.0 0.0 0.0

9050 0.3 0.5 0.7

10990 0.3 0.5 0.8

11120 0.0 -0.1 -0.1

12210 0.0 0.0 0.0

12500 0.0 0.0 0.0

12540 0.0 0.0 0.0

13180 0.2 0.4 0.7

14430 0.3 0.5 0.7

15710 0.2 0.3 0.5

16620 0.2 0.4 0.6

17730 0.3 0.5 0.7

21760 0.3 0.4 0.5

23790 0.2 0.3 0.4

26060 0.3 0.7 0.9

30560 0.1 0.2 0.3

36310 0.2 0.3 0.5

38730 0.2 0.4 0.6

40920 0.2 0.4 0.5

42140 0.3 0.6 0.8

44040 0.3 0.6 0.8

47650 0.3 0.5 0.8

50820 0.2 0.5 0.7

Climate Futures for Tasmania 25 February 2011

Table E2 Mersey River Catchment 1 in 54800 0.1 0.3 0.5 50 AEP Peak Flood Level (m AHD)

57970 0.3 0.6 1.0

61500 0.2 0.5 0.7

65810 0.3 0.6 0.9

66550 0.4 0.7 1.1

66600 0.4 0.7 1.1

70290 0.5 0.9 1.3

75610 0.7 1.5 2.0

80300 0.4 0.8 1.2

80350 0.4 0.8 1.2

87020 0.6 1.1 1.5

87660 0.6 1.0 1.5

89180 0.2 0.5 0.6

89300 0.3 0.5 0.6

89530 0.2 0.3 0.4

90280 0.1 0.1 0.2

90580 0.1 0.1 0.1

90910 0.1 0.1 0.1

91640 0.1 0.2 0.3

91880 0.1 0.2 0.3

92250 0.3 0.4 0.5

92500 0.1 0.3 0.4

92550 0.1 0.2 0.4

92570 0.2 0.3 0.5

92830 0.1 0.2 0.3

93010 0.2 0.2 0.3

93380 0.2 0.3 0.3

93690 0.5 0.6 0.7

94050 0.6 0.7 0.8 94850 0.7 0.8 0.8 95940 0.6 0.7 0.7 97100 0.7 0.7 0.8 98290 0.8 0.8 0.8 99900 0.8 0.7 0.8 101000 0.8 0.8 0.8 101775 0.8 0.8 0.8 Mersey AEP Flood 1 in 50

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Peak Flood Level (m AHD) Chainage (m) 2010 - 2039 2040 - 2069 2070 - 2099

90 0.3 0.6 1.0

140 0.3 0.7 1.1

1030 0.5 0.8 1.2

2190 0.5 1.0 1.4

4930 0.4 0.8 1.1

4990 0.0 0.0 0.0

6290 0.4 0.7 1.1

7350 0.4 0.7 1.0

7890 0.0 0.0 0.0

9050 0.3 0.7 1.1

10990 0.4 0.8 1.2

11120 0.0 -0.1 0.0

12210 0.0 0.0 0.0

12500 0.0 0.0 0.0

12540 0.0 0.0 0.0

13180 0.3 0.7 1.1

14430 0.4 0.8 1.1

15710 0.4 0.7 1.0

16620 0.3 0.7 1.0

17730 0.3 0.7 0.9

21760 0.2 0.4 0.6

23790 0.3 0.5 0.7

26060 0.3 0.7 1.0

30560 0.2 0.5 0.7

36310 0.3 0.6 0.9

38730 0.4 0.8 1.2

40920 0.3 0.7 1.0

42140 0.5 0.9 1.4

44040 0.5 0.9 1.3

47650 0.4 0.8 1.2

50820 0.2 0.5 0.7

54800 0.3 0.6 0.9

57970 0.4 0.9 1.3

61500 0.3 0.6 1.0

65810 0.6 1.1 1.7

Climate Futures for Tasmania 25 February 2011

Mersey AEP Flood 1 in 50 Peak Flood Level (m AHD) Chainage (m) 2010 - 2039 2040 - 2069 2070 - 2099

66550 0.6 1.2 1.9

66600 0.6 1.2 1.8

70290 0.6 1.3 1.9

75610 0.6 1.3 1.9

80300 0.6 1.3 1.8

80350 0.6 1.3 1.8

87020 0.5 0.9 1.4

87660 0.4 0.8 1.2

89180 0.2 0.3 0.5

89300 0.1 0.2 0.4

89530 0.1 0.1 0.1

90280 0.0 0.0 0.1

90580 0.1 0.1 0.1

90910 0.0 0.1 0.2

91640 0.1 0.2 0.3

91880 0.2 0.3 0.4

92250 0.2 0.3 0.5

92500 0.1 0.3 0.4

92550 0.1 0.3 0.4

92570 0.2 0.3 0.5

92830 0.1 0.2 0.3

93010 0.1 0.2 0.3

93380 0.2 0.3 0.5

93690 0.4 0.5 0.6

94050 0.5 0.6 0.7 94850 0.5 0.6 0.7 95940 0.5 0.6 0.7 97100 0.6 0.6 0.7 98290 0.7 0.7 0.7 99900 0.8 0.8 0.8 101000 0.8 0.8 0.8 101775 0.8 0.8 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Table E3 Mersey River Catchment 1 in 100 AEP Peak Flood Level (m AHD) Mersey AEP Flood 1 in 100 Peak Flood Level (m AHD) Chainage (m) 2010 - 2039 2040 - 2069 2070 - 2099

90 0.4 0.7 1.0

140 0.4 0.8 1.1

1030 0.4 0.8 1.1

2190 0.5 0.9 1.3

4930 0.3 0.6 0.9

4990 0.0 0.0 0.0

6290 0.4 0.7 1.1

7350 0.4 0.7 1.0

7890 0.0 0.0 0.0

9050 0.4 0.8 1.2

10990 0.5 0.9 1.2

11120 0.0 -0.1 -0.1

12210 0.0 0.0 0.0

12500 0.0 0.0 0.0

12540 0.0 0.0 0.0

13180 0.4 0.8 1.1

14430 0.4 0.8 1.2

15710 0.3 0.6 0.9

16620 0.3 0.6 0.9

17730 0.3 0.6 0.9

21760 0.2 0.4 0.6

23790 0.3 0.6 0.8

26060 0.3 0.6 0.9

30560 0.2 0.4 0.5

36310 0.3 0.6 0.8

38730 0.5 0.9 1.3

40920 0.3 0.7 1.0

42140 0.5 1.0 1.4

44040 0.5 0.9 1.3

47650 0.4 0.8 1.2

50820 0.3 0.6 0.9

54800 0.3 0.6 0.8

57970 0.5 0.8 1.1

Climate Futures for Tasmania 25 February 2011

Mersey AEP Flood 1 in 100 Peak Flood Level (m AHD) Chainage (m) 2010 - 2039 2040 - 2069 2070 - 2099

61500 0.4 0.9 1.3

65810 0.7 1.2 1.7

66550 0.7 1.4 1.9

66600 0.7 1.3 1.8

70290 0.7 1.4 2.1

75610 0.7 1.5 2.1

80300 0.6 1.3 1.9

80350 0.6 1.3 1.9

87020 0.5 1.0 1.5

87660 0.3 0.7 1.2

89180 0.1 0.3 0.5

89300 0.1 0.3 0.4

89530 0.1 0.1 0.2

90280 0.1 0.2 0.2

90580 0.1 0.1 0.2

90910 0.1 0.2 0.3

91640 0.1 0.2 0.4

91880 0.1 0.2 0.4

92250 0.1 0.3 0.5

92500 0.3 0.5 0.6

92550 0.4 0.6 0.8

92570 0.2 0.4 0.5

92830 0.1 0.2 0.4

93010 0.2 0.3 0.4

93380 0.3 0.5 0.7

93690 0.4 0.6 0.7

94050 0.4 0.5 0.7 94850 0.4 0.5 0.7 95940 0.4 0.6 0.7 97100 0.5 0.6 0.7 98290 0.7 0.7 0.8 99900 0.8 0.8 0.8 101000 0.8 0.8 0.8 101775 0.8 0.8 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Table E4 Mersey River Catchment 1 in 200 AEP Peak Flood Level (m AHD) Mersey AEP Flood 1 in 200 Peak Flood Level (m AHD) Chainage (m) 2010 - 2039 2040 - 2069 2070 - 2099

90 0.0 0.6 0.8

140 0.0 0.7 1.0

1030 0.0 0.6 0.9

2190 0.0 0.7 1.1

4930 0.0 0.6 0.8

4990 0.0 0.0 0.0

6290 0.0 0.6 0.9

7350 0.0 0.6 0.9

7890 0.0 0.0 0.0

9050 0.0 0.5 0.7

10990 0.0 0.5 0.8

11120 -0.1 0.0 0.0

12210 0.0 0.0 0.0

12500 0.0 0.0 0.0

12540 0.0 0.0 0.0

13180 0.0 0.7 1.0

14430 0.0 0.7 1.0

15710 0.0 0.6 0.9

16620 0.0 0.6 0.9

17730 0.0 0.6 0.8

21760 0.1 0.4 0.5

23790 0.0 0.3 0.5

26060 0.0 0.5 0.7

30560 0.0 0.3 0.5

36310 0.0 0.5 0.7

38730 0.0 0.7 1.1

40920 0.0 0.6 0.9

42140 0.0 0.9 1.3

44040 0.0 0.8 1.2

47650 0.0 0.7 1.0

50820 0.0 0.5 0.7

54800 0.0 0.6 0.8

57970 0.0 0.6 1.0

Climate Futures for Tasmania 25 February 2011

Mersey AEP Flood 1 in 200 Peak Flood Level (m AHD) Chainage (m) 2010 - 2039 2040 - 2069 2070 - 2099

61500 0.0 0.6 1.0

65810 0.0 1.0 1.5

66550 0.0 1.1 1.6

66600 0.0 1.1 1.6

70290 0.0 1.2 1.8

75610 0.0 1.2 1.8

80300 0.0 1.2 1.7

80350 0.0 1.2 1.7

87020 0.2 1.0 1.5

87660 0.3 1.0 1.4

89180 0.1 0.4 0.6

89300 0.1 0.4 0.5

89530 0.1 0.2 0.3

90280 0.0 0.2 0.3

90580 0.0 0.2 0.3

90910 0.1 0.3 0.4

91640 0.1 0.3 0.4

91880 0.1 0.3 0.5

92250 0.0 0.2 0.3

92500 0.2 0.4 0.5

92550 0.2 0.3 0.4

92570 0.1 0.3 0.4

92830 0.1 0.3 0.4

93010 0.2 0.4 0.6

93380 0.3 0.6 0.8

93690 0.3 0.6 0.9

94050 0.3 0.6 0.8 94850 0.4 0.7 0.9 95940 0.4 0.7 0.8 97100 0.5 0.7 0.9 98290 0.7 0.8 0.9 99900 0.8 0.9 0.9 101000 0.8 0.8 0.8 101775 0.8 0.8 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

E.2 Forth River Catchment

Table E5 Forth River Catchment 1 in 10 AEP Peak Flood Level (m AHD) Forth AEP Flood 1 in 10 Peak Flood Level (m AHD) Chainage (m) 1961 - 1990 2010 - 2039 2040 - 2069 2070 - 2099

30870 0.7 1.0 1.4 0.7 31700 1.0 1.5 1.9 1.0 33320 0.8 1.2 1.6 0.8 35270 0.9 1.4 1.8 0.9 36100 0.9 1.4 1.8 0.9 38510 0.9 1.4 1.8 0.9 39230 1.0 1.5 1.9 1.0 40040 0.9 1.4 1.8 0.9 41970 0.9 1.3 1.7 0.9 43680 0.7 1.1 1.4 0.7 44580 0.7 1.0 1.2 0.7 45880 0.8 1.0 1.1 0.8 46880 0.8 0.9 1.0 0.8 47200 0.8 0.8 0.8 0.8 48200 0.8 0.8 0.8 0.8

Climate Futures for Tasmania 25 February 2011

Table E6 Forth River Catchment 1 in 50 AEP Peak Flood Level (m AHD) Forth AEP Flood 1 in 50 Peak Flood Level (m AHD) Chainage (m) 1961 - 1990 2010 - 2039 2040 - 2069 2070 - 2099

30870 0.5 0.9 1.4 0.5 31700 0.5 1.0 1.6 0.5 33320 0.5 1.0 1.5 0.5 35270 0.5 1.1 1.6 0.5 36100 0.5 1.0 1.6 0.5 38510 0.5 1.0 1.5 0.5 39230 0.6 1.1 1.6 0.6 40040 0.6 1.1 1.6 0.6 41970 0.5 1.0 1.4 0.5 43680 0.5 0.9 1.3 0.5 44580 0.4 0.7 1.0 0.4 45880 0.7 0.9 1.1 0.7 46880 0.7 0.9 1.0 0.7 47200 0.8 0.8 0.8 0.8 48200 0.8 0.8 0.8 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Table E7 Forth River Catchment 1 in 100 AEP Peak Flood Level (m AHD) Forth AEP Flood 1 in 100 Peak Flood Level (m AHD) Chainage (m) 1961 - 1990 2010 - 2039 2040 - 2069 2070 - 2099

30870 0.6 1.0 1.5 0.6

31700 0.6 1.1 1.6 0.6

33320 0.6 1.1 1.5 0.6

35270 0.6 1.2 1.7 0.6

36100 0.7 1.2 1.7 0.7

38510 0.6 1.0 1.5 0.6

39230 0.6 1.1 1.6 0.6

40040 0.7 1.2 1.7 0.7

41970 0.6 1.0 1.5 0.6

43680 0.6 1.0 1.5 0.6

44580 0.5 0.8 1.1 0.5

45880 0.7 0.9 1.1 0.7

46880 0.8 0.9 1.1 0.8

47200 0.8 0.8 0.8 0.8

48200 0.8 0.8 0.8 0.8

Climate Futures for Tasmania 25 February 2011

Table E8 Forth River Catchment 1 in 200 AEP Peak Flood Level (m AHD) Forth AEP Flood 1 in 200 Peak Flood Level (m AHD) Chainage (m) 1961 - 1990 2010 - 2039 2040 - 2069 2070 - 2099

30870 0.5 0.9 1.3 0.5

31700 0.6 1.1 1.6 0.6

33320 0.4 0.8 1.2 0.4

35270 0.6 1.1 1.5 0.6

36100 0.5 0.9 1.4 0.5

38510 0.5 1.0 1.4 0.5

39230 0.5 1.0 1.4 0.5

40040 0.5 1.0 1.4 0.5

41970 0.5 0.9 1.3 0.5

43680 0.5 0.9 1.4 0.5

44580 0.4 0.7 0.9 0.4

45880 0.6 0.8 1.0 0.6

46880 0.7 0.9 1.0 0.7

47200 0.8 0.8 0.9 0.8

48200 0.8 0.8 0.8 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

E.3 Derwent River Catchment

Table E9 Derwent River Catchment 1 in 10 AEP Peak Flood Level (m AHD) Change in Peak Flood Level from Baseline (m)

Chainage (m) Sea Level Rise of 0.8m

0 0.0 100 0.0 1600 0.0 2600 0.0 2839 0.0 3701 0.0 4562 0.0 5424 0.0 6285 0.0 8281 0.0 9863 0.0 10983 0.0 11800 0.0 12617 0.0 13434 0.0 14251 0.0 15217 0.0 16183 0.0 17120 0.0 18058 0.0 18995 0.0 19821 0.0 20648 0.0 21474 0.0 22301 0.0 23127 0.0 25100 0.0 25764 0.0 26278 0.0 26951 0.0 27623 0.0

Climate Futures for Tasmania 25 February 2011

Change in Peak Flood Level from Baseline (m)

Chainage (m) Sea Level Rise of 0.8m

28296 0.0 30108 0.0 31013 0.0 31919 0.0 32851 0.0 35646 0.0 36578 0.0 37512 0.0 38445 0.0 39379 0.0 41246 0.0 42225 0.0 43204 0.0 45162 0.1 45632 0.0 46099 0.1 46625 0.1 47196 0.1 47998 0.2 48395 0.2 48600 0.3 48910 0.3 49231 0.3 49549 0.3 49902 0.3 50259 0.4 50498 0.4 51101 0.4 51738 0.5 52479 0.6 53100 0.6 55907 0.6 58289 0.7

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Change in Peak Flood Level from Baseline (m)

Chainage (m) Sea Level Rise of 0.8m

61172 0.8 63153 0.8 64412 0.8 65555 0.7 66124 0.8 66527 0.8 67494 0.8

Climate Futures for Tasmania 25 February 2011

Table E10 Derwent River Catchment 1 in 50 AEP Peak Flood Level (m AHD) Change in Peak Flood Level from Baseline (m) Chainage (m) Sea Level Rise (0.8m)

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Change in Peak Flood Level from Baseline (m) Chainage (m) Sea Level Rise (0.8m)

30108 0.0 31013 0.0 31919 0.0 32851 0.0 35646 0.0 36578 0.0 37512 0.0 38445 0.0 39379 0.0 41246 0.0 42225 0.1 43204 0.1 45162 0.0 45632 0.1 46099 0.0 46625 0.1 47196 0.0 47998 0.1 48395 0.1 48600 0.1 48910 0.2 49231 0.1 49549 0.1 49902 0.2 50259 0.1 50498 0.2 51101 0.3 51738 0.3 52479 0.4 53100 0.3 55907 0.5 58289 0.6 61172 0.6

Climate Futures for Tasmania 25 February 2011

Change in Peak Flood Level from Baseline (m) Chainage (m) Sea Level Rise (0.8m)

63153 0.7 64412 0.6 65555 0.7 66124 0.8 66527 0.7 67494 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Table E11 Derwent River Catchment 1 in 100 AEP Peak Flood Level (m AHD) Change in Peak Flood Level from Baseline (m) Chainage (m) Sea Level Rise (0.8m)

0 0.0

100 0.0

1600 0.0

2600 0.0

2839 0.0

3701 0.0

4562 0.0

5424 0.0

6285 0.0

8281 0.0

9863 0.0

10983 0.0

11800 0.0

12617 0.0

13434 0.0

14251 0.0

15217 0.0

16183 0.0

17120 0.0

18058 0.0

18995 0.0

19821 0.0

20648 0.0

21474 0.0

22301 0.0

23127 0.0

25100 0.0

25764 0.0

26278 0.0

26951 0.0

27623 0.0

28296 0.0

30108 0.0

31013 0.0

Climate Futures for Tasmania 25 February 2011

31919 0.0

32851 0.0

35646 0.0

36578 0.0

37512 0.0

38445 0.0

39379 0.0

41246 0.0

42225 0.0

43204 0.1

45162 0.0

45632 0.0

46099 0.0

46625 0.0

47196 0.0

47998 0.1

48395 0.1

48600 0.1

48910 0.1

49231 0.1

49549 0.1

49902 0.1

50259 0.1

50498 0.1

51101 0.2

51738 0.2

52479 0.2

53100 0.3

55907 0.3

58289 0.5

61172 0.5

63153 0.6

64412 0.6

65555 0.7

66124 0.7

66527 0.8

67494 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Table E12 Derwent River Catchment 1 in 200 AEP Peak Flood Level (m AHD) Change in Peak Flood Level from Baseline (m) Chainage (m) Sea Level Rise (0.8m)

0 0.0

100 0.0

1600 0.0

2600 0.0

2839 0.0

3701 0.0

4562 0.0

5424 0.0

6285 0.0

8281 0.0

9863 0.0

10983 0.0

11800 0.0

12617 0.0

13434 0.0

14251 0.0

15217 0.0

16183 0.0

17120 0.0

18058 0.0

18995 0.0

19821 0.0

20648 0.0

21474 0.0

22301 0.0

23127 0.0

25100 0.0

25764 0.0

26278 0.0

26951 0.0

27623 0.0

28296 0.0

30108 0.0

31013 0.0

Climate Futures for Tasmania 25 February 2011

31919 0.0

32851 0.0

35646 0.0

36578 0.0

37512 0.0

38445 0.0

39379 0.0

41246 0.0

42225 0.1

43204 0.0

45162 0.0

45632 0.0

46099 0.1

46625 0.0

47196 0.0

47998 0.0

48395 0.0

48600 0.0

48910 0.1

49231 0.1

49549 0.1

49902 0.1

50259 0.0

50498 0.1

51101 0.2

51738 0.2

52479 0.2

53100 0.2

55907 0.3

58289 0.4

61172 0.5

63153 0.6

64412 0.6

65555 0.6

66124 0.7

66527 0.7

67494 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

E.4 Huon River Catchment

Table E13 Huon River Catchment 1 in 10 AEP Peak Flood Level (m AHD) Change in Peak Flood Level from Baseline (m) Chainage (m) 2010-2039 2040-2069 2070-2099

81318 0.7 1.5 2.3 82613 0.7 1.7 2.6 84713 0.7 1.6 2.5 87371 0.7 1.6 2.6 90869 0.8 1.7 2.5 95851 0.7 1.4 2.1 96946 0.7 1.4 2.1 96946 0.7 1.4 2.1 100333 0.6 1.2 1.8 102101 0.5 1 1.6 103151 0.5 1 1.5 104204 0.5 1 1.5 106250 0.5 0.9 1.4 107899 0.6 1 1.5 110993 0.7 1 1.3 114168 0.7 1 1.3 116054 0.6 0.9 1.2 116054 0.6 0.9 1.2 120546 0.7 0.9 1.1 129211 0.8 0.8 0.8 135659 0.8 0.8 0.9 142830 0.8 0.8 0.8 150000 0.8 0.8 0.8

Climate Futures for Tasmania 25 February 2011

Table E14 Huon River Catchment 1 in 50 AEP Peak Flood Level (m AHD) Change in Peak Flood Level from Baseline (m) Chainage (m) 2010-2039 2040-2069 2070-2099

81318 0.7 1.4 2.1 82613 0.8 1.6 2.4 84713 0.7 1.5 2.3 87371 0.8 1.6 2.4 90869 0.8 1.5 2.4 95851 0.6 1.2 1.9 96946 0.6 1.2 1.9 96946 0.6 1.2 1.9 100333 0.5 1.1 1.7 102101 0.5 0.9 1.4 103151 0.5 0.9 1.4 104204 0.5 0.9 1.4 106250 0.5 0.8 1.3 107899 0.5 0.9 1.3 110993 0.6 0.9 1.2 114168 0.6 0.8 1.2 116054 0.6 0.9 1.2 116054 0.6 0.9 1.2 120546 0.6 0.8 1.1 129211 0.8 0.8 0.9 135659 0.7 0.8 0.8 142829.5 0.8 0.8 0.8 150000 0.8 0.8 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

Table E15 Huon River Catchment 1 in 100 AEP Peak Flood Level (m AHD) Change in Peak Flood Level from Baseline (m) Chainage (m) 2010-2039 2040-2069 2070-2099

81318 0.8 1.4 2 82613 1 1.6 2.3 84713 0.9 1.6 2.3 87371 0.9 1.7 2.4 90869 0.8 1.5 2.2 95851 0.7 1.3 1.9 96946 0.7 1.2 1.8 96946 0.7 1.2 1.8 100333 0.6 1.1 1.6 102101 0.6 1 1.4 103151 0.5 0.9 1.3 104204 0.6 1 1.4 106250 0.5 0.9 1.3 107899 0.6 0.9 1.3 110993 0.6 0.9 1.2 114168 0.7 0.9 1.2 116054 0.6 0.9 1.2 116054 0.6 0.9 1.2 120546 0.7 0.9 1.1 129211 0.8 0.8 0.9 135659 0.8 0.8 0.8 142829.5 0.8 0.8 0.8 150000 0.8 0.8 0.8

Climate Futures for Tasmania 25 February 2011

Table E16 Huon River Catchment 1 in 200 AEP Peak Flood Level (m AHD) Change in Peak Flood Level from Baseline (m) Chainage (m) 2010-2039 2040-2069 2070-2099

81318 1 1.5 2 82613 1.1 1.8 2.3 84713 1 1.7 2.3 87371 1.1 1.8 2.4 90869 1 1.6 2.2 95851 0.9 1.4 1.9 96946 0.8 1.3 1.8 96946 0.8 1.3 1.8 100333 0.7 1.2 1.6 102101 0.7 1.1 1.4 103151 0.6 1 1.3 104204 0.7 1 1.4 106250 0.6 1 1.3 107899 0.7 1 1.3 110993 0.7 0.9 1.2 114168 0.7 1 1.2 116054 0.7 0.9 1.2 116054 0.7 0.9 1.2 120546 0.7 0.9 1.1 129211 0.8 0.9 0.9 135659 0.8 0.8 0.8 142829.5 0.8 0.8 0.8 150000 0.8 0.8 0.8

Climate Futures for Tasmania - Flood Inundation Mapping 25 February 2011

The information contained in this document has been carefully compiled but Entura takes no responsibility for any loss or liability of any kind suffered by any party, not being the intended recipient of this document, in reliance upon its contents whether arising from any error or inaccuracy in the information or any default, negligence or lack of care in relation to the preparation of the information in this document.