Port Adelaide Seawater Stormwater Flooding Study
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City of Port Adelaide Enfield O C E A N I C S A U S T R A L I A Volume 1 – Final Report Port Adelaide Seawater Stormwater Flooding Study Principal Contacts Drew Jacobi (Tonkin Consulting) Bill Syme (WBM Oceanics Australia) October 2005 Ref No 20020477RA3D O C E A N I C S A U S T R A L I A Table of Contents Table of Contents City of Port Adelaide Enfield Port Adelaide Seawater Stormwater Flooding Study Final Report VOLUME 1 – FINAL REPORT 1. Introduction 1 2. Land Subsidence 2 2.1 Background 2 2.2 Causes of Land Subsidence 3 2.3 Measurement of Land Subsidence 4 2.3.1 E&WS Survey Mark Re-levelling 4 2.3.2 Deep Bench Mark Survey 6 2.4 Future Changes to Land Subsidence Rates 6 2.4.1 Changes in Groundwater Use 6 2.4.2 Land Reclamation 7 2.5 Recommendations 7 2.5.1 Adoption of Land Subsidence Rates for this Study 7 2.5.2 Further Work 8 3. Tide Analysis 9 3.1 Storm Tide Analysis Summary 9 3.1.1 Overview 9 3.1.2 Tide Datums 9 3.1.3 Storm Height and Duration Analysis 10 3.1.4 Storm Tide Hydrograph Synthesis 11 3.1.5 Summary of Highest 25 Events 12 3.1.6 Basic Equations 14 3.2 Relationship between storm surges and rainfall events 14 4. Seawater Inundation and Protection 17 4.1 Introduction 17 4.2 Seawater Hydraulic Modelling 18 4.2.1 Data Collation and Review 18 4.2.2 Digital Elevation Model (DEM) Development 18 4.2.3 Hydraulic Model 19 4.3 Seawater Model Calibration 20 4.3.1 Selection of Seawater Calibration Event 20 4.3.2 Calibration to 1999 Event 23 4.4 Preliminary Future Conditions Modelling 26 4.5 Damages Assessment 27 4.6 Structural Condition Assessment 31 4.7 Seawater Flood Protection 31 4.8 Concept Sea Defence Upgrade 31 4.8.1 Background 31 4.8.2 Design Requirements 32 4.8.3 Concept Design 32 4.8.4 Outer Harbour 34 4.8.5 Estimated Costs 34 City of Port Adelaide Enfield Port Adelaide Seawater Stormwater Flooding Study – Final Report 20020477RA3D.doc Revision: D Date: 10/10/05 Page: i O C E A N I C S A U S T R A L I A Table of Contents 5. Local Stormwater Inundation and Protection 36 5.1 Introduction 36 5.2 Seawater – Stormwater Interaction Methodology 36 5.3 TUFLOW Model 37 5.4 ILSAX Model 38 5.5 Design ‘Average’ Tide Cycle 39 5.6 100 year ARI Tide Cycle 39 5.7 Stormwater Drainage Performance Measurement 40 5.8 Stormwater Drainage Performance Requirements 40 5.9 Possible Future Increases to Rainfall Intensities and Impacts 41 5.9.1 Literature Review 41 5.9.2 Rainfall Intensity Changes Adopted for this Study 42 5.10 Anthony Street Catchment 42 5.10.1 Existing System 42 5.10.2 Proposed Upgrade Works 43 5.11 Centre Street and Jetty Road Catchments 43 5.11.1 Existing System 43 5.11.2 Proposed Upgrade Works 44 5.12 Hamilton Avenue Catchment 44 5.12.1 Existing System 44 5.12.2 Proposed Upgrade Works 44 5.13 Osborne Catchment 45 5.13.1 Existing System 45 5.13.2 Proposed Upgrade Works 45 5.14 Port Adelaide Centre Catchment 46 5.14.1 Existing System 46 5.14.2 Proposed Upgrade Works 46 5.15 Semaphore Road Catchment 47 5.15.1 Existing System 47 5.15.2 Proposed Upgrade Works 48 5.16 Future Sea Level / Land Subsidence Scenarios 48 5.17 Upgrade Costs 48 5.18 Recommended Future Scenario 49 5.19 Further Work 50 6. Wetlands and Ponding Basins Inundation and Protection 51 6.1 Methodology and Procedure for Wetlands and Ponding Basins Modelling 51 6.1.1 Background 51 6.1.2 Hydraulic Model Development 51 6.1.3 Digital Elevation Model Development 52 6.1.4 Boundary Conditions 52 6.2 Wetlands and Ponding Basins Existing Drainage Systems / Existing Development 52 6.2.1 Barker Inlet Wetlands Management Plan 52 6.2.2 Sea Level Rise / Land Subsidence Combinations 53 6.2.3 Design Wetland Standing Water Level 53 6.2.4 Concept Seawall Alignment 54 6.2.5 Storm Duration 54 6.2.6 Flooding Scenarios (Sensitivity Tests) 56 6.3 Peak Flood Levels 57 6.4 Further Work 59 7. Summary 60 8. References 62 City of Port Adelaide Enfield Port Adelaide Seawater Stormwater Flooding Study – Final Report 20020477RA3D.doc Revision: D Date: 10/10/05 Page: ii O C E A N I C S A U S T R A L I A Table of Contents Tables Table 2-1 Average Land Subsidence relative to Hope Valley Reservoir Bench Mark (Culver, 1970) 4 Table 2-2 Average Land Subsidence (1983-1994) relative to rock pin bench marks at the Tollgate 6 Table 2-3 Discharge from Upper Tertiary Aquifer 6 Table 3-1 Tide Datums 9 Table 3-2 25 Highest Tidal Events 12 Table 3-3 Correlation Between Top 25 Storm Tide and Storm Surge Events 13 Table 3-4 Calculation Variables 14 Table 4-1 Dataset Acquisition and Sources 18 Table 4-2 Land Uses Types 19 Table 4-3 Meteorological Events with 25 Highest Peak Tide Heights 20 Table 4-4 Future Conditions Scenarios of Sea Level Rise and Land Subsidence 26 Table 4-5 Predicted Outer and Inner Harbour Levels 27 Table 4-6 RAM Damages for Large Non Residential Buildings 27 Table 4-7 Building Elevation Adjustments 28 Table 4-8 Building Size Classification 28 Table 4-9 100 year ARI Flood Damage Estimates 29 Table 4-10 Sea Defence System Required Threshold Levels 32 Table 4-11 Concept Sea Defence Upgrade Cost Estimates 34 Table 5-1 100 year ARI tide levels at Stormwater Outfalls 39 Table 5-2 Local Stormwater Drainage Upgrade Cost Estimates 49 Table 6-1 Design Standing Water Levels 53 Table 6-2 Wetland and Ponding Basins Peak Flood Levels 57 Table 6-3 100 Year Ponding Basin Peak Flood Levels Comparison 57 Table 6-4 Maximum Allowable Pond Flood Levels 58 Figures Figure 2-1 Bench Mark Level Changes relative to Hope Valley (Culver, 1970) 5 Figure 3-1 Rainfall versus Tidal Anomaly – Outer Harbour 16 Figure 3-2 Rainfall versus Tidal Anomaly – Outer Harbour 16 Figure 4-1 June 1999 Seawater Calibration Event (Levels to mOHD) 22 Figure 4-2 Preliminary Model Calibration Results 24 Figure 4-3 Revised Model Calibration Results 25 Figure 4-4 Flood Damage Costs (Lower Case) 30 Figure 4-5 Flood Damage Costs (Upper Case) 30 Figure 4-6 Demountable Flood Defence System (Demflood System) 33 Figure 6-1 Magazine Creek Wetland Outlet 100 Year ARI Water Level Comparison 54 Figure 6-2 Range Wetland Outlet 100 Year ARI Water Level Comparison 55 Figure 6-3 Ponding Basin Outlet 100 Year ARI Water Level Comparison 55 Figure 6-4 Barker Inlet Wetland Outlet 100 Year ARI Water Level Comparison 56 Appendices Appendix A Historical Upper Tertiary (T1) Aquifer Potentiometric Surface Levels (Gerges, 1996) Appendix B Storm Tide Analysis Additional Information Appendix C Historical Storm Tide Meteorological Profiles VOLUME 2 – DRAWINGS City of Port Adelaide Enfield Port Adelaide Seawater Stormwater Flooding Study – Final Report 20020477RA3D.doc Revision: D Date: 10/10/05 Page: iii O C E A N I C S A U S T R A L I A Document History and Status Document History and Status Rev Description Author Rev’d App’d Date A Issued for review DJ/WJS KSS DJ 29/04/05 B Sec 3.2, 4.5 added DJ/WJS KSS DJ 18/05/05 C Final DJ/WJS KSS DJ 29/07/05 D Revised Ponding Basin Levels DJ/WJS KSS DJ 10/10/05 City of Port Adelaide Enfield Port Adelaide Seawater Stormwater Flooding Study – Final Report 20020477RA3D.doc Revision: D Date: 10/10/05 Page: iv O C E A N I C S A U S T R A L I A Introduction 1. Introduction The City of Port Adelaide Enfield together with project partners including the Coast Protection Board, Flinders Ports, Torrens Catchment Water Management Board, Land Management Corporation and Transport SA have commissioned this Study to evaluate seawater and stormwater flood risks in Port Adelaide. Funding for the Study has also been obtained from the Commonwealth Government under the Natural Disasters Risk Management Studies Program. The aim of the Flood Risk Management Study is to identify the risks and develop and implement a strategy to protect the vulnerable areas of the City from the risk of seawater and stormwater flooding taking into account the possible sea level rise and land subsidence over the next hundred years. This Study is intended to be conducted in three phases as follows: Phase 1: Risk Assessment/Preliminary Treatment – Analyse and evaluate risk of seawater and stormwater flooding and identify concept strategies. Phase 2: Risk Treatment Study – Develop detailed strategies, including design and development of management measures and development controls. Phase 3: Treatment Implementation – Implementation of control measures. This report examines Phase 1 of the Flood Risk Management Study. City of Port Adelaide Enfield Port Adelaide Seawater Stormwater Flooding Study – Final Report 20020477RA3D.doc Revision: D Date: 10/10/05 Page: 1 O C E A N I C S A U S T R A L I A Land Subsidence 2. Land Subsidence 2.1 Background Historically land subsidence has been identified as a factor to be taken into account in the analysis of tidal records.