Queensland Urban Drainage Manual 2016 Edition PDF

QUEENSLAND URBAN DRAINAGE MANUAL FOURTH EDITION Queensland Urban Drainage Manual Fourth edition, 2016 (Institute of Public Works Engineering Australasia, Queensland Division) Third edition, 2013 (Department of Energy and Water Supply) Second edition reprint, 2008 (CD-ROM integrating Volume 2) Second edition, 2007, Volume 1 only (Department of Natural Resources and Water) Second reprint, edition 1-2, 1994 First reprint, edition 1-1, 1993 First edition, 1992 (Department of Primary Industries) Published by: the Institute of Public Works Engineering Australasia, Queensland (IPWEAQ) © Copyright 2017 Institute of Public Works Engineering Australasia, Queensland. No part of this publication can be reproduced without the prior consent of the joint owners, the Department of Energy & Water Services (DEWS) and the Institute of Public Works Engineering Australasia, Queensland Division Ltd (IPWEAQ).Some diagrams are supplied by, and remain the intellectual property of, Catchments & Creeks Pty Ltd (refer to ‘Acknowledgments’). We acknowledge the contribution of the Brisbane City Council to the development of the publication and their continued involvement as a key stakeholder. Every effort and care has been taken by the authors and the sponsoring organisations to verify that the methods and recommendations contained in this Manual are appropriate for Queensland conditions. Notwithstanding these efforts, no warranty or guarantee, express, implied, or statutory is made as to the accuracy, reliability, suitability or results of the methods or recommendations. The authors and sponsoring organisations shall have no liability or responsibility to the user or any other person or entity with respect to any liability, loss or damage caused or alleged to be caused, directly or indirectly, by the adoption and use of the methods and recommendations of the Manual, including, but not limited to, any interruption of service, loss of business or anticipatory profits, or consequential damages resulting from the use of the Manual. Use of the Manual requires professional interpretation and judgement. Appropriate design procedures and assessment must be applied, to suit the particular circumstances under consideration. Published 2017 For more information, please contact Ross Guppy Director, Technical Products IPWEAQ [email protected] Queensland Urban Drainage Manual 2016 Edition ii Chapters 1 Introduction 2. Stormwater planning 3. Legal aspects 4. Catchment hydrology 5. Detention/retention systems 6. Computer models 7. Urban drainage 8. Stormwater outlets 9. Open channels 10. Waterway crossings 11. Environmental considerations 12. Safety aspects 13. Miscellaneous matters 14. References 15. Index Appendix 1 Pipe flow design charts Appendix 2 Structure pressure change coefficient charts Appendix 3 Road flow capacity charts Queensland Urban Drainage Manual 2016 Edition iii Contents Page Preface xiii Acknowledgments xv List of tables xvii List of figures xx 1 Introduction 1.1 Use of this manual 1-1 1.2 Background Notes 1-2 1.3 Consideration of regional factors 1-2 2 Stormwater planning 2.1 Purpose 2-1 2.2 General 2-1 2.3 Objectives and principles of stormwater management 2-2 2.4 Other related management philosophies 2-5 2.5 National Context 2-5 2.6 State context 2-6 2.6.1 State Planning Policy (state interests) 2-6 2.6.2 Healthy Waters Management Plans 2-7 2.6.3 Planning legislation 2-8 2.7 Local context 2.8 2.8 Urban stormwater drainage system planning 2.9 2.9 Climate change 2-10 3 Legal aspects 3.1 An introduction to the Australian legal system 3-1 3.2 QUDM and the law 3-1 3.3 Key legal concepts for stormwater design 3-2 3.4 Potential legal requirements for stormwater 3-3 3.5 Due diligence assessment 3-3 3.6 Stormwater changes – including nuisance 3-4 3.6.1 Diversion of stormwater 3-4 3.6.2 Concentration of stormwater flows 3-5 3.6.3 Changes in other flow characteristics 3-5 3.6.4 Adverse impacts on the future use or value of land 3-5 3.7 Common law 3-5 3.7.1 Surface water 3-6 3.7.2 Riparian rights 3-7 3.7.3 Regulatory authorities 3-7 3.8 Tenure for proposed drainage works 3-7 3.8.1 Non-freehold land 3-8 3.8.2 Freehold land 3-8 3.9 Lawful discharge of stormwater 3-8 3.9.1 Lawful point of discharge test 3-9 3.10 Discharge agreements issued by down-slope property owners 3-10 3.11 Drainage reserves 3-11 Queensland Urban Drainage Manual 2016 Edition iv 3.12 Registered Drainage easements 3-11 3.12.1 Easements generally 3-11 3.12.2 Need for registered easements in stormwater and drainage projects 3-12 3.12.3 Creation or acquisition of registered easements and existing easements 3-13 3.12.4 Drainage easement dimensions 3-14 3.13 Acquiring registered easement rights 3-14 3.13.1 Voluntary acquisition by private treaty 3-14 3.13.2 Compulsory acquisition by a local government 3-15 3.13.3 Imposition of statutory rights under the Property Law Act 3-16 3.14 Process for private developers seeking a registered drainage easement or drainage reserve over downstream property 3-16 3.15 Statutory approvals and other requirements 3-17 3.15.1 Design requirements for State-controlled transport corridors 3-20 4 Catchment hydrology 4.1 Introduction 4-1 4.2 Choice of hydrologic method 4-2 4.2.1 Rational Method 4-3 4.2.2 Utilisation of the Rational Method within complex catchments 4-4 4.2.3 Runoff-routing models 4-4 4.2.4 Regional flood frequency analysis 4-5 4.3 The Rational Method 4-6 4.4 Catchment area 4-6 4.5 Coefficient of discharge 4-7 4.6 Time of concentration (Rational Method) 4-9 4.6.1 General 4-9 4.6.2 Minimum time of concentration 4-9 4.6.3 Methodology of various urban catchments 4-10 4.6.4 Standard inlet time 4-11 4.6.5 Travel times from roof to main system connection 4-12 4.6.6 Overland flow travel times 4-13 4.6.7 Initial estimate of kerb, pipe and channel flow time 4-15 4.6.8 Kerb flow travel times 4-17 4.6.9 Pipe flow travel times 4-19 4.6.10 Open channel flow travel times 4-19 4.6.11 Time of concentration for rural and creek catchments 4-20 4.7 The partial area effect 4-22 4.8 Intensity-frequency-duration data 4-22 4.9 Estimation of runoff volume 4-23 4.9.1 General 4-23 4.9.2 Estimation of annual average runoff volume 4-23 4.9.3 Estimation of runoff volume from a single storm 4-23 5. Detention/retention systems 5.1 General 5-1 5.2 Master drainage planning 5-1 5.3 The uses of stormwater detention and retention 5-1 5.4 Limitations on the use of stormwater detention and retention 5-2 5.5 Design objectives and standards 5-2 5.5.1 General 5-2 Queensland Urban Drainage Manual 2016 Edition v 5.5.2 On-site detention systems 5-3 5.5.3 Discharge restrictions due to limited down-slope drainage capacity 5-3 5.5.4 Controlling local stormwater flooding 5-4 5.5.5 Controlling downstream creek flooding 5-4 5.5.6 Minimising the risk of accelerated channel erosion 5-5 5.5.7 Controlling stormwater runoff to reduce stress on aquatic life 5-6 5.5.8 Summary of overall detention/retention design objectives 5-6 5.6 Basin sizing and flood routing 5-7 5.6.1 Initial basin sizing 5-7 5.6.2 Final basin sizing 5-9 5.6.3 Temporal patterns 5-9 5.6.4 Allowance for existing channel storage 5-10 5.7 Basin freeboard 5-11 5.8 Basin floor drainage 5-11 5.9 Low-level basin outlet structures 5-12 5.9.1 Types of basin outlets 5-12 5.9.2 Orifice flow equation 5-12 5.9.3 Protection of basin outlet 5-13 5.9.4 Pipe protection 5-13 5.9.5 Outfall protection 5-14 5.10 High-level outlet structures 5-14 5.10.1 Extreme flood event 5-14 5.10.2 Spillway design 5-15 5.11 Embankments 5-15 5.12 Public safety issues 5-16 5.13 Statutory requirements 5-17 6. Computer models 6.1 Introduction 6-1 6.2 Computer models 6-1 6.2.1 Hydrologic models 6-1 6.2.2 Hydraulic models 6-1 6.2.3 Water quality models 6-2 6.3 Reporting of numerical model outcomes 6-2 7. Urban drainage 7.1 Planning issues 7-1 7.2 The major/minor drainage system 7-1 7.2.1 General 7-1 7.2.2 Minor drainage system 7-1 7.2.3 Major drainage system 7-2 7.2.4 Operation of the drainage system during severe storms 7-3 7.2.5 Preparation of Severe Storm Impact Statements 7-4 7.3 Design standards 7-4 7.3.1 Design AEPs 7-4 7.3.2 Selection of the major storm AEP based on risk assessment 7-6 7.3.3 Consideration of events in excess of the major storm 7-6 7.3.4 Land use/development categories 7-6 7.3.5 Essential community infrastructure 7-8 7.3.6 Overland flow paths 7-8 Queensland Urban Drainage Manual 2016 Edition vi 7.3.7 Cross drainage structures (culverts) 7-8 7.3.8 Flood evacuation routes 7-9 7.3.9 Basements and non-habitable rooms of buildings 7-9 7.3.10 Public car parks 7-10 7.3.11 Areas of manufacture or storage of bulk hazardous materials 7-10 7.3.12 Freeboard 7-10 7.3.13 Risk-based freeboard requirements 7-10 7.3.14 Easement widths 7-11 7.3.15 Minimum floor levels 7-11 7.3.16 Flow depth and width limitations 7-14 7.4 Roadway flow limits and capacity 7-17 7.4.1 Introduction 7-17 7.4.2 Minor and major storm conditions 7-17 7.4.3 General flow width, depth and velocity limits 7-18 7.4.4 Flow width limits for pedestrian safety 7-19 7.4.5 Flow width limits for traffic safety 7-20 7.4.6 General requirements 7-20 7.5 Stormwater inlets 7-23 7.5.1 Types of stormwater inlets 7-23 7.5.2 Provision for blockage 7-23 7.5.3 Kerb inlets in roads 7-24 7.5.4 Field inlets 7-27 7.5.5 Open pipe inlets 7-30 7.6 Access chambers 7-31 7.6.1 General 7-31 7.6.2 Spacing 7-31 7.6.3 Fluid mechanics within access chambers 7-31 7.6.4 Sizing access chambers 7-32 7.6.5 Access chamber tops 7-33 7.6.6 Deflection of pipe joints, splayed joints etc. 7-33 7.6.7 Reduction in pipe size 7-33 7.6.8 Surcharge chambers 7-33 7.7 Pipeline location 7-35 7.8 Pipe material and standards 7-36 7.8.1 Local authority requirements 7-36 7.8.2 Standards 7-36 7.8.3 Pipes and pipe laying 7-37 7.8.4 Box sections 7-38 7.8.5 Access chambers and structures 7-38 7.9 Structural design of pipelines 7-40 7.10 Minimum cover over pipes 7-41 7.11 Flow velocity limits 7-42 7.12 Pipe grade limits 7-43 7.13 Roof and allotment drainage 7-44 7.13.1 General 7-44 7.13.2 Roof drainage 7-44 7.13.3 Levels of roof and allotment drainage 7-44 7.13.4 Rear of allotment drainage systems 7-48 7.13.5 Effect of roof and allotment drainage on the primary drainage network 7-52 7.13.6 Managing the overland flow component of inter-allotment drainage 7-52 Queensland Urban Drainage Manual 2016 Edition vii 7.13.7 The use of easements in the management of inter-allotment drainage 7-52 7.13.8 Ownership of allotment and inter-allotment drainage structures 7-52 7.13.9 Inter-allotment drainage in rural residential areas 7-53 7.13.10 Level 0 drainage 7-53 7.13.11 Level I drainage 7-54 7.13.12 Level II drainage (rear of allotment drainage) 7-55 7.13.13 Level III drainage (rear of allotment drainage) 7-57 7.13.14 Level IV drainage 7-59 7.13.15 Level V drainage (rear of allotment drainage) 7-60 7.14 Public utilities and other services 7-61 7.14.1 General 7-61 7.14.2 Clearances to services 7-61 7.15 Discharge calculations 7-62 7.15.1 General 7-62 7.15.2 Design procedure 7-62 7.16 Hydraulic calculations 7-63 7.16.1 General 7-63 7.16.2 Pipe and structure losses 7-63 7.16.3 Hydraulic grade line and total energy line 7-64 7.16.4 Methods of design 7-65 7.16.5 Starting hydraulic grade level 7-65 7.16.6 Freeboard at inlets and junctions 7-66 7.16.7 Pipe capacity 7-68 7.16.8 Pressure changes at junction stations 7-68 7.16.9 Inlets and outlets 7-71 7.16.10 Bends 7-73 7.16.11 Obstructions or penetrations 7-75 7.16.12 Branch lines without a structure 7-75 7.16.13 Expansions and contractions (pipes flowing full) 7-76 7.16.14 Surcharge chambers 7-78 7.16.15 Hydraulic grade line (pipes flowing partially full) 7-81 7.16.16 Plotting of HGL on longitudinal section 7-82 7.16.17 Equivalent pipe determination 7-83 8. Stormwater outlets 8.1 Introduction 8-1 8.2 Factors affecting tailwater level 8-1 8.2.1 Contributing factors 8-1 8.2.2 Tidal variation 8-1 8.2.3 Storm surge 8-2 8.2.4 Wave setup 8-2 8.2.5 Climate change 8-2 8.3 Selection of tailwater level 8-3 8.3.1 Tailwater levels for tidal outfalls (oceans and bays) 8-3 8.3.2 Tailwater levels for tidal outfalls (rivers and creeks) 8-3 8.3.3 Tailwater levels for non-tidal outfalls 8-4 8.3.4 Coincident flooding 8-4 8.4 Design of tidal outlets 8-5 8.4.1 All tidal outlets 8-6 8.4.2 Open channel outlets (tidal) 8-6 Queensland Urban Drainage Manual 2016 Edition viii 8.4.3 Piped outlets (tidal) 8-7 8.4.4 Outlets to tidal estuaries and waterways 8-7 8.4.5 Outlets to beaches 8-7 8.4.6 Outlets subject to severe wave action 8-8 8.4.7 Outlets discharging through acid sulfate soils 8-8 8.5 Design of non-tidal outlets 8-9 8.5.1 General 8-9 8.5.2 Discharge to grass swales 8-12 8.5.3 Partial discharge via a surcharge chamber 8-13 8.5.4 Discharge to constructed outlet channels 8-13 8.5.5 Discharge to waterways 8-15 8.5.6 Discharge to lakes 8-16 8.6 Backflow control systems 8-17 8.7 Outlet energy dissipation 8-18 8.7.1 General 8-18 8.7.2 Rock pad outlet structures 8-19 9. Open channels 9.1 General 9-1 9.2 Planning issues 9-1 9.2.1 Legislative requirements 9-1 9.2.2 Retention of natural waterways 9-1 9.2.3 Rehabilitation of modified waterways 9-2 9.2.4 Selection of channel type 9-3 9.3 Open channel hydraulics 9-5 9.3.1 Hydraulic analysis 9-5 9.3.2 Design flow 9-5 9.3.3 Starting tailwater level 9-5 9.3.4 Channel freeboard 9-5 9.3.5 Use of Manning's equation 9-6 9.3.6 Energy losses at channel transitions and channel bends 9-10 9.4 Constructed channels with hard linings 9-12 9.4.1 Contraction and expansion joints 9-12 9.4.2 Step irons 9-12 9.4.3 Pressure relief weep holes 9-12 9.4.4 Treatment of channel inverts 9-12 9.4.5 Lateral protection and cut-off walls 9-12 9.4.6 Downstream scour protection 9-12 9.4.7 Rock mattress channels 9-12 9.5 Constructed channels with soft linings 9-13 9.5.1 Reducing flow velocities in channels with soft linings 9-13 9.5.2 Treatment of channel inverts 9-13 9.5.3 Recommended maximum average flow velocities 9-13 9.5.4 Recommended maximum channel side slopes 9-15 9.5.5 Tidal channels 9-15 9.6 Natural channel design 9-16 9.7 Design considerations for all channels 9-17 9.7.1 Safety issues 9-17 9.7.2 Access and maintenance berms 9-17 9.7.3 Fish passage 9-17 Queensland Urban Drainage Manual 2016 Edition ix 9.7.4 Terrestrial passage 9-18 9.7.5 Connectivity 9-18 9.7.6 Human movement corridors 9-18 9.7.7 Open channel drop structures 9-18 9.7.8 In-stream lakes and wetlands 9-19 9.7.9 Design and construction through acid sulfate soils 9-19 9.8 Low-flow channels 9-21 9.8.1 General 9-21 9.8.2 Design capacity of low-flow channels 9-21 9.8.3 Design considerations 9-21 9.8.4 Edge protection for low-flow channels 9-22 9.9 Use of rock in drainage channels 9-23 9.9.1 General 9-23 9.9.2 Rock sizing for the lining of drainage channels 9-24 9.9.3 Rock sizing for the lining of batter chutes 9-25 9.9.4 Rock sizing for the stabilisation of channel banks 9-26 9.9.5 Rock sizing for the design of constructed waterway riffles 9-26 9.9.6 Rock sizing for the stabilisation of waterway and gully chutes, and minor dam spillways 9-27 9.9.7 Rock sizing for the design of outlet structures 9-32 9.9.8 Rock sizing for the design of energy dissipaters 9-32 10. Waterway crossings 10.1 Bridge crossings 10-1 10.1.1 General 10-1 10.1.2 Blockage factors 10-1 10.1.3 Hydraulics of scupper pipe outflow channels 10-1 10.2 Causeway crossings 10-3 10.3 Ford crossings 10-4 10.4 Culvert crossings 10-4 10.4.1 Choice of design storm 10-4 10.4.2 Consideration of flows in excess of the nominated design storms 10-4 10.4.3 Location and alignment of culverts 10-5 10.4.4 Allowable afflux 10-6 10.4.5 Culvert sizing considerations 10-6 10.4.6 Preliminary sizing of culverts 10-6 10.4.7 Hydraulic analysis of culverts 10-7 10.4.8 Culvert elevation and gradient 10-7 10.4.9 Minimum cover 10.8 10.4.10 Blockage considerations and debris deflector walls 10-8 10.4.11 Sediment control issues 10-10 10.4.12 Roadway barriers 10-10 10.4.13 Terrestrial passage requirements 10-11 10.4.14 Fish passage requirements 10-11 10.4.15 Outlet scour control 10-11 10.4.16 Safety issues 10-11 Queensland Urban Drainage Manual 2016 Edition x 11. Environmental considerations 11.1 Introduction 11-1 11.2 Potential waterway impacts 11-2 11.2.1 General 11-2 11.2.2 Waterway integrity 11-2 11.2.3 Effects of changes in tidal exchange 11-2 11.2.4 Cause and effect of changes in catchment hydrology 11-3 11.2.5 Fauna issues 11-3 11.3 Stormwater quality management 11-3 11.3.1 General 11-3 11.3.2 Non-structural source control 11-3 11.3.3 Stormwater management system planning issues 11-3 11.3.4 Water Sensitive Urban Design 11-4 11.3.5 Water Sensitive Road Design 11-4 11.4 Structural controls (treatment techniques) 11-5 11.4.1 Selection of treatment techniques 11-5 11.5 Stormwater management plans 11-7 12. Safety aspects 12.1 General 12-1 12.2 Risk assessment 12-2 12.3 Example safety risk ranking system 12-3 12.4 Safety fencing 12-7 12.5 Inlet and outlet screens 12-9 12.5.1 General 12-9 12.5.2 Use of outlet screens 12-9 12.5.3 Site conditions where barrier fencing or inlet/outlet screens may not be appropriate 12-9 12.5.4 Inlet screen arrangement 12-10 12.5.5 Design guidelines for inlet and outlet screens 12-12 12.5.6 Hydraulics of inlet screens 12-14 12.5.7 Hydraulics of outlet screens 12-16 12.5.8 Dome inlet screens 12-17 13. Miscellaneous matters 13.1 Relief drainage or upgrading works 13-1 13.1.1 General 13-1 13.1.2 Assessment procedures and remedial measures 13-1 13.1.3 Design alternatives 13-2 13.1.4 Priority ranking 13-2 13.1.5 Design criteria 13-3 13.2 Plan presentation 13-3 13.2.1 Design drawings 13-3 13.2.2 Standard Drawings 13-4 13.2.3 As Constructed Drawings 13-4 13.3 Subsoil drainage 13-4 13.4 Scheme ranking methods 13-5 13.4.1 Triple bottom line method 13-5 13.4.2 Pseudo benefit cost analysis 13-5 13.4.3 Hurrell and Lees procedure 13-6 Queensland Urban Drainage Manual 2016 Edition xi 13.5 Symbols and abbreviations 13-7 13.6 Glossary of terms 13-13 14. References 14-1 15. Index Index-1 Appendix 1 Pipe flow design charts A1.1 Introduction Appendix 2 Structure pressure change coefficient charts A2.1 Introduction A2.2 General guidance A2.2.1 Effect of structure shape A2.2.2 Coefficients Ku and Kw (Hare charts) A2.2.3 Hare charts v. Cade and Thompson Chart A2-3 Charts A2-4 to A2-7 Charts A2-8 to A2-31 Chart A2-32 Chart A2-33 (opposing laterals) Chart A2-34 (offset laterals) Chart A2-35 Chart A2-36 Charts A2-37 and A2-38 Chart A2-39 Charts A2-40 to A2-44 Appendix 3 Road flow capacity charts Queensland Urban Drainage Manual 2016 Edition xii Preface In March 2012 the Queensland Floods Commission of Inquiry presented its final report to the Premier of Queensland. The recommendations contained within this report, specifically recommendation 10.8, suggested the Queensland Urban Drainage Manual (QUDM) be reviewed ‘to determine whether it requires updating or improvement, in particular, to reflect the current law and to take into account insights gained from the 2010/2011 floods’. This recommendation not only implied QUDM should be updated to reflect the outcomes of the Inquiry, but also any other relevant insights gained from other sources in regards to the 2010–11 floods. As a consequence of the Inquiry’s recommendations, the Department of Energy and Water Supply (DEWS) developed the 2013 Provisional Edition of QUDM. Feedback was sought on this 2013 edition, and in light of the feedback received, the Fourth Edition of QUDM has drafted. The recommendations from the Queensland Floods Commission of Inquiry’s report that are considered most relevant to the QUDM are summarised below: The need to update QUDM with respect to current legislation (Recommendation 10.8). The need for improved consideration of flows in excess of the nominated major storm (Recommendation 2.13). The need to design stormwater systems to improve the state’s resilience to extreme storm and flood events (general discussion within Chapter 2 of the report). The need for greater consideration of flood protection of essential community infrastructure and the management of flood evacuation routes (Recommendations 7.24, 7.25, 8.7, 10.11 & 10.20). Even though QUDM is not intended as a floodplain management guideline, it does provide guidance on design standards for cross drainage structures such as culverts, which is linked to the flood immunity of some evacuation routes. The need for better design guidance on preventing the flooding of commercial buildings, basements and non-habitable floors of buildings (Recommendation 7.4). The link to QUDM is through the setting of freeboards for major storm flows along roads. The need for better design guidance on the management of flood impacts on areas of manufacture or storage of bulk hazardous materials (Recommendations 7.11 & 7.13). The link to QUDM is through the design of overland flow paths that pass through industrial areas. The need for better guidance on the design and usage of stormwater backflow devices (Recommendation 10.14). Notable changes within this 2016 edition of QUDM include: A significant change in the layout of the document. A partner document, ‘A Background to QUDM’ (herein referred to as the Background Notes), was drafted that contains the bulk of the ‘discussion’, ‘explanatory notes’, ‘background theoretical work’, and ‘educational material’ that either appeared within the 2013 edition, or had been prepared during the drafting of the 2007, 2013 & 2016 editions of QUDM. This means the main QUDM document now returns to a more condensed technical document similar to its original 1992 format. Significant more discussion on the science of stormwater management, and the theory of stormwater hydrology and detention/retention systems has been introduced to the Background Notes. The lawful point of discharge test has been modified to recognise the lawful condition associated with minor changes in stormwater runoff that do not result in an actionable nuisance. Queensland Urban Drainage Manual 2016 Edition xiii The ‘Stream Velocity Method’ for estimating the Rational Method’s time of concentration for urban waterways has been modified based on an analysis of flood model data in Brisbane. Significant more information has been supplied on the application of detention and retention systems for the protection of urban waterways and aquatic ecosystems. A new method is presented for the ‘initial’ sizing of detention basins. A new section has been introduced into Chapter 7 that provides an overview of the rules and recommendations for the setting of minimum floor levels. Greater recognition is given to the differences between the design recommendations for local roads and those for state-controlled roads. The introduction of Level ‘0’ allotment drainage that improves the potential for the integration of Water Sensitive Urban Design principles into allotment drainage. An update of the Level III allotment drainage tables for allotment and roof surface areas consistent with current (2016) conditions. Update on the integration of fish passage investigations into open channel design. Introduction of a new method for improving child safety around field (drop) inlets. The QUDM partners recognise that this Manual is not a stand-alone planning and design guideline for stormwater management. It must be used in coordination with other recognised manuals covering topics such as: Floodplain management policies/guidelines Water Sensitive Urban Design Water Sensitive Road Design Natural Channel Design Waterway management including fauna passage Erosion & Sediment Control Bridge and culvert design manuals Australian Rainfall and Runoff (ARR) Australian Runoff Quality (ARQ) various Australian Standards on product manufacture and installation Whilst there are significant areas of overlap, QUDM is not intended to act as a floodplain management manual. Where appropriate, this Manual directs stormwater designers and regulators to other publications for information on floodplain management issues. The information presented within this edition of QUDM on stormwater quality treatment and the management of environmental impacts is not comprehensive and should not be used to supersede other more comprehensive and locally relevant manuals and guidelines. Queensland Urban Drainage Manual 2016 Edition xiv Acknowledgments The preparation of the original 1992 edition was commissioned jointly by the Queensland Department of Primary Industries (Water Resources), the Institute of Municipal Engineering Australia (Queensland Division) and the Brisbane City Council. Funding for the drafting of this fourth edition was supplied by the Queensland Government, Department of Energy and Water Supply. Review Panel (fourth edition, 2016): Ross Guppy (Chair), Institute of Public Works Engineering Australasia (Queensland Division) Russell Cuerel, Department of Energy and Water Supply Tony Loveday, RMA Engineers Pty Ltd Neil McKee Phil McKone, Livingstone Shire Council Hamid Mirfenderesk, City of Gold Coast Ouswatta Perera, Brisbane City Council Richard Priman, Department of Energy and Water Supply Chris Russell, Department of Transport and Main Roads Frank Scheele, South Burnett Regional Council David Simpson, Brisbane City Council Grant Witheridge, Catchments & Creeks Pty. Ltd. (redraft and artwork) Sarah Hausler, McCullough Robertson Lawyers (review of Chapter 3) Project team (third edition, 2013): Russell Cuerel, Department of Energy and Water Supply Upali Jayasinghe, Department of Energy and Water Supply Grant Witheridge, Department of Energy and Water Supply Steering committee members (second edition, 2007): Bob Adamson, Brisbane City Council Peter Barnes, Brisbane City Council Suzanna Barnes-Gillard, Institute of Public Works Engineering Australia Russell Cuerel, Department of Natural Resources and Water Neville Gibson, Brisbane City Council Allan Herring, Pine Rivers Shire Council Upali Jayasinghe, Department of Natural Resources and Water Graham Jenkins, Queensland University of Technology Chris Lawson, Connell Wagner Patrick Murphy, Boonah Shire Council Geoff Stallman, Environmental Protection Agency Bill Weeks, Department of Main Roads Grant Witheridge, Catchments & Creeks Pty. Ltd. (first draft and artwork) Steering committee members (first edition, 1992): Mr R I Rees, Department of Primary Industries, Water Resources Mr R Priman, Department of Primary Industries, Water Resources Mr J F Jolly, Institute of Municipal Engineering Australia, Queensland Division Mr L M Yates, Institute of Municipal Engineering Australia, Queensland Division Mr T W Condon, Brisbane City Council Mr R A Halcrow, Brisbane City Council Mr D G Carroll, Brisbane City Council Queensland Urban Drainage Manual 2016 Edition xv Project team (first edition, 1992): Mr N D Jones, Neville Jones & Associates Pty Ltd Mr G M Anderson, Neville Jones & Associates Pty Ltd Mr C H Lawson, B.E.(Hons.), Neville Jones & Associates Pty Ltd Mr D G Ogle, Australian Water Engineering Mr B C Tite, Australian Water Engineering The following images (2016 edition) have been supplied courtesy of Catchments & Creeks Pty Ltd and remain the property of Catchments & Creeks Pty Ltd: 7.5.4, 7.5.5, 7.5.6, 7.5.7, 7.6.1, 7.6.2, 7.6.3, 7.6.4, 7.16.4(a), (b) & (c), 7.16.9(a) & (b), 7.16.10, 7.16.11, 7.16.12, 7.16.13, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 8.10, 8.11, 8.12, 8.13, 9.2, 10.4, 10.5, 10.6, 10.7, 10.8, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.13, 12.16. BN4.4.1, BN4.4.2, BN4.4.3, BN 4.6.11.1, BN 4.6.11.2, BN 4.6.11.3, BN 4.6.11.4, BN 4.6.11.5, BN 4.6.11.6, BN 4.6.11.7, BN 4.6.11.8, BN 4.6.11.9, BN 4.6.11.10, BN 4.6.11.11, BN 4.6.11.12, BN 5.4.1, BN 5.4.2, BN 7.16.4(a)&(b), BN 7.16.5(a)&(b), BN 7.16.6(a)&(b), BN 7.16.7(a)&(b), BN 8.3.1, BN 8.7.1, BN 8.7.2, BN 8.7.3, BN 8.7.4, BN 8.7.5, BN 8.7.6, BN 8.7.7, BN 8.7.8, BN 8.7.9, BN 8.7.10, BN 9.8, BN 9.9, BN 9.10, BN 9.11, BN 9.12, BN 9.13, BN 9.14, BN 9.15, BN 10.4.1, BN 10.4.2, BN 10.4.3, BN 10.4.4, BN 10.4.5, BN 12.5.1. Photos: BN 9.5.1, 9.5.2. Queensland Urban Drainage Manual 2016 Edition xvi List of tables Table 2.2.1 Key stormwater design parameters and desired outcomes 2-4 Table 3.15.1 Example of possible statutory approvals 3-18 Table 4.5.1 Fraction impervious vs. development category 4-7 Table 4.5.2 Table of frequency factors 4-8 Table 4.5.3 Table of C10 values 4-8 Table 4.5.4 C10 values for zero fraction impervious 4-8 Table 4.6.1 Summary of typical components of time of concentration 4-10 Table 4.6.2 Recommended standard inlet times 4-11 Table 4.6.3 Recommended roof drainage system travel times 4-12 Table 4.6.4 Recommended maximum length of overland sheet flow 4-13 Table 4.6.5 Surface roughness or retardance factors 4-14 Table 4.6.6 Modified Stream Velocity method for catchment areas of 5 to 100 km2 4-21 Table 4.9.1 Typical single storm event volumetric runoff coefficients for various Soil Hydrologic Groups 4-24 Table 4.9.2 Typical infiltrations rates for various Soil Hydrological Groups 4-25 Table 5.5.1 Summary of design requirements for detention/retention systems 5-6 Table 5.6.1 Recommended initial loss values for use in sizing detention basins 5-7 Table 5.6.2 Typical infiltrations rates for various soil hydrologic groups 5-8 Table 5.6.3 Selection of initial loss values for different design functions 5-8 Table 5.7.1 Guidelines for basin freeboard requirements 5-11 Table 5.9.1 Criteria for basin outlet structures 5-13 Table 5.10.1 Recommendations for extreme flood 5-14 Table 5.10.2 Hazard categories for referable dams 5-15 Table 7.3.1 Recommended design average recurrence intervals (ARI) and annual exceedence probabilities (AEP) for the minor system 7-5 Table 7.3.2 Recommended design average recurrence intervals (ARI) and annual exceedence probabilities (AEP) for the combined minor/major system 7-5 Table 7.3.3 Development categories 7-7 Table 7.3.4 Summary of design requirements for overland flow paths 7-8 Table 7.3.5 Flow depth and width limitations for the minor storm 7-14 Table 7.3.6 Flow depth and width limitations for the major storm 7-14 Table 7.4.1 Recommended design storm for road drainage design 7-17 Table 7.4.2 Flow limits for 'longitudinal' flow during MINOR STORM 7-18 Table 7.4.3 Flow limits for 'transverse' flow during MINOR STORM 7-18 Table 7.4.4 Flow limits for 'longitudinal' flow during MAJOR STORM 7-19 Table 7.4.5 Flow limits for 'transverse' flow during MAJOR STORM 7-19 Table 7.4.6 Recommended values of Manning's roughness coefficient and flow correction factor for use in Izzard's equation 7-22 Table 7.5.1 Provision for blockage at kerb inlets 7-23 Table 7.6.1 Recommended maximum spacing of access chambers 7-31 Table 7.6.2 Recommended maximum reduction in pipe size - SINGLE PIPES 7-32 Table 7.8.1 Recommended minimum spacing of multiple pipes 7-38 Queensland Urban Drainage Manual 2016 Edition xvii Table 7.10.1 Recommended minimum cover over pipes 7-41 Table 7.11.1 Acceptable flow velocities for pipes and box sections 7-42 Table 7.12.1 Acceptable pipe grades for pipes flowing full 7-43 Table 7.13.1 Design of roof gutters and downpipes 7-44 Table 7.13.2 Design storm for underground allotment drainage (not roof drainage) 7-44 Table 7.13.3 National construction codes relating to allotment drainage 7-47 Table 7.13.4 Design recommendations for rear of allotment, inter-allotment drainage systems 7-51 Table 7.13.5 Design standard for Level 0 drainage system 7-53 Table 7.13.6 Design standard for Level I drainage system 7-54 Table 7.13.7 Design standard for Level II drainage system 7-55 Table 7.13.8 Recommended design criteria for Level II rear of allotment drainage system 7-56 Table 7.13.9 Design standard for Level III drainage system 7-57 Table 7.13.10 Recommended design criteria for Level III rear of allotment drainage system 7-58 Table 7.13.11 Design standard for Level IV drainage system 7-59 Table 7.13.12 Design standard for Level V drainage system 7-60 Table 7.16.1 Minimum freeboard recommendations for kerb inlets and pits 7-66 Table 7.16.2 Application of freeboard recommendations 7-67 Table 7.16.3 Recommended values for surface roughness (average pipe condition) 7-68 Table 7.16.4 Potential decrease in pressure change coefficient as a result of benching 7-70 Table 7.16.5 Entrance (energy) loss coefficients 7-72 Table 7.16.6 Pressure loss coefficients at mitred fittings 7-74 Table 7.16.7 Energy loss coefficients for flow expansions and contractions within pipes 7-77 Table 7.16.8 Pressure change coefficients for expansions and contractions 7-77 Table 7.16.9 Mitre bend outlet length correction factor 7-80 Table 7.16.10 Trial values of KU for use in determining HGL under partially full flow conditions7-82 Table 8.3.1 Suggested tailwater levels for discharge to tidal waterways 8-3 Table 8.5.1 Minimum and maximum desirable elevation of pipe outlets above receiving water bed level for ephemeral waterways 8-15 Table 8.7.1 Typical bank scour velocities 8-18 Table 8.7.2 Minimum thickness (T) of rock pad 8-21 Table 9.2.1 Typical attributes of various constructed drainage channels 9-4 Table 9.3.1 Recommended channel freeboard 9-6 Table 9.3.2 Typical minimum design roughness values for vegetated channels 9-7 Table 9.3.3 Manning's roughness of rock lined channels with shallow flow 9-8 Table 9.3.4 Manning's roughness for grassed channels (50-150 mm blade length) 9-8 Table 9.3.5 Channel transition energy loss coefficients (C u) 9-10 Table 9.5.1 Suggested permissible flow velocities for water passing through/over vegetation 9-13 Table 9.5.2 Maximum permissible velocities for consolidated bare earth channels and grassed channels 9-14 Table 9.5.3 Suggested maximum bank gradient 9-15 Table 9.8.1 Low-flow channels within grassed or hard-lined channels 9-21 Table 9.9.1 Typical thickness (T) of two rock layers 9-23 Queensland Urban Drainage Manual 2016 Edition xviii Table 9.9.2 Recommended rock sizing equation for non-vegetated rock-lined drains 9-24 Table 9.9.3 Recommended K-values for use in rock sizing equations 9-25 Table 9.9.4 Recommended rock sizing equations for rock-lined batter chutes 9-25 Table 9.9.5 Recommended safety factor for use in determining rock size 9-25 Table 9.9.6 Recommended distribution of rock size for constructed riffles 9-27 Table 9.9.7 Recommended rock sizing equation for partially drowned waterway chutes 9-28 Table 9.9.8 Recommended safety factor for use in designing waterway and gully chutes 9-29 Table 9.9.9 Waterway chutes: uniform flow conditions, sr = 2.4, d50/d90 = 0.5, 'SF = 1.2' 9-30 Table 9.9.10 Waterway chutes: uniform flow conditions, sr = 2.4, d50/d90 = 0.5, 'SF = 1.5' 9-31 Table 10.1.1 Suggested blockage factors for bridges 10-1 Table 10.4.1 Suggested blockage factors for culverts 10-9 Table 12.1.1 Flow hazard regimes for infants, children and adults 12-2 Table 12.3.1 Contact classification 12-3 Table 12.3.2 Potential safety risks associated with a conduit flowing full 12-3 Table 12.3.3 Potential safety risks associated with the length of the conduit 12-4 Table 12.3.4 Potential safety risks associated with flow conditions within a conduit 12-4 Table 12.3.5 Potential safety risks associated with flow conditions at the outlet of a conduit 12-5 Table 12.3.6 Risk ranking matrix 12-5 Table 12.3.7 A guide to mitigation options for various safety risks 12-6 Table 12.5.1 Potential beneficial and adverse consequences of inlet and outlet screens 12-9 Table 12.5.2 Maximum clear spacing of vertical bars 12-12 Table 12.5.3 Recommended slope of inlet safety screens 12-12 Table 12.5.4 Advantages and safety risks associated with dome inlet screens 12-17 Table 12.5.5 Standard dimensions of dome inlet safety screen 12-19 Queensland Urban Drainage Manual 2016 Edition xix List of figures Figure 4.1 Application of standard inlet time 4-11 Figure 4.2 Typical roof drainage systems (residential) 4-12 Figure 4.3 Typical roof drainage systems (industrial) 4-12 Figure 4.4 Overland sheet flow times (shallow sheet flow only) 4-13 Figure 4.5 Flow travel time in pipes and channels 4-16 Figure 4.6 Kerb and channel flow time using Manning’s equation 4-17 Figure 4.7 Kerb and channel flow velocity using Izzard’s equation 4-18 Figure 4.8 Derivation of the equal-area slope (Se) of main stream 4-21 Figure 5.1 Additional temporal patterns for use in design of embankments and high-level outlets 5-10 Figure 5.2 Typical basin outlets for small basins 5-12 Figure 7.3.1 Flow chart for the determination of minimum floor levels for Class 1 buildings7-12 Figure 7.3.2 Major storm flow design criteria 7-15 Figure 7.3.3 Major storm flow design criteria 7-16 Figure 7.4.1 Typical flow width criteria (minor storm) 7-20 Figure 7.4.2 Half road flow 7-22 Figure 7.5.1 Flow chart for determining kerb inlet positions on-grade 7-25 Figure 7.5.2 A sag in a road with supercritical approach flows 7-26 Figure 7.5.3 Limiting condition for a sag inlet to act as an on-grade inlet (n = 0.013) 7-26 Figure 7.5.4 Field inlet operating under weir flow 7-28 Figure 7.5.5 Field inlet operating under free (atmospheric) orifice flow 7-29 Figure 7.5.6 Field inlet operating under fully drowned (non-atmospheric) conditions 7-29 Figure 7.5.7 Minimum lip width required for scour protection 7-30 Figure 7.6.1 Flow lines resulting from inflow pipe directed at pit centre 7-32 Figure 7.6.2 Inflow pipe directed at centre of outflow pipe 7-32 Figure 7.6.3 Bellmouth entrance to outlet pipe 7-32 Figure 7.6.4 Inlet chamber showing water level well above outlet obvert 7-32 Figure 7.13.1 (a) to (e) Levels of roof and allotment drainage system 7-45 Figure 7.13.1 (f) Level V of roof and allotment drainage system 7-46 Figure 7.13.2 (a) Inter-allotment drainage systems – Option 1 7-49 Figure 7.13.2 (b) Inter-allotment drainage systems – Option 2 7-49 Figure 7.16.1 Hydraulics for a single pipe reach 7-64 Figure 7.16.2 (a) Tailwater above obvert 7-65 Figure 7.16.2 (b) Tailwater below obvert 7-65 Figure 7.16.2 (c) Tailwater below pipe invert 7-65 Figure 7.16.3 Nomenclature at structures 7-69 Figure 7.16.5 (a) Projecting from fill 7-71 Figure 7.16.5 (b) Headwall with wing walls 7-71 Figure 7.16.5 (c) Mitred to conform to fill slope 7-71 Figure 7.16.5 (d) Hooded entrance 7-71 Figure 7.16.6 Bend loss coefficients 7-74 Figure 7.16.7 Penetration loss coefficients 7-75 Figure 7.16.8 Branch line nomenclature 7-76 Figure 7.16.9 Flow conditions for sudden expansion and contraction 7-76 Queensland Urban Drainage Manual 2016 Edition xx Figure 7.16.10 Surcharge chamber with or without an outlet pipe 7-78 Figure 7.16.11 Surcharge chamber with multiple inflow pipes 7-78 Figure 7.16.12 Surcharge chamber with outlet pipe of equivalent size 7-79 Figure 7.16.13 Surcharge chamber with smaller low-flow outlet pipe 7-79 Figure 7.16.14 HGL determination for pipes flowing partially full 7-81 Figure 8.1 Tidal variations 8-1 Figure 8.2 Tidal channel with high level bypass channel 8-6 Figure 8.3 Possible arrangement of sediment backflow control device in coastal zones 8-8 Figure 8.4 Minimum desirable outlet setback 8-10 Figure 8.5 Discharge to swale or spoon drain 8-12 Figure 8.6 Recommended scour protection at crest of drop chutes 8-12 Figure 8.7 Partial discharge through a surcharge chamber 8-13 Figure 8.8 Discharge into constructed outlet channel 8-14 Figure 8.9 Outlet channel with benching to allow flow bypassing of a heavily vegetated low-flow channel 8-14 Figure 8.10 Discharge directly into a watercourse 8-15 Figure 8.11 Sizing of rock pads for 'single' pipe outlets 8-19 Figure 8.12 Sizing of rock pads for 'multiple' pipe outlets 8-20 Figure 8.13 Typical layout of a rock pad outlet structure 8-21 Figure 9.1 Channel freeboard 9-6 Figure 9.2 Introduction of bypass channels on tidal drains 9-15 Figure 10.1 Subcritical flow with subcritical tailwater 10-2 Figure 10.2 Subcritical flow with critical depth at tailwater 10-2 Figure 10.3 Combined subcritical and supercritical flow 10-3 Figure 10.4 Example of overtopping flows at an urban culvert crossing 10-5 Figure 10.5 Minimum desirable flow depth to achieve fish passage 10-7 Figure 10.6 Multi-cell culvert with 'wet' and 'dry' cells 10-8 Figure 10.7 Culvert inlet with debris deflector walls 10-10 Figure 10.8 Floodplain culvert adjacent a bridge crossing 10-11 Figure 12.1 Dome inlet screen 12-10 Figure 12.2 Major inlet structure 12-10 Figure 12.3 Hinged inlet bar screen 12-10 Figure 12.4 Bar screen with upper stepping board inlet screen 12-11 Figure 12.5 Fixed stepping board inlet screen 12-11 Figure 12.6 Alternative major inlet structure 12-11 Figure 12.7 Design requirements for inlet screens 12-13 Figure 12.8 Inlet screen mounted away from the inlet 12-14 Figure 12.9 Inlet screen mounted close to the inlet 12-15 Figure 12.10 Outlet screen with minimal blockage 12-16 Figure 12.11 Partially blocked outlet screen 12-16 Figure 12.12 Outlet screen mounted away from the outlet 12-17 Figure 12.13 Minimum internal lip width requirements of dome safety inlet screen 12-18 Figure 12.14 Straight-edged drop inlet 12-19 Figure 12.15 Drop inlet with raised lip 12-19 Figure 12.16 Diagrammatic representation of approach flow angle (plan view) 12-20 Queensland Urban Drainage Manual 2016 Edition xxi Appendix 1 – Pipe flow design charts A1-1 Pipe flow capacity chart (Manning's equation) A1-2 Pipe flow capacity chart (Manning's equation) A1-3 Hydraulic elements for pipes flowing partially full Appendix 2 – Structure pressure change coefficient charts A2-1 Index to pressure change coefficient charts A2-2 Index to pressure and energy loss analysis charts A2-3 Pressure head change coefficients for rectangular inlet with grate flow only modified from DOT (1992) A2-4 Pressure head change and water surface elevation coefficients for straight through flow for submergence ratio, S/Do = 2.5 (Source: Hare, 1980) A2-5 Pressure head change and water surface elevation coefficients for 22.5o bends at pit junctions, with branch point on downstream face of pit, and for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-6 Pressure head change and water surface elevation coefficients for 45o bends at pit junctions with branch point located on downstream face of pit for a submergence ratio, S/Do = 2.5 (Source: Hare, 1980) A2-7 Pressure head change and water surface elevation coefficients for 45o bends at pit junctions with branch point located on downstream face of pit for a submergence ratio, S/Do = 2.5 (Source: Hare, 1980) A2-8 Pressure head change coefficients (Ku) for 22.5o bends at pit junctions with branch point located on the upstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-9 Pressure head change coefficients (Ku) for 22.5o bends at pit junctions with branch point located on the upstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-10 Water surface elevation coefficients (Kw) for 22.5o bends at pit junctions with branch point located on the upstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-11 Water surface elevation coefficients (Kw) for 22.5o bends at pit junctions with branch point located on the upstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-12 Pressure head change coefficients (Ku) for 45o bends at pit junctions with branch point located on the upstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-13 Pressure head change coefficients (Ku) for 45o bends at pit junctions with branch point located on the upstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-14 Water surface elevation coefficients (Kw) for 45o bends at pit junctions with branch point located on the upstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-15 Water surface elevation coefficients (Kw) for 45o bends at pit junctions with branch point located on the upstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-16 Pressure head change coefficients (Ku) for 45o bends at pit junctions with branch point located on the upstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-17 Pressure head change coefficients (Ku) for 45o bends at pit junctions with branch point located on the upstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) Queensland Urban Drainage Manual 2016 Edition xxii A2-18 Water surface elevation coefficients (Kw) for 45o bends at pit junctions with branch point located on the upstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-19 Water surface elevation coefficients (Kw) for 45o bends at pit junctions with branch point located on the upstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-20 Pressure head change coefficients (Ku) for 67.5o bends at pit junctions with branch point located near the downstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-21 Pressure head change coefficients (Ku) for 67.5o bends at pit junctions with branch point located near the downstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-22 Water surface elevation coefficients (Kw) for 67.5o bends at pit junctions with branch point located near the downstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-23 Water surface elevation coefficients (Kw) for 67.5o bends at pit junctions with branch point located near the downstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-24 Pressure head change coefficients (Ku) for 67.5o bends at pit junctions with branch point located near the upstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-25 Pressure head change coefficients (Ku) for 67.5o bends at pit junctions with branch point located near the upstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-26 Water surface elevation coefficients (Kw) for 67.5o bends at pit junctions with branch point located near the upstream face of pit for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-27 Water surface elevation coefficients (Kw) for 67.5o bends at pit junctions with branch point located near the upstream face of pit for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-28 Pressure head change coefficients (Ku) for 90o bends at pit junctions for a submergence ratio S/Do = 2.5 (Source: Hare, 1980) A2-29 Pressure head change coefficients (Ku) for 90o bends at pit junctions for submergence ratios S/Do = 1.5, 2.0, 3.0 and 4.0 (Source: Hare, 1980) A2-30 Water surface elevation coefficients (Kw) for 90o bends at pit junctions for a submergence ratio, S/Do = 2.5 (Source: Hare, 198

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