URBAN CLIMATE CHANGE GUIDELINES HOW TO ACHIEVE SUSTAINABLE ADAPTATION IN URBAN AREAS. JANUARY 2012 CONTENTS 1 Introduction ______________________________________________________________ 1 1.1 Background _________________________________________________________________ 1 1.2 Purpose ____________________________________________________________________ 2 1.3 Definition of the problem ______________________________________________________ 3 1.4 An Example – Legislation in Denmark _____________________________________________ 4 1.4.1 Sewerage plan ______________________________________________________________________ 4 1.4.2 Sewer renewal plan __________________________________________________________________ 5 1.4.3 Contingency plan ____________________________________________________________________ 5 1.4.4 Additional municipal planning, local plans, plans for water quality, etc. ________________________ 5 1.4.5 Risk assessment and analysis of extreme rain _____________________________________________ 6 1.5 The EU Flood Directive ________________________________________________________ 6 1.5.1 Preliminary flood risk assessment ______________________________________________________ 7 1.5.2 Flood hazard and flood risk maps _______________________________________________________ 7 1.5.3 Flood risk management plans __________________________________________________________ 8 1.5.4 Publication of maps, plans, etc. ________________________________________________________ 8 1.5.5 Summary __________________________________________________________________________ 8 2 Status of knowledge on climate change _______________________________________ 10 2.1 Scenarios for future climate change _____________________________________________ 10 2.2 Data base for the analysis of climate change impacts on drainage systems _____________ 13 2.3 Future rain over Denmark _____________________________________________________ 13 2.4 Future water levels in marine waters ____________________________________________ 15 2.5 Future water levels in lakes and rivers ___________________________________________ 15 2.6 Future water levels / pressures in groundwater ___________________________________ 16 2.7 Determination of input data and boundary conditions - Recommendations _____________ 16 2.7.1 Choice of precipitation ______________________________________________________________ 16 2.7.2 Coupled rainfall ____________________________________________________________________ 17 2.7.3 Choice of downstream boundary condition – Future water levels in recipients of storm water systems 18 2.7.4 Sea level rise and climate-related extreme water levels ____________________________________ 18 2.7.5 Rivers, lakes and ground water zone ___________________________________________________ 18 3 Compliance with the performance requirements under the influence of climate change 20 3.1 Description of desired standard of services _______________________________________ 20 3.1.1 Service level and compliance with operational requirements under the influence of climate change 23 4 Modelling of flooding from storm water system and rivers ________________________ 25 4.1 From surface depression maps to sophisticated hydraulic models _____________________ 25 4.1.1 Model tools _______________________________________________________________________ 25 4.1.2 Decision making process _____________________________________________________________ 26 4.1.3 The multidisciplinary angle ___________________________________________________________ 26 4.1.4 Economy _________________________________________________________________________ 26 4.2 Calculation Methods _________________________________________________________ 27 4.2.1 Terrain model - QA _________________________________________________________________ 28 4.2.2 Surface depression maps ____________________________________________________________ 29 4.2.3 Hydraulic surface calculations _________________________________________________________ 33 4.2.4 Hydrodynamic drainage model 1D _____________________________________________________ 35 The Climate Cookbook – 2nd Edition i Greve Forsyning, VandCenter Syd, , PH-Consult og DHI © DHI 2012 4.2.5 Combined hydrodynamic drainage model and surface model 1D-1D__________________________ 35 4.2.6 Combined hydrodynamic drainage model and surface model 1D-2D__________________________ 40 4.3 Comparison of methods ______________________________________________________ 42 5 Flooding from the sea ______________________________________________________ 45 5.1 Calculation Methods _________________________________________________________ 45 5.1.1 Water elevation map ________________________________________________________________ 46 5.1.2 Water elevation map in connection to the sea ___________________________________________ 48 5.1.3 1D-urban drainage systems __________________________________________________________ 50 5.1.4 1D-1D two-layered hydrodynamic model _______________________________________________ 50 5.1.5 Hydrodynamic calculation of flood _____________________________________________________ 50 5.1.6 1D-2D hydrodynamic modelling of the flow on terrain combined with a hydrodynamic model of the drainage system __________________________________________________________________________ 53 6 Urban climate adaptation __________________________________________________ 55 6.1 Risk analysis ________________________________________________________________ 55 6.1.1 Damage assessment using a risk analysis ________________________________________________ 55 6.1.2 Risk analysis _______________________________________________________________________ 56 6.1.3 Risk of flooding from extreme rainfall __________________________________________________ 58 6.2 Priority adapting to floods under a changing climate _______________________________ 62 6.2.1 Urban prioritization in Greve municipality _______________________________________________ 63 6.2.2 Description of the method for prioritization in Greve ______________________________________ 63 6.2.3 Quality assurance of priority __________________________________________________________ 64 6.3 Options for adapting the urban drainage system __________________________________ 65 6.3.1 Physical measures on drainage system _________________________________________________ 65 6.3.2 Infiltration of storm water ___________________________________________________________ 66 6.3.3 Separation of combined systems ______________________________________________________ 66 6.3.4 Increasing pipe sizes ________________________________________________________________ 67 6.3.5 Overflow _________________________________________________________________________ 67 6.3.6 Basins ____________________________________________________________________________ 68 6.3.7 Local storage ______________________________________________________________________ 68 6.3.8 Control and regulation of drainage system ______________________________________________ 68 6.3.9 Use of the road system ______________________________________________________________ 69 6.3.10 Augmentation on private property __________________________________________________ 69 6.3.11 Drainage of road space ____________________________________________________________ 71 6.3.12 Examples of local handling of rainwater ______________________________________________ 71 6.4 Flood emergency preparedness ________________________________________________ 73 6.4.1 Before the rainfall event _____________________________________________________________ 74 6.4.2 During the rainfall event _____________________________________________________________ 78 6.4.3 After the rainfall event ______________________________________________________________ 78 7 Summary and conclusion ___________________________________________________ 79 8 References _______________________________________________________________ 81 APPENDIX A Odense – Sports Arena B Climate Analysis of Greve Midt and Karlslunde The Climate Cookbook – 2nd Edition ii Greve Forsyning, VandCenter Syd, , PH-Consult og DHI © DHI 2012 Disclaimer The information contained in this Guideline report is for general information purposes only. 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The inclusion of any links does not necessarily imply a recommendation or endorse the views expressed within them. The Climate Cookbook – 2nd Edition iii Greve Forsyning, VandCenter Syd, , PH-Consult og DHI © DHI 2012 1 INTRODUCTION 1.1 Background This document describes how cities around The World can respond to flooding problems expected due to impact from climate change. These guidelines provide an overview of information available about climate