NATURE BASED SOLUTIONS Using rainwater as a resource to create resilient and liveable cities INSIDE THIS WHITE PAPER Managing rainwater with Nature Based Solutions Cross-disciplinary collaboration in climate adaptation Urban recirculation of rainwater 2 Nature Based Solutions Using rainwater as a resource to create resilient and liveable cities Version 2.0 February 2021 Front page photo Climate adaptation at Taasinge Plads in Copenhagen Photo: Kontraframe Editor in Chief State of Green Malene Bering Beitzel, [email protected] Technical Editors Water Vision Denmark / KLAR Utility Hanne Kjær Jørgensen, [email protected] Danish Technological Institute / DNNK, Danish Network for Climate Adaptation Ulrik Hindsberger, [email protected] Contributors 1:1 Landskab Jacob Kamp, [email protected] Amphi Consult Lars Briggs, [email protected] Aarhus Vand Anne Laustsen, [email protected] Aarhus Vand Pia Jacobsen, [email protected] BOGL Dorte Hermann, [email protected] Byggros Louise Hansen, [email protected] City of Copenhagen Lykke Leonardsen, [email protected] City of Copenhagen (Skt. Kjelds Kvarter) René Sommer Lindsay, [email protected] DHI Morten Just Kjølby, [email protected] HOFOR - Greater Copenhagen Water Utility Martin Vester, [email protected] LYTT Architecture Jacob Fischer, [email protected] NCC Brask Michael, [email protected] NIELS LÜTZEN landskabsarkitekter Niels Lützen, [email protected] NIRAS Jan Jeppesen, [email protected] NIRAS Jens Brandt Bering, [email protected] NIRAS Rikke Juul Monberg, [email protected] Novafos Tina Otterstrøm Jensen, [email protected] Pilebyg Vibe Gro Falk, [email protected] Ramboll Martin Zoffmann, [email protected] SLA Kristoffer Holm Pedersen, [email protected] The Climate City Bjarne Rasmussen. [email protected] THIRD NATURE Flemming Rafn, [email protected] University of Copenhagen Marina Bergen Jensen, [email protected] Watercare Kristian Bruun Nielsen, [email protected] Wavin Henning Nykjær Stabell, [email protected] WSP Jesper Fog, [email protected] WSP Mads Poulsen, [email protected] Download this white paper Download this white paper and other related publications at www.stateofgreen.com/publications For more information To order copies of this white paper or receive information about other related publications, please contact State of Green at [email protected] Copyright State of Green 2021 EXecutive summary 3 EXECUTIVE SUMMARY Population growth, increasingly polluted drinking water, floodings and more frequent and longer periods of droughts all encourage an optimised use of rainwater in cities. Climate adaptation seeks to lower the risks posed by the consequences of climate change, including flooding that arises from extreme rain events. However, when approached holistically it can also be used to create synergies between a number of urban challenges by addressing several areas of urban development at the same time e.g. turning urban areas green, whilst at the same time reducing heat islands. In this respect, Nature Based Solutions (NBS) can play a key role in urban water management and contribute to building cities that are attractive for people to live, work and play in. This white paper features lessons learned from a range of Danish stakeholders within rainwater management and NBS. It is supported by state-of-the art case examples demonstrating how rainwater can be used as a resource to create more resilient and liveable cities. Multifunctional solutions create more resilient and liveable cities A large number of synergies and cost-efficiencies can be achieved when rainwater management is integrated into overall urban planning. Cities around the world are increasingly concerned with becoming more resilient to the effects of climate change, including reducing the risk of flooding and rising temperatures. At the same time, many cities are focusing on securing an ample supply of clean drinking water that can sustain a growing population. Denmark is working towards creating multifunctional solutions which – in addition to managing rainwater and reducing the risk of flooding – also create added value for cities as they contribute to maintaining a sustainable water balance and result in new, attractive recreational areas. Find inspiration for your own NBS projects The content of this white paper is intended as a tool for international stakeholders who wish to gain insight into the many potentials of using Nature Based Solutions, gain an overview of how solutions have been implemented in Denmark and around the world, or who are looking for Danish partners to collaborate with on projects in their own country. We hope you will be inspired. 4 FOREWORD SHAPING TOMORROW’S CITIES THROUGH NATURE BASED SOLUTIONS “Denmark’s experience shows that climate adaptation and rainwater management can be turned into an opportunity to create not only more resilient but also more liveable cities” Lea Wermelin, Minister for Environment, Denmark As the climate changes and the number create more climate resilient cities are well Based Solutions can contribute to making and frequency of rainfall events increases, underway in Denmark where we have had cities not only more resilient to climate so does the need for intelligent rainwater with a national action plan for a National change but also more attractive places to management solutions. Like many other Action Plan for a Climate-Proof Denmark live. countries, Denmark has experienced since 2012. Today, all municipalities must the consequences of a changing climate have a local climate adaptation plan, which The best examples of Nature Based first-hand. Over the past decade, we have addresses the specific climate change-re- Solutions succeed in solving more than witnessed extreme rain events that have lated risks in their area. one problem at the same time. Holistic caused flooding and damages to homes as solutions, however, require close collabo- well as infrastructure. Nature Based Solutions ration between authorities, water utilities, More and more Danish cities and water organizations, private companies and According to the Fifth Assessment Report utilities are looking into managing rain- individuals. Denmark has a long tradition of from the IPCC, we can expect even more fre- water as close to the source as possible such collaboration. This has brought us far. quent and more extreme weather events in and diverting it away from the sewerage We are proud of our results and solutions. the years to come. Finding new and innova- systems and wastewater treatment plants, And we are eager to share our experiences tive solutions to managing rainwater in our thereby bringing down the risk of combined and lessons learned with other countries. cities should therefore be a focal point for sewer overflows. Solutions that manage cities and water utilities around the world. increasing volumes of rainwater span from Join us in Copenhagen for the IWA hydraulic models for the planning phase to World Water Congress & Exhibition Increasing pressure on sewerage solutions for local detention of rainwater Denmark will be hosting the IWA World systems such as subsurface infiltration beds, green Water Congress & Exhibition in September Increasing precipitation caused by climate roofs and permeable paving, to drainage 2022. I invite you to join us for a week of in- change is putting greater pressure on our solutions such as separate sewers for teresting discussions on how we can shape sewerage systems. However, rather than rainwater and sewage water as well as local our water future together. simply replacing existing pipes with larger rainwater treatment via roadside infiltra- ones, benefits can be achieved by focusing tion beds etc. Until then, I hope you will be inspired by the on more intelligent rainwater management many solutions in this white paper. which detains the rainwater in existing Multipurpose solutions enrich the city structures or distributes it to areas where By combining climate adaptation measures it creates the least damage. Efforts to with exciting urban development, Nature INDEX 5 INDEX 1. From climate adaptation to green urban development ..................................................6 Using rainwater as a resource 2. Managing rainwater with Nature Based Solutions .........................................................8 NBS a tool for climate change adaptation and increasing urban biodiversity 3. Cross-disciplinary collaboration in climate adaptation ................................................10 Creating synergies and saving costs through collaboration between different stakeholders 4. Nature Based Solutions in simulation models ...............................................................12 Assessing the urban water cycle and the impact of NBS 5. Breaking through the surface .........................................................................................14 Managing rainwater in densely populated areas with impermeable paving 6. Increasing urban biodiversity ........................................................................................16 Creating green corridors and resilient cities by integrating nature into urban life 7. Nature Based Solutions and treatment of runoff ..........................................................18 Improving the water cycle by ensuring an appropriate quality of rainwater runoff 8. Urban recirculation of rainwater ................................................................................... 20 Using rainwater harvesting to create a city in water balance 9. Creating resilient and liveable cities