Od hrozby k příležitosti - zhodnocení nakládání se srážkovými vodami v urbanizovaných (městských) územích
From threat to opportunity – revaluating storm water in urban areas
Storm water has long been considered an obstacle with negative effects on movement and health in urban areas. But an increased focus on sustainability has led us to revaluate the role of storm water. The report “From threat to opportunity – revaluating storm water management in urban areas” investigates how sustainable storm water management can contribute to the creation of liveable cities.
There are various approaches to managing excess water originating from rain and snowfall. It traditionally includes drainage of water through infrastructure such as sewers, but increasingly sophisticated sustainable approaches with various “Blue-Green Infrastructure” measures are needed. Without effective storm water management, it could cause flooding affecting the lives of the citizens living, working and moving through urban areas, and prevent the movement of goods and information. Sustainable storm water management combines conventional “hard” engineering with “soft” landscaping – to create Blue-Green infrastructure that uses storm water as an asset for green cities.
To ensure sustainable quality of life in liveable and attractive cities, we need to utilize many different ideas and perspectives on storm water management from storm water professionals as well as citizens. The Blue-Green Infrastructure (BGI) approach is of importance in securing a sustainable future and generating multiple benefits in the environmental, ecological, social and cultural spheres.
Sustainable storm water management requires a co-ordinated interdisciplinary approach to water and green space management from institutional organisations, industry, academia, and local communities and stakeholders. Sustainable Drainage Systems (SuDS) manage storm water as close as possible to the place it falls and mimic natural processes. Depending on the scale of the solution, an integrated storm water system could consist of “natural” measures like green roofs, planters, green belts, swales, wetlands, grassed dry retention ponds or raingardens combined usually with other, more “artificial” measures, for example underground infiltration or/and detention and retention tanks etc. BGI helps to reduce flooding and the effects of climate change in urban areas.
Storm water should not be considered as a threat, but rather as a positive landscape element that, together with vegetation, constitutes protective temperature islands in cities. The BGI approach significantly influences city transport and the strategy of human mobility planning in general. This calls for deep, well-timed and long-term co-operation of city development plan stakeholders. This is the way to build future liveable cities.
Over the past few years we have seen dramatic photographs of flooded streets appearing regularly in the media. Meanwhile, prominent scientists are warning that extreme weather will become even more common in the future. This means that the demands on storm water management infrastructure in European cities will be greater than ever before.
Implementation of sustainable storm water management
Sustainable storm water management schemes must be integrated design solutions involving a set of measures suited to specific local conditions. Such an integrated storm water system has not only to consider and manage storm water in present climate conditions, but also all potential future climate change scenarios (e.g. more intense rain events, less rain, rising temperatures etc.). Comprehensive long-term planning for storm water is crucial and should involve integrated designs utilizing various innovative technical solutions, including BGI.
There are three basic recommended stages to be taken when managing storm water in urbanized areas:
- The first step is based on the idea of keeping storm water where it falls and retaining it locally.
- If the amount of water is too great for local retention, then in the second step it is necessary to store storm water in extra storage capacity – either naturally or artificially created.
- Excess storm water that cannot be retained or stored must be, in a third step, slowly drained through available or created waterways.
It is important to consider the design, construction and maintenance costs of BGI. Experience from many European countries suggests that maintenance costs and responsibility for maintenance of SuDS is usually more challenging than the cost of implementing SuDS in new developments. Responsibility for maintenance of SuDS needs to be clearly defined in legislation. However, financial costs of implementation can still present obstacles, particularly when robust legislation requiring SuDS is not in place. Various tools exist for comparing costs, potential benefits and cost savings over the lifetime of projects.
SuDS are sometimes incorrectly viewed as being more expensive than conventional storm water management. This misconception comes from too narrow a focus on investment costs for projects in city centres. On the contrary, they are usually more cost effective than conventional methods, and they also bring additional multiple benefits.
Steps towards Blue-Green Cities
The process of implementing SuDS across all urban areas in Europe has been slow. However, change is still possible if action is taken to improve and increase the use of BGI. Measures should be focused on the documentation and communication of the multiple benefits of SuDS; introducing legislation to support SuDS implementation; establishing a more comprehensive approach to create blue-green infrastructure spatial plans; estimating how the above-mentioned plans can support the mobility in urban areas; and finally, proving the effectiveness and benchmarking of specific SuDS schemes relating to urban mobility.
Recommendations can be summarised in the following way:
- Raise awareness of the multiple benefits of SuDS, in particular those relating to health and well-being, the cost savings of SuDS over the life-time of such projects, and the role of SuDS in supporting the achievement of the UN 2030 Sustainable Development Goals. The support of the public, politicians, decision makers and developers of SuDS is essential. The benefits of SuDS should be used to campaign for stronger and clearer legislation in requiring SuDS in new developments and existing urban areas.
- Establish sustainable and verified design principles. Guidelines and toolkits that support new and innovative approaches, reduce flood risk, increase biodiversity and reduce the costs of water treatment need to be identified. These should also promote master planning, climate change modelling and consideration of local conditions, e.g. rainfall intensity and impact on SuDS from salt used in cold environments. These should be disseminated through a Europe-wide independent industry community hub on sustainable storm water management that shares best practice.
- Planning and co-operation – close and well-timed co-operation, early consideration at the master planning stage to foster creativity, consultation and partnership between city planners, architects, urban drainage engineers, ecologists and landscape architects are key. This co-operation has already resulted in new sustainable storm water master plans, incorporating Blue-Green Infrastructure. Co-operation in incorporating SuDS into urban areas during the urban planning process, can also make alternative mobility options, such as cycling and walking, more attractive than driving, and so alleviate vehicular traffic.
- Local communities and various stakeholders must be involved in the process of planning, design, and implementation of sustainable drainage systems at an early stage. With an effective participation strategy, guidance and public education SuDS can improve community life where people are involved in local activities.
Blue-Green Infrastructure can provide essential benefits to flood management and co-benefits to society and the economy. It can also provide additional benefits such as increased biodiversity, recreational opportunities, and carbon sequestration, which makes for a compelling investment case. With the right water management, we can transform storm water from a threat to an opportunity, contributing to more liveable cities.
About the authors
Vladimír Havlík graduated from the Czech Technical University in Prague in 1976, where he also received his PhD and became an associate professor in hydraulics. He has been working for Sweco Hydroprojekt a.s. (formerly Hydroprojekt) since 1998. His professional activities are focused on the improvement of water infrastructure (feasibility due diligence studies, master plans, the use of hydroinformatics tools for mathematical modelling of water supply systems and sewer networks) in the Czech Republic and elsewhere. He is a member of the International Association for Hydraulic Research (IAHR), the Czech Association for Water, and the Czech Chamber of Chartered Engineers.
Zdeněk Pliska received his master’s degree from the Czech Technical University of Prague in 1994. After working at a sewer system and water supply company, he joined Sweco Hydroprojekt a.s. (formerly Hydroprojekt) in 1995. His professional activities cover the application of hydroinformatics in the area of water management, especially in the field of urban drainage and sewerage systems and water resources. His key qualifications include mathematical modelling, GIS applications and software development, which he uses for his work across the world. He has been a member of the Czech Water Association since 1997.
Bernadette Noake holds a BA in Environmental Management from the University of Manchester. She has more than 10 years’ experience of working on environmental projects, specialising in biodiversity conservation. Bernadette has worked for Sweco Hydroprojekt a.s. in the Czech Republic since 2016, and currently works within the international business department. She is responsible for co-ordinating environmental impact assessments on Sweco Hydroprojekt’s international projects and contributes to other water management projects.