Why An Integrated Approach to Urban Water Management is Key to the Future of Our Cities

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Introduction

Water has always been a staff of life, and sometimes the carrier of death! Water management in cities, including the provision of drinking water and removal of waste water, appear to have been a challenge for engineers since ancient times. The earliest urban water systems, which transported human and animal waste water outside of the city to irrigate fields and used aqueducts to bring in drinking water can be found in ancient cities such as Rome and Constantinople (Istanbul) among others. Modern day sewage systems with pipes, pumps, sand filtration and chlorination only emerged during 18th century London, England. News of the discovery of the link between cholera and contaminated water from the Thames River ignited policy efforts to improve drinking water quality and separate wastewater and drinking water systems. 

The urban heat island effect is the result of too many impervious surfaces that heat up and cause temperature to go up, making cities more and more uninhabitable.

Incredible public health successes were achieved this past century, largely due to improved drinking water and wastewater management. Water-borne diseases have all been wiped out in most of the developed world. Yet, as cities have grown and grown, new water challenges have emerged. Traditional development practices in North America have and continue to generate hundreds of square miles of impervious surfaces - roofs, pavement, parking lots and roads. Rainfall, and snow melt in some cities, results in stormwater, which rather than infiltrating into the ground, runs off impervious surfaces, often in large volumes which can scour streams, killing aquatic life and even cause drownings. Furthermore, all of these impervious surfaces contribute to the urban heat island effect. The heat of the sun strikes these surfaces which then heat up the surrounding air. This causes urban and suburban areas to be significantly hotter than the surrounding countryside, resulting in negative health impacts, a rise in heat related mortality and much greater overall energy use for air conditioning. 

Integrated stormwater management projects helped Copenhagen restore swimming to its harbour waters. Photo: Steven Peck

Now climate change is a real game changer because it impacts both gray and green infrastructure. It contributes to new stormwater challenges by increasing the intensity and frequency of severe weather events. Intense storms expected once in one hundred years are occurring much more frequently, causing flash flooding and a threat to property and human life and multi-billion dollar insurance claims. The American Society of Civil Engineers’ “2021 Infrastructure Report Card” reports nine billion dollars in annual flooding damages, and the impervious surfaces of sprawling cities continue to grow. 

In addition to the threat of flooding, stormwater is also terribly polluted. In older cities, stormwater and wastewater may often combine during storms, resulting in diluted sewage by-passing treatment plants and flowing through to our rivers and streams. In general, stormwater undermines the health of our streams, lakes, and estuaries making the water undrinkable, unswimmable and unfishable. This is because contaminants, such as oil, grease, metals, dog feces and pesticides, tend to build up on urbanized surfaces. These contaminants come from sources such as pavement deterioration, tire and brake-pad wear, vehicle emissions and spills as well as yard and garden care, and pets. Stormwater runoff picks up these contaminants and transfers them to streams, lakes, estuaries and even groundwater. In the US, it is estimated that nearly 600,000 miles of rivers and streams and more than 13 million acres of lakes, reservoirs, and ponds are considered impaired due to stormwater runoff. 

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Stormwater management policy in European and North American cities lags behind wastewater and drinking water management. In the US, more than 40 states now have some form of stormwater utility whose job is to better manage stormwater, through regulations and the monetization of stormwater runoff, so that it is no longer bundled with drinking water or wastewater charges. See Shanyn Viars article on tradeable stormwater credits. 

Unmown bioswales in Copenhagen retain and inflatrate more water and support biodiversity. Steven Peck

New Approaches Needed

Climate change, with its multiple challenges of drought, flood and extreme heat, requires that we change how we manage stormwater in our cities. We need to adapt rapidly, or continue to suffer from the many negative impacts of extreme weather. This means looking at stormwater as a resource, to capture and use, rather than as something we must pipe and move away from building sites as fast as possible. It means using a combination of grey and green infrastructure in a treatment train approach, starting at the roof, and moving down to the walls to the landscapes, streetscapes, parks and beyond, to retain, detain, reuse and cleanse stormwater. It also means selecting plants that have the ability to withstand more heat and drought conditions. Bruce Dvorak has written an excellent article on climate change resistant plants. 

The use of green infrastructure investment through the State Revolving Fund Program in the US is increasing. Source: Clean Water SRF Program Information National Summary (2019)

Green infrastructure investment is on the rise in the US and Canada, but we still have a long way to go to establish a supportive regulatory and professional interdisciplinary cooperation required to design and implement climate adapted neighborhoods, to reduce the urban heat island and have the capacity to reduce flooding during intense storms. Civil Engineer Nicole Holmes describes some of the current challenges with the traditional stormwater development process associated with securing green roofs on projects. She explains that all too often experts make important decisions about the development in isolation from other disciplines, preventing more effective and less costly stormwater management solutions. In her article, Dr. Karen Liu provides us with a case study of how to meet stormwater objectives and save money on storage systems simply by modifying a green roof design to achieve water balance. There are many tools in the tool box to improve design and overall performance of green and grey infrastructure. 

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Open ponds in Augustenborg, Sweden are part of the climate adaptation treatment train designed to handle the next 100 year storm without property flooding. Photo: Steven Peck

Read this case study on the new Harvard Engineering building illustrates the benefits of a more integrated stormwater management approach. The project uses a very clever system of green roof terraces in a treatment train approach, and then captures excess stormwater for reuse in the building. Helen Johansson from the Scandinavian Green Roof Institute describes integrated stormwater management (climate adapted) projects implemented in Augustenborg, Sweden. 

These innovative development projects use an integrated design approach to stormwater management, and employ hydrological models that examine stormwater retention and detention potential of multiple roofs, as well as bioswales, parks and school yards, designed to detain large volumes of stormwater, sometimes by temporarily flooding to avoid flooding nearby buildings. Water detention and storage can also be used to irrigate roofs and landscape during drier months, saving potable water, while allowing plants to do their important job of cooling our buildings and communities. These projects are a win-win-win situation, but they require regulatory flexibility, the acceptance of risk, and cooperation among the participants – the private building owners and the city officials, says Herbert Dreiseitl. Herbert is an award-winning artist, architect, planner and designer who has over 40 years pioneered new methods and approaches to stormwater management that even go further. He sees integrated water management in urban areas as an opportunity to engage community, and provide multi-functional art and amenity spaces, in addition to keeping basements dry. See Sustainable Futures Podcast featuring Herbert as a guest. This approach recognizes the importance of community, and of creating high quality and healthy environments to sustain urban dwellers. His projects include Potsdamer Platz in Berlin and Tanner Springs Park in Portland, Oregon. 

Copenhagen, which has endured several major floods in the past 20 years, has been redesigning its stormwater management and green spaces to prepare for the next onslaught. Professor Leila Tolderlund provides a beautiful case study of one such project I was fortunate to visit this summer after attending the World Green Infrastructure Congress in Berlin. This multifaceted stormwater management project allows for evaporation and infiltration along a vegetated linear park that moves through several neighborhoods and eventually leads to the harbor, where recreational swimming is not only allowed but encouraged. 

Tanner Springs Park in Portland, Oregon is a multi-use park that employs multiple features to manage stormwater in the area, while providing high quality art and amenity spaces. Photo: Herbert Dreiseitl. 

Conclusion

We’ve come a long way since the days of widespread cholera outbreaks from drinking contaminated water in our cities. The new challenges resulting from ongoing city expansion and climate change will require that we learn to adapt our development approaches much faster. The old approach is no longer serving our needs. 

Fortunately, new approaches are gaining a foothold. They all begin by seeing stormwater as a multi-faceted resource that can support much needed plant growth to cool our cities, reduce flooding, improve human health, grow food, support biodiversity and even be inspired through water-based public art. The integrated design and redevelopment of our city surfaces is key to preparing for the next big storm that climate change throws at us, and the very maintenance of city life. 

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Steven W. Peck, GRP, is the Founder and President of Green Roofs for Healthy Cities; Co-Founder World Green Infrastructure Network and the editor of the Living Architecture Monitor magazine. He can be reached at: speck@greenroofs.org. 

Source: Clean Water SRF Program Information National Summary (2019)