Water hazards like floods, extreme rainfall, and droughts can have detrimental impacts on local communities and their economies. Recovering from these impacts might be very difficult, especially in cities where communities live closely together and systems are interconnected. Luckily, there are many solutions that can help cities build resilience.
Today, cities all over the world are facing water uncertainty and with increasing urbanisation and perceptible climate change, water-related challenges are only going to increase.
Last month, Texas experienced yet another extreme weather-related event, which caused devastating power outages across the state. At the same time, 800 local water systems were disrupted, affecting more than 13 million residents. Texas will continue to face more extreme weather the next decades, shows a report from Texas A&M University.
By 2036, extreme rainfall is expected to be 30-50 per cent more frequent than the 1950-1999 average, causing more flooding — especially in Houston and other Texas cities where abundant impervious surfaces increase rain runoff intensity. The Houston area was hit by six flooding events in five years.
At the same time, the state will face more severe droughts due to higher temperatures and increased variability of rainfall. Adding to this, along some parts of the Texas coastline, the storm surge risk may double by 2050 due to sea level rise and more intense hurricanes.
Learnings from denmark
Like Texas, Denmark has experienced the consequences of a changing climate first-hand. Over the past decade, Denmark has witnessed extreme rain events that have caused flooding and damages to homes as well as infrastructure. Efforts to create more climate resilient cities are well underway in Denmark, and since 2012 Denmarks has inforced a national action plan.
This has further encouraged Danish cities and water utilities to look into smart and cost-efficient ways of managing rainwater and creating resilient and liveable cities through stormwater and cloudburst management. Many of these solutions can be implemented directly by other cities, countries and states too.
Here are 8 ways for Texas cities to become more resilient to water hazards
1. Copenhagen, Denmark: Creating a forest and low ravine for rainwater storage
Remiseparken was a hidden, slightly neglected, green gem in Copenhagen, Denmark located in the middle of a social housing complex known as ‘Urbanplanen’. The renewal of Remiseparken therefore plays an important role in making Urbanplanen a safer and more attractive area as well as functioning as a green, dual-purpose, climate adapted area.
A small forest of 20 different species of alder trees (Elleskoven) in Remiseparken delays water during periods of heavy rainfall. The forest is a new, natural space in the park, and it is designed with a particular focus on climate and biodiversity. Elevated footbridges and plateaus invite park visitors to take a walk or sit and linger. These constructions also make it possible to explore the forest even after it has been flooded by storm water following a heavy rainfall event. Rainwater is also collected in a wadi-like trench that runs along the edge of the park.
Combined, these solutions form a large delay basin with a total capacity of 528,344 gallons. The different plant species in the forest and the wadi contribute to a high degree of biodiversity and resilience, and attract a rich selection of animals, insects and birds. Read more
2. Aarhus, Denmark: Separating rainwater from wastewater on the surface
The Municipality of Aarhus, Denmark has a vision of making the city an even more attractive place to live in through its climate adaptation projects, and the local water utility, Aarhus Vand, works closely together with the municipality to fulfil this vision.
Together, they make rainwater a visible element in the form of rainwater lakes, rainwater beds and rainwater drains. They establish hollows and dams, create entirely new urban spaces and find new ways to lay out green areas. In this way, rainwater is handled in a combination of pipes and surface solutions, using various Nature Based Solution (NBS) elements. The citizens can choose either to handle rainwater on their own plots, or to lead the rainwater to a nearby public area via the surface, where Aarhus Vand handles it. Getting citizens on board on a project such as this is a crucial task. Thanks to a successful citizen involvement process with a combination of workshops, extensive FAQ’s and even individual advisory sessions on private plots, the house owners embrace the new recreational solutions. Read more
3. Odense, Denmark: Simulation of sustainable storm water infiltration strategies
The developed urban hydrology model ‘MODFLOW-LID’ was demonstrated for case areas in the city of Odense, Denmark. Different nature based solution strategies were simulated on detailed scale and upscaled by the model to neighborhood scale. NBS strategies included the use of rainwater tanks, green roofs, raingardens and soakaways on private parcels as well as swale-trench systems with water brakes and overflow to the existing sewer system underneath roads. Special attention was given to the simulation of rainwater harvesting (rain tanks) and green roofs in combination with infiltration devices to manage sustainable infiltration strategies in terms of both maximising the infiltration, minimising the risk of a shallow groundwater table underneath buildings and delaying storm water runoff to the existing sewer system. Read more
4. Jurong region, Singapore: The Lakeside Garden
Once a mangrove swamp, the Jurong region in the South-Western Singapore is being developed into a new business and leisure destination called the Jurong Lake District. The Lakeside Garden is the first phase of the Jurong Lake Gardens, which is the recreational area of the new district.
One of the most visible features of the garden is the ‘Rasau Walk’, which is a winding, barrier-free, waterfront boardwalk along the Jurong Lake shoreline. Other features include grasslands for bird hides, islands for herons and a stream forest, which is a suitable habitat for dragonflies. All fallen trees have been repurposed into site furnishing and landscape features such as bird platforms, habitat logs, pathway curbs or nature trail features – all in order to support and improve biodiversity. There is a nature-inspired play area, which is the largest of its kind in the country. It offers a variety of experiences for children, such as the opportunity to crawl through a ‘squirrel’s nest’ and glide through a tree canopy. Jurong Lake Gardens is a park where people, animals and plants can co-exist and mutually benefit. Read more
5. Nye, Denmark: a new, sustainable and water-wise suburb
The vision of Nye, Denmark is to create a water-wise, urban district, where it will be effortless for citizens to live sustainably. Blue/green structures will promote biodiversity in this new suburb, which is developed to manage predicted climate change.
Rainwater is harvested and treated locally for re-use in households, hereby preserving groundwater resources. Rainwater from roofs, roads and recreational areas is collected in open trenches and runs to small rainwater basins, before ending in the largest basin. This creates an attractive open, lakeside space. From the large lake, water is channelled into a treatment plant, where it undergoes a three-step treatment process before being distributed to the area’s homes in a separate pipe network.
The first phase of the project includes up to 650 households, where permit is given by authorities to use treated rainwater for toilet flushing and laundry. Meter data from the first 50 households shows that non-potable water use covers around 40 per cent of the total water use, confirming the expected level. Nye demonstrates a new and sustainable way of including rainwater into household use – a holistic approach to rainwater management in an urban area. Read more
6. Gladsaxe, Denmark: Sports center uses climate adaption as stepping stone for new recreational facilities
Extreme rain events have caused flooding on several occasions in the Copenhagen suburb of Gladsaxe. To prevent future flooding, a large climate adaptation project was completed at Gladsaxe Sports Centre.
The sports centre is situated on top of a large regional water system. By diverting rainwater through a series of ponds and canals, additional capacity was created in the sewerage systems both locally and in the low-lying areas between Gladsaxe and the sea. By choosing surface solutions with dual purposes rather than traditional underground reservoirs, the project saved approx. $ 4,762,360.00, proving it to be a very cost-efficient solution. Keeping the rainwater above surface also became a stepping stone for creating new recreational areas and playgrounds.
Eight different holes were constructed to function as different recreational areas when they are not used for collecting rainwater. For sports enthusiasts, the park has been turned into a concrete corridor for skateboarders and a paddle tennis field. As the holes have a more informal setting, the park now has a much wider appeal for the overall local community, who utilise the park for activities such as jogging, playing, dog walking and taking Sunday strolls. Read more
7. Kampung, Singapore: Hydrological building design promotes both social and environmental sustainability
To accommodate the need for public housing in Singapore, an empty lot was transformed into what is now Kampung Admiralty. The uniqueness of Kampung Admiralty stems from its design, which focuses on both social and environmental sustainability. It encourages the elderly residents to engage in an active lifestyle among younger generations, but it is also part of a greater effort to increase environmental sustainability.
The hydrological design of the building allows nearly 1,056,688 gallons of water a year to be harvested, stored and reused for irrigation. The rainwater travels through a large series of gardens, which function as a vegetative storm water filter.
Furthermore, an eco-pond improves biodiversity and provides a cooling effect in an otherwise warm, urban climate. With its ambitious amounts of greenery, Kampung Admiralty stands out in a densely populated urban area. It is a prime example of how climate adaptation thinking can be used to lessen the impacts of increasing urbanisation. Read more
8. Greve and Solroed, Denmark: Cost-efficient climate adaptation and wetland restoration
Heavy rainfalls used to lead to severe flooding in the Copenhagen suburbs Greve and Solroed. Today, the increased volume of rainfall is used positively in a restored river valley with an open pond and wetlands, which provide both recreational value to the citizens and improved habitats for flora and fauna.
A new pond purifies rainwater before it runs to the re-established river, allowing trout and other wild fauna better living conditions. At the same time, the water utility now has access to 8,000 gallons of rainwater storage during storm water events.
The Karlstrup Marsh project is a unique collaboration between KLAR Utility and the two municipalities of Greve and Solroed and has created win-win solutions for everyone involved, including local sports clubs, farmers and bird watchers. In Karlstrup Marsh, climate change adaptation became a strong driver of sustainable and cost-efficient development as the project saved the water utility company construction costs for traditional urban retention basins. The holistic approach had a strong focus on stakeholder involvement, alternative financing mechanisms and not least technical solutions involving a new stream established through the local forest. Read more
Read the brand new white paper Nature Based Solutions for more solutions on how to use rainwater as a resource to create resilient and liveable cities.