In built-up urban areas, trees can help restore pre-development water flows and remove pollutants and filter water. Trees act as natural filtration machines, which can hold, release, and clean water through soil and evaporation.

A question often asked regarding urban trees and water capture is, can stormwater runoff from roads be too polluted for the trees to use?

Yes, stormwater can be very polluted, as large amounts of debris, particulates, and rubbish can suffocate a tree and prevent water and nutrients from reaching the tree’s root system for absorption.

Gross pollutants, such as plastic rubbish or vehicle parts, can largely be filtered out often by screens, like stormwater grates.

Smaller than gross pollutants are total suspended solids (TSS). TSS refers to solids suspended in water or wastewater that can be trapped by a filter. TSS can include various materials, such as silt, decaying plant and animal matter, industrial wastes, and sewage. High suspended solids concentrations can cause many problems for stream health and aquatic life.

Then there are soluble or water-borne pollutants, which are difficult to filter out economically. These pollutants can cause severe damage to ecosystems.

Storm water systems can be installed, which prevent these pollutants from accumulating in our water streams. Citygreen offers a revolutionary range of stormwater management solutions that prevent water pollution and make it easier –and more affordable–to manage and re-use stormwater.

Why use Trees for Stormwater Management?

Trees offer a large value add when compared to traditional stormwater management systems. Trees for stormwater management offers numerous advantages in urban areas. Firstly, trees act as natural water managers by absorbing excess rainwater, mitigating the risk of flooding and erosion. Their extensive root systems serve as filters, trapping and breaking down pollutants present in stormwater, which ultimately improves the quality of water entering local water bodies. Additionally, trees reduce the volume of stormwater runoff, easing the burden on municipal drainage systems. Moreover, these green giants contribute to urban cooling by providing shade and releasing moisture through transpiration, enhancing the overall urban microclimate and conserving water by reducing evaporation from impermeable surfaces.

Case Study: Urban Trees for Shade & Stormwater Management at Kinsmen Sports Centre in Edmonton

Furthermore, the aesthetic and social benefits of urban trees are noteworthy. Well-maintained green spaces with trees enhance the quality of life for urban residents and promote community well-being. Trees also create habitats for wildlife, contributing to urban biodiversity and ecological balance.

Engaging communities in tree planting and maintenance fosters a sense of ownership and responsibility. From an economic perspective, effective stormwater management with trees can lead to cost savings by reducing the need for extensive stormwater infrastructure. Lastly, utilizing trees that align with regulatory compliance, as many cities and regions have specific stormwater management requirements where integrating trees into stormwater management strategies not only addresses practical concerns but also contributes to the creation of attractive, sustainable, and resilient urban environments.

How Do Trees Clean Stormwater?

Trees play a vital role in filtering water through a series of natural mechanisms. Their root systems, for instance, engage in a process called root uptake, where they absorb water from the soil, including groundwater and rainwater. This not only helps in managing excess water in urban areas, reducing the risk of flooding and waterlogging, but also contributes to water purification. As water moves through the soil surrounding tree roots, it undergoes natural filtration. The soil acts as a powerful filter, capturing impurities, sediments, and pollutants present in the water, thereby improving water quality. Microorganisms in the soil and on tree roots further aid in this process by breaking down organic matter and pollutants into less harmful substances.

Additionally, trees are proficient at nutrient uptake, extracting essential nutrients from water for their growth. In doing so, trees indirectly remove excess nutrients like nitrogen and phosphorus, common water pollutants. Some tree species excel at phytoremediation, absorbing and storing pollutants such as heavy metals and chemicals, thus contributing to water purification and helping prevent water pollution.

Trees release water vapor through transpiration into the atmosphere, mitigating local flooding risks by reducing runoff volume. Trees also help retain sediments and prevent erosion, which can lead to waterbody sedimentation and, consequently, improved water clarity. Altogether, trees collectively enhance water quality by naturally reducing contaminant levels, pollutants, and sediments, making a significant positive impact on the health of water systems.

Case Study: Pelican Waters

Pelican Waters, a residential estate located on the Sunshine Coast of Queensland, Australia, has been trialling Citygreen’s Strataflow™ system with so far great success.

This new development aimed to use the advanced water-sensitive urban design (WSUD) and improve sales of lots near bioretention basin. Research has shown that preserving natural features in residential developments can increase the value and sale price of lots.

Instead of a traditional bioretention basin, Citygreen’s Strataflow™ uses an underground structural soil cell system, which delivers a high standard of stormwater treatment with a completely natural look.

To any passer-by, what you see is a healthy, flourishing tree, surrounded by a grassy verge, but beneath the ground is an advanced WSUD.

The Strataflow™ is a specialised design ‘hybrid’ tree pit, combining the best urban forestry for sustained and healthy tree growth with fully functional stormwater management – including filtration and flow management.

These designs may start with the Strataflow Kerb Inlet. This device sits in the road kerb alignment, retaining the inherent structure of the concrete kerb. The inlet has a grate (acting as a screen), to stop larger-sized pollutants from entering the system, which inhibits healthy tree growth.

The inlet lets water from the road carriageway flow through the front grate of the drain at a capacity of up to 18 litres/ 5 gallons per second. This allows the inlet to minimise pollutants entering waterways and reduce flood risks by controlling the stormwater flow entering our city’s underground drains.

When the water flows through the street, it enters through the inlet and flows underground. From there, the stormwater reaches the stratavault system, where the stormwater is stored, filtered and distributed effectively for the benefit of urban trees and for proper stormwater management.

The inlet ensures the water drains down at the correct optimal depth beneath the pavement height. From there, the stormwater reaches the structural soil cell system and the trees’ root system, where the stormwater is stored, filtered and distributed effectively for the benefit of urban trees and for proper stormwater management.

Essentially, Strataflow™ utilises readily available stormwater rather than potable water to irrigate street trees, which improves the vitality of trees and reduces the impact of stormwater on the local environment, all while maintaining a high natural presentation.

Green space for shading and mitigation of heat island effect

Soil Used for Stormwater Filtration

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Looking for a cost-effective and sustainable stormwater solution? Contact our friendly Citygreen Team now by clicking here.

Australia’s island state, Hobart, is well known for its history of catastrophic fires, including the disastrous wildfires of 1897-98 and 1967. As the second-driest city in Australia, it’s easy to forget though that Hobart is also vulnerable to serious flooding. Until earlier this month that is, when a record 236.2mm of rain fell on Mount Wellington and 129.2mm fell in Hobart. The deluge flooded the city, with the Hobart Rivulet breaking its banks and flooding other lower lying areas in Sandy Bay, South Hobart, New Town, Lenah Valley and Kingston. In Hobart, cars were swept away in Collins St and Syme St and McRobies Rd in South Hobart.

Hobart’s closeness to nature and surrounding hilly terrain makes the city especially prone to wildfire and flash-flooding. But, the May 2018 flooding is also partly attributable to the city’s postwar planning. Like the rest of Australia, city planning in Hobart was dominated by, “a disconnection from nature. Creeks and streams were filled in, built over or walled off (taming nature), creating risks of catastrophic failure in unexpected conditions. This approach also overlooked the important ecological functions of watercourses.”

Unfortunately, the problem is only getting worst as Hobart expands, with houses, roads and buildings increasing the hardscaped area and decreasing green cover, which acts like a sponge. Planners now must apply water-sensitive urban design principles, including protecting floodplains from development, limiting the development of very steep land, and restricting land uses on flood-prone sites. Separately, thought must be given to the development of the urban forest – planting urban trees and carefully incorporating water sensitive urban design to better manage stormwater runoff. Good planning can help prevent future disasters and keep Hobart’s residents out of harm’s way.

Source: https://theconversation.com/lessons-in-resilience-what-city-planners-can-learn-from-hobarts-floods-96529

Citygreen at the 2015 NSW/WSUD/IECA Conference:

With our ongoing support of the stormwater industry, Citygreen® is proud to announce it’s involvement in this year’s NSW/WSUD/IECA Conference, on the 19th-23rd of October at Dockside Darling Harbour, NSW.

For more information please visit: www.wsud2015.org

With increasing urbanization, and more highly concentrated populations within cities, strengthening the green infrastructure is becoming increasingly important. One of the largest opportunities for impact is maintaining and enhancing the urban canopy. This is addressed most readily by advanced tree pit design, which refers to the subterranean structures put in place during planting.

In Minneapolis, the local government conducted research that revealed well-planted trees provide a strong financial incentive in addition to the ecosystem benefits. The research found a $2 million savings between a storm water conveyance system, or subterranean cell systems.

Peter MacDonagh, a landscape architect, said in an ASLA interview, “larger, older trees are far more valuable than younger ones, so work needs to be done to preserve these and use new techniques to enable younger trees to stay in place longer.”

As trees were planted in the past, the soil they were placed in was compacted, causing a lack of nutrients, storm water management, and root establishment. As a result, the trees struggle to thrive and provide their benefits to the local environment and infrastructure. Often, these struggling trees will either die, stop growing, or begin to push through and ruin sidewalks and roads.

“The Center for Urban Forest Research calculates that large-canopy trees …outperform small trees…and they do not start adding significant environmental performance until they reach 30 feet,” states Matthew Gordy, a landscape and urban design professional.

By utilizing cell systems, the strain put on the trees’ growth is almost completely eliminated, resulting in lower costs, and increased shade, stormwater management, and overall well being of the populaces and local infrastructure.

Get more information on advanced soil cell systems here.

Tree Pit Opening

The Future of Urban Water:

What would the state of urban water be in the next couple of years?

Well, the report The Future of Urban Water: Scenarios for Urban Water Utilities in 2040 by ARUP explores trends and future scenarios for the future of urban water utilities in 2040. It is the result of a jointly funded collaboration between Arup and Sydney Water.

“The programme has helped us gain a better understanding of possible pathways into the future, including implications for future infrastructure, governance and customer experiences.”

It depicts four plausible scenarios for the future of urban water utilities in 2040, using Sydney as a reference city. The report explores how a wide range of social, technological, economic, environmental and political trends could shape the urban water future.

The World Economic Forum’s Global Risks 2014 report said water crises is one of the top five global risks posing the highest concern. “Despite this, water issues are often overlooked or misunderstood, and there is a need for better awareness of their social, economic and environmental impacts.”

The Arup report said aside from the increasing water scarcity and pollution, rapid population growth and urbanisation are “major factors posing fundamental challenges to the global water cycle, with a particular pressure on the urban water supply”.

Australia utilises over 50 percent of its water consumption for agricultural purposes. The rest is for household, industrial and commercial use. But in urban areas, “the main driver for demand remains the population, and thus population growth”.

One of the key drivers for water conservation is smart infrastructure. It responds intelligently to changes in its environment to improve performance. “It is estimated that the market size for smart grid technologies will almost triple by 2030. Smart water networks could save the industry US$12.5 billion a year.”

Another is the change to a more digital lifestyle where people will be able to monitor the consumption and cost of water in real time. “More awareness of the issues could lead to increased scrutiny of water utilities and pricing of services. The availability of data provides an opportunity to educate customers about consumption and managing resource use.”

The report also mentioned new solutions for water supply such as the extensive use of desalination. About 96 percent of the earth’s total water supply is found in oceans. “Worldwide, desalination plants are producing over 32 million cubic metres of fresh water per day. However, energy costs are currently the principal barrier to its greater use.”

Finally, the report also said green infrastructure is part of the plan. “Benefits of increased green infrastructure include the reduction of flood risk, improved health and wellbeing as well as providing a habitat for wildlife. Extensive green networks can be formed over time to create an encompassing city ecosystem that can support the sustainable movement of people, rebuild biodiversity and provide substantial climate change adaptation.”

For more of the report, you can check this out.

As urbanization continues to reshape our landscapes, the concept of a Water Sensitive Urban Design (WSUD) has gained prominence as a holistic approach to address the challenges of water management in cities. Let’s look into the intricacies of WSUD, examining its principles, benefits, challenges, and implementation strategies.

Water Sensitive Urban Design (WSUD) is also known as Low Impact Development (LID) in the United States, and Sustainable Urban Drainage Systems (SUDS) in the United Kingdom.

It all refers to the land planning and engineering design approach that integrates the urban water cycle, including stormwater, groundwater, and wastewater management and water supply, into urban design. This is done to minimise the environmental degradation as well as improve the look of the area by creating a circular economy of urban water use.

In urban environments, impermeable surfaces like roads, roofs, driveways, and walkways prevent water from soaking into the ground, resulting in what we call stormwater runoff. Additionally, the presence of vehicles and industrial activities in these areas contributes to the accumulation of pollutants on these surfaces. When it rains, this polluted runoff is funneled through drains, eventually reaching creeks and rivers, causing pollution and degradation to environmentally crucial systems. Water-Sensitive Urban Design (WSUD) is a solution designed to enhance urban areas’ capacity to capture, treat, and recycle stormwater, preventing it from polluting and harming our natural waterways and ensuring rain water is used in the environment in which is falls more efficiently.

Why Use Water Sensitive Urban Design When Designing your Urban Environment?

According to the guidelines released by the South Eastern Councils in Melbourne Victoria, WSUD has been identified as a “means to control flows and filter stormwater to remove pollutants”.

Stormwater is the water that runs off urban surfaces after heavy rainfall. The report said it has been identified as the key cause of pollution and declining health of waterways.

“With increased urban development, the proportion of impervious surfaces in our catchments increases. This increases the velocity and amount of water running into our waterways, creating problems of erosion and flooding and changing natural flow regimes, with associated ecological damage. It also washes more pollutants into our streams, further impacting river health.”

Victoria councils, like other councils in Australia, have recognised the importance of sustainable water management such as WSUD. The release of various guidelines enables organisations to have a first point of reference for their projects.

The design “integrates urban water cycle management with urban planning and design, with the aim of mimicking natural systems to minimise negative impacts on the natural water cycle and receiving waterways and bays”.

Types of WSUD

Soft vs Hard Engineering of Landscapes

Soft engineering and hard engineering are two approaches used in water management and urban design.

• Soft Engineering: In the context of Water Sensitive Urban Design (WSUD), soft engineering refers to the use of natural or nature-based solutions to manage water, such as vegetation, soil, and natural drainage systems. Soft engineering aims to mimic natural processes and ecosystems to reduce runoff, improve water quality, and enhance the aesthetic and ecological value of the landscape. Examples of soft engineering in WSUD include bioretention swales, vegetated basins, soil cell tree pits, and constructed wetlands.
• Hard Engineering: Hard engineering, on the other hand, involves the use of man-made or engineered structures to manage water, such as pipes, concrete channels, and traditional drainage systems. In the context of WSUD, hard engineering components may be necessary in situations where factors such as the need to transport water across paved areas, land availability, or topography require the use of piped or hard components. Examples of hard engineering in WSUD include piped drainage systems, concrete structures, and permeable hard surfaces such as rock rip-rap or paving.

WSUD elements are most effective when vegetation and trees are used in their design, factors such as the need for water to be transported across paved areas, land availability, and topography may require the incorporation of hard components into a broader WSUD system.

While there is no standard approach that should be applied to all situations, and a hybrid solution that combines both soft and hard engineering components may be necessary to address site-specific opportunities and constraints, Creating softscapes with increased greenery and trees will be a great economic, environmental and health impact to the local community.

Case Study

In places such as Canada, capturing stormwater is a mandatory requirement for all new constructions, as a means to effectively manage water and prevent a higher level of pollutants from entering municipalities.

In flat open areas such as carpark where pollutants and stormwater runoff can be a concern Citygreen’s Stratavault offers a cohesive solution that connects stormwater management with landscape tree design. Instead of stormwater immediately entering the city infrastructure and depleting the valuable water resource by taking it out of area, our integrated water sensitive urban design directs the stormwater into the Stratavault matrix.

This innovative system allows trees and soil to utilize the water for their own needs and growth while effectively cleaning the excess water of contaminants before the water enters the pit’s base chamber. Additionally, this design enables the recycling of water for on-site irrigation & a slower release back into the city’s infrastructure during periods of lower demand

What are the Key Principles of WSUD?

Some of the key principles of WSUD as stated in the Urban Stormwater: Best Practice Environmental Management Guidelines (BPEMG) include:

• Protect and enhance natural water systems within urban environments.
• Integrate stormwater treatment into the landscape, maximizing the visual and recreational amenity of developments.
• Improve the quality of water draining from urban developments into receiving catchment environments.
• Reduce runoff and peak flows from urban developments by increasing local detention times and minimising impervious areas.
• Minimise drainage infrastructure costs of development due to reduced runoff and peak flows.

What are the Benefits of WSUD?

The top benefits of using water sensitive urban design include:

1. Flood Mitigation: By reducing stormwater runoff and increasing water infiltration, WSUD minimizes the risk of flooding during heavy rain events.
2. Improved Water Quality: Natural filtration methods used in WSUD systems effectively remove pollutants, enhancing the quality of water entering streams and rivers.
3. Urban Cooling: Urban green spaces and water features provide cooling effects, mitigating the urban heat island effect and improving overall urban livability.
4. Biodiversity Enhancement: WSUD encourages the creation of habitats for various species, contributing to urban biodiversity and ecosystem health.
5. Enhanced Tree Growth: By directing extra resources to nearby trees you give the tree more opportunity to successfully grow
6. Increased Social Outcomes: Improving the greenery, liveability, and functionality of shared urban spaces increases the the physical, social and mental health of the community.

What are the Challenges of WSUD?

Given that water-sensitive urban design is a relatively new concept within the realm of urban landscaping, there emerge several challenges in the process of designing new WSUD spaces. These include:

1. Regulatory Barriers: Traditional regulations and codes may not be aligned with WSUD principles. Overcoming regulatory hurdles and advocating for changes to local ordinances can be a significant challenge.
2. Lack of Awareness: Many stakeholders, including local governments, developers, and the general public, may be unaware of the benefits and importance of WSUD.
3. Funding Constraints: WSUD projects may require upfront investments for designing, construction, and maintenance. Convincing stakeholders to allocate budgets for these projects in the face of other competing priorities can be challenging.
4. Infrastructure Retrofitting: Integrating WSUD into existing urban areas often requires retrofitting existing infrastructure. This can be complex, costly, and disruptive to ongoing operations.
5. Maintenance and Long-Term Management: Proper maintenance of WSUD components is essential to their effectiveness. Ensuring consistent and appropriate maintenance practices can be challenging, especially if communities lack the necessary resources or knowledge.
6. Data Availability: Designing WSUD systems requires accurate and up-to-date data on rainfall patterns, land use, and hydrology. In some cases, obtaining this data may be a challenge, especially in areas with limited resources for data collection.
7. Interdisciplinary Collaboration: WSUD projects require collaboration among various disciplines, such as urban planning, landscape architecture, civil engineering, and environmental science. Coordinating and aligning efforts across these disciplines can be complex.
8. Resilience to Climate Change: WSUD systems must be designed to accommodate changing climate patterns, including more frequent and intense rainfall events. Ensuring the resilience of these systems can be a challenge.

Rainwater Runoff

Citygreen® products are designed to ensure it supports the effort for a sustainable water management. The Stratavault’s™ modules leave over 94 percent of its total volume for root growth and storm water harvesting. Find out more about the products here.