A Case of the Sweats: an argument to address the urban heat island effect


For this blog I would like to discuss and present a case for the need for the heat island effect to be addressed. So firstly how exactly does the #urbanheatislandeffect (UHI) work and why should we even consider being concerned? Watch this video below to get an idea of the UHI, with the example of Western Sydney:

So this concept has actually been around for a while now but I believe that considering how much we know and have researched and studied into this field it is surprising the lack of actual change has occurred. So for this blog I will:

  • Discuss the implications of UHI effect for the future
  • Present the strategies we have now to address it and what are the benefits 
  • Consider what barriers need to be overcome to address the issue
  • Use the principles of #ecologicalengineering to suggest a way forward

Implications of the UHI effect

Diagram from here

“If you can’t stand the heat, get out of the kitchen.”

Harry S. Truman

The only problem of course with this quote is the implication that if we can’t handle the pressure we should leave it for someone else; a classic way to neglect future generations, an attitude that I think we need to squeeze out of society.

A recent study (only one of many examples) in Hong Kong showed that the city had a rise in urban mean temperature of 0.169 degrees centigrade per decade for the last four decades. Even here in Australia it has been found by the Melbourne City Council that the average temperatures within the CBD are up to 4 degrees higher than surrounding suburbs.

This phenomenon can be clearly seen as an issue when combined with one of the worlds deadliest natural disasters, in fact this disaster can be held responsible for up to 70, 000 deaths in Europe during the 2003 episode. This natural disaster is known as a #heatwave.

heat wave.jpg
Image taken from an article about scientists being able to better predict heat waves in the future

The pre-existing UHI effect means that cities are more vulnerable to heat waves than surrounding rural areas. Why is this exactly?

So the UHI effect is a localised phenomenon, it creates a permanent temperature anomaly, spatially concentrated. Read this excellent study which looks into the physics details about how this effect works. Whereas heat waves are more large scale, temporal high pressure systems producing an anomaly increasing the air temperature for rural and urban regions. We do have some idea of how the interactions between these effects can lead to intensified heat. Also read section two of this paper to get a better idea of how urban environments impact the balance of energy.

Breaking the problem down further there are two main reasons I believe are sufficient enough to catalyse a movement to deal with the  increased heat in urban areas. These refer to our base case, the “business as usual” scenario:

  1. We know that 50% of the worlds population lives in cities and this is widely known to be increasing, by 2050 it is expected that 66% of the worlds population will be living in cities
  2. We also know that climate change will result in an increase in frequency and severity of heat wave events
  3. We know that heat waves cause more deaths than floods, hurricanes and tornadoes combined. 

The image below highlights the changes that we have already been able to quantify in Australia. In Melbourne, 2013 there was approximately 200 heat related deaths and the predictions are for this to double by 2030. It is a well known fact that, even in Australia, the more vulnerable (the elderly, people with pre-existing medical conditions and the poor) suffer the most from extreme weather conditions. Globally this is also the case, often poorer countries are located in the tropics and Nicolas Herold, a fellow at the Climate Change Research Centre at the University of New South Wales said that he and his fellow researches found that the increase in extreme heat measurements has been more pronounced in poorer countries:

“We expected it to be a lot worse since the [low-income] countries are near the equator but the difference of more than double is quite shocking”.

business as usual

There are other consequences of increasing UHI effect combined with heat waves, I found highlighted nicely in an article I read, that I also think should be considered:

  • The increase in energy consumption and chemicals released by cooling equipment
  • In some places, the increase in power outages
  • Higher concentrations of air pollutants
  • Promotes the creation of ground level ozone which has been known to lead to health issues and intensify numerous breathing problems
  • Higher temperatures of storm water (due to the heating of urban surfaces) which reduces the amount of dissolved oxygen in the water of nearby bodies

What we can do and the benefits

There has been extensive research into methods of combating the UHI effect in order to reduce the severity of the impact of heat wave events on the urban environment. I would like to break them down into 3 areas, one of which I will discuss. The second is to change the colour scheme of our built environments, as is being done in Western Sydney (image below, read here for more on this project and here  and here for more on decreasing albedo).  The third is the modification, planning and the design of cities to increase air flow, an interesting case I found of this is in Stuttgart in Germany, which you can read about here.

Urban heat island effectWestern Sydney’s project for paler roads, watch the video on their website for more.


From an article on the rise of the forest city, with more and more vertical forest towers being created, with the benefits if reducing heating and cooling needs, increasing biodiversity, improving air and noise pollution as well as decreasing the UHI effect.

I read an exciting study published this year, the results of which suggests that:

“…tree dominated greenspace offers the greatest heat stress release when it is most needed.”

A study (discussed in the previously mentioned article) conducted of Glasgow predicted that an increase of 20% in greenspace could eliminated between a third and a half of the cities expected UHI effect in 2050!

In many European cities there has been a push towards rooftop gardens. There are also other creative solutions such as greenscaping into vertical gardens such as in the image to the left, in places such as Bangalore and Beijing.

Just having a surface covered shade can reduce its surface temperature by 11-25 degrees but I think that the most impressive part about greenspaces as a mitigation technique for UHI is the broad range of benefits associated:

  • Other ecosystem services  – reduced surface runoff and modification of micro climates
  • Increased biodiversity
  • Aesthetically pleasing
  • Reduction in energy costs (shading from trees means nearby buildings require less cooling)
  • Improve air quality
  • Storm water management and improve water quality
  • Can reduce noise
  • Decrease stress on water resources

It is quite exciting to think about all of the positives to come out of one relatively small change, which I think will also improve the #livability of our cities, something that seems to be particularly a cultural movement in Australia, to aim for enhanced “livability”.

Who is involved

This is a business case though so I must also address stakeholders and the economic side, as I have clearly highlighted many environmental and indeed ecological benefits. The wider community clearly has much to benefit from a solution like this, not only does it make our neighbourhoods more aesthetically pleasing but also as I have mentioned earlier the health benefits are measurable when it comes time for heat waves. The reduction in energy consumption within buildings introduces big company owners or government agencies who are spending the money to keep their buildings cool. On a wider scale I think it is also important to include future generations as stakeholders as by following “business as usual” current generations are leaving the more severe consequences to be dealt with in the future. I think that local, state and federal government also have parts to play with different levels of the problem. On a grander scale the Federal government have an environmental responsibility (also a global responsibility) and on a local scale the other benefits such as the reduction in noise, for example, are the kind of issues that should be considered anyway.

Arguably it is a good option economically as well. A 5-city study conducted in the US found that when quantified, the benefits of the planting the extra trees amounted to $1.50-$3 per dollar invested!

Something from me

I believe that the way forward isn’t necessarily only to use these methods, I think we are still at the stage where we can consider alternatives that may also assist in mitigating the UHI effect, though clearly greenspacing is such an elegant solution. To come up with these alternative solutions, we should be considering the design principles for ecological engineering (please see my first blog post to be more familiar with these).

I would like to point out the the second principles, design for site specific context,  this I think highlights the limitations with the use of greenspaces. In Australia water is more of a limiting resource in comparison to Europe, where vertical forests have the ability to flourish, though a city like Perth does have a lot more open space to be able to have standard greenspaces.

There are studies that have shown that the effectiveness of greenspaces is “…subjective to effective geometry and width…”. This limitation of required area could cause a problem for cities that are quite dense, and ironically some of those cities have a greater need for these systems.

I combined my knowledge of the principles of ecological engineering, and thought why aren’t we utilising what we already know about the natural world? After all the reason we are having this issue in the first place is because the design of our cities inadvertently alters the natural order.  The way I see it is that the UHI effect isn’t just a result of many anthropogenic mishaps but also a representation of our lack of ability to incorporate ourselves with the natural environment.

survey of North American trees found that plants protect their ability to photosynthesise by maintaining a leaf  temperature of about 21 degrees, no matter the external environment. Plants use several mechanisms to do this, such as changing the angle of their leaves relative to the sun. This made me question why our built environments aren’t also flexible to adapt to an environment that changes so rapidly over short periods of  time? Why aren’t we creating design consistent with ecological principles, to mimic our natural environment (the second design principle).

And so I have chosen to pitch to you my suggestion in a Vlog, for possible ways we could mimic our natural environment to address UHI effect, please enjoy below:

The article about Fred and his kind.

Evaporation on its own can decrease peak summer temperatures by 1-5 degrees Celcius.  The maintenance and initial planting costs associated with greenspaces were estimated in a study on 5 US cities and their urban forestry programs to be 15-65 US dollars a year per tree. Imagine if we could come up with an idea like this one, a once off alteration to manufacturing and building our cities that could assist in decreasing the UHI effect. As soon as I had the idea I realised the limitations and that it too would have to be considered for each site separately (second principle). But I think that where we are falling short is the first principle, solutions that mimic nature. What other cooling mechanisms in the natural world could we mimic? Post any ideas for this below, I would love to hear them. I think it is important for us to consider alternative solutions in order for us to make positive change seem more desirable, possibly in this case, financially.

Maybe there are many other applications for this, possibly in water transport, I would love to know what you all think? Will ideas such as this one fit into the design principles for ecological engineering? Please post ideas/limitations or other comments below.

References for images used in video:


I Beg of Y’all: Drink from my Wetland

From what I am starting to understand about this magical concept of ecological engineering is that we need to integrate what we know or can learn about natural processes and the environment into what we already have and know about ourselves. The potential significance of what “we” or humans can learn from the natural world is clear, look at birds, then planes, the connections already exist, we just need to utilise them more, for our own benefit.

By some sort of accident, I found myself looking and thinking about the most efficient and complex ecosystems. I had studied zoology as one of my Undergraduate majors, so I thought back to what impressed me in the natural world back then. I came up with wetlands, a functioning ecosystem on a very efficient level. Wetlands are some of the most productive ecosystems on the planet, it has been estimated that even though wetlands are only 5-8% of the earths land surface, they account for 20-30% of the earths soil pool for carbon.

So how to incorporate an already existing efficient ecosystem function into the great cities of the world? I figured this could be important, as it is expected that 70% of the world’s population will live in urban centres by 2025.

I read an article discussing the future of “green cities”, something I found easy to get excited about. Literal green cities; an obvious step in the right direction but this article argued a valid point:

“…giving buildings a biological hairdo does not a green city make.”

image 1 vlog
sustainable “green city”

A city must focus on the integration of many systems to be truly utilising ecological principles, towards a “sustainable city”.

What are the Issues?

Let’s put some perspective on this first. The issue I thought could be addressed was the already costly system of getting potable, or safe drinking water, to where we want it but in a more ecological minded and cost effective way. Currently we are adding the cost for bringing clean water in, to the costs of then removing this water after use; we are effectively paying twice for our water usage. This is a very basic way to look at the current system in most of our cities. There are also costs associated with dealing with storm water, which can in some cases be linked directly to poor design of infrastructure, a growing concern with climate change and urban densification looming.

A clever man I came across during my research said something that stuck with me:

“…if more people take advantage of things like grey water systems and green roofs then our demand for water (and its disposal) may drop to the point that our infrastructure may no longer be completely necessary. Reservoirs, aqueducts and huge pipelines guiding water to major cities could wind up as over-built, archaic achievements of a different age”.

The Magic of Wetlands

image 2 vlog.png
Image from Natural Explorer and text

So how do these incredible systems work and what functions are the ones we can benefit from? A simple breakdown of wetland functions can be found in the above image. Also a little definition for in the box to the right. text 1 vlog 1

To find out more, or if don’t want to take my word for it, follow this link for the functions of wetlands on a local and global scale. And watch this home grown Aussie video made by the Department of Environment and Heritage, the Queensland Government.

We Can Make Wetlands

What I found interesting was the potential for wetlands for water purification. This is by no means a new idea, to use wetlands as a treatment process for our waste water.

First again some facts:

·         Globally, two million tons of sewage, industrial and agricultural waste is discharged into the world’s waterways

·         At least 1.8 million children under five years-old die every year from water related disease, or one every 20 seconds.

·         Wastewater treatment facilities in the United States process approximately 34 billion gallons of wastewater every day.

·         Only 1% of drinking water in many cities of western countries is used for actual drinking

·         In Australia we use 341, 000 Litres of water each year

These facts can be found here and here. text 2 vlog 1

In Australia, we have already used man made constructed wetlands to influence hydrology, decrease erosion and provide shade and reduce light availability for algal photosynthesis on our farms. See here to find out about Queensland’s Wetland plan for improving farm water runoff quality by addressing these aspects.

Through constructed wetlands the processes for the purification for waste water are as followed:

·         Phytoremediation- which is really a big word for using plants to remove contaminants in water. The plants take up the bad stuff through their roots, studies have showed that deeper root trees are also effective, as they can reach the contaminants at a deeper level. The other magic at this level is that the plants can also influence soil structure and characteristics by releasing organic substances that can alter chemical composition.

·         Microbiological Mineralisation – fancy talk for the activity of bacteria to encourage mineral formation

·         Filtration by gravel and gravity

A study conducted by Griffith University, Queensland, pointed out that in Australia very little of our sewage effluent is reused or recycled, that we tend to purify our water to then release it back into rivers and oceans. Our current disinfection processes with chlorine is not only expensive but also produces unnecessary by-products. The need is already there for a system that can remove pathogens whilst taking back nutrients and water from our waste water, it also has to be “environmentally sustainable, socially accepted and cost effective.”

A man I came a across a couple of times looking for information on sustainable cities was Jeff Speck, a city planner with a nice voice for these kind of things. He spoke about the use of wetlands to purify waste water and said that once the water has flowed through some of these wetland filtration systems:

“…the water is about as high-quality as potable water, but just to be safe, there is an additional mechanical filtration system that uses UV to blast out any remaining pollutants. The water can then be reused to water landscapes or sent back to households for toilets.”

Read more about Jeff and his work.

Tell Me How!?

I found a rather thorough study, published as far back as 1998 in the Netherlands, which considered the “Opportunities and Limitations” of the use of wetlands for waste water treatment. Check out my side box for the six steps to the purification process discussed in this study.text 3 vlog 1

The study found that one of their constructed wetlands in Holland received sewage from a total of 800 people and could remove 99% of the bacterial pollution, 80-90% of COD and BOD (see my lovely section to the left below) but only 30-40% of the nitrogen and phosphorus necessary. The facility was used for 10 years for the treatment of a recreational facility.

text 4 vlog 1See the diagrams below to get an understanding of how wetlands deal with phosphorus (right) and nitrogen (left):

Another study recently in Italy, 2005, compared the effectiveness of two methods of wetland waste water treatment systems.

1.. There is surface flow constructed wetlands, see the diagram below. All the action for these types occur in the upper layers and therefore can be a breeding ground for mosquitoes.

image 6 vlog 1
Surface Flow Constructed Wetland

2. The other type is subsurface flow, the one I consider more practical due to the potential for these to not be a health hazard or unpleasant (sometimes wetlands smell, I know) for the public to be near. Of this type, there are another two types that have been studied, also shown in the diagrams below. The first diagram (on the left), the vertical flow, rely on a controlled source of energy but take 2/3 of the space of the horizontal flow, (diagram on right), which has fluid circulating horizontally naturally. Both of these, so subsurface flow in general, require on average 80% less space than the surface flow.

Show Me Where?!

An intuitive natural progression from here is to bring these efficient systems into our cities, incorporating an entire natural ecosystem into our day to day lives or at least into the fabric of the city. Turns out this also isn’t a new idea, in fact one impressive lady from Morocco caught my eye through TED talks. Watch the video, it’s only a few minutes long I promise!

Aziza Chaauni, an architect presents a wonderful plan to reinvigorate and transform the Fez river and so the Medina (the old town area, which is actually a World Heritage Site) of Fez from

This:                                                                                                                 To something like this:

Her grand plan also included the use of a constructive wetland within the Medina area, in conjunction with the river as a self-filtering system for the area; much needed as originally the river was so polluted they had to cover it with concrete and you couldn’t drink from the running fountains that used to provide people with drinking water. The process is still ongoing but in an interview in 2014, Aziza said that there has already been improvement, particularly downstream from the Medina, where there has been noticeable changes in biodiversity. Also attitudes have changed from viewing the river as a river, not a sewer; craftsmen have stopped polluting the river (watch the video for more, but this was a central issue to the problem in the first place).

Read more here if you would like to find more information about the transformation of the Fez River.

For a quick summary of my favourite case study, and perhaps the most impressive application I could find of the use of constructed wetlands, please enjoy this vlog posted on YouTube.

Once you have watched the Vlog I am sure you will want to see an actual clear diagram of the Flowlands project found below.

image 12 blog 1.jpg

The proposed plan for the Gowanus River as explained in the video above. See here to zoom in on the image.


Now What?

I have already referred to the benefits of something like this for Australia and other western countries, to decrease costs of our water treatment and to also contribute to a more ecologically minded society but I also think that the possibilities for parts of the developing world are equally advantageous.

For instance, and I only think of Mumbai as I have spent time there recently, but in India less than half of its domestic waste water is treated. If there was a way to get this constructed wetland system to be so effective as to have the end result as potable water, the possibilities are exciting! A report from the General Pollution Board in March 2015 estimated that sewage generation from urban areas is estimated at around 62,000 million litres per day (MLD) whereas the total treatment capacity available is only 23,277 MLD. Also partially or untreated sewage is the largest contributing source for the decline of surface or groundwater quality, it contributes  to 70% of the pollution to streams or water bodies of India.

In Mumbai in 2016 the government was considering a new 6.39 kilometre sewage pipeline as part of a $300 million Mumbai Sewage Disposal Project. Imagine if this large amount of money went towards a design such as Flowlands that could benefit the community is so many other ways and was in line with ecological design principles. The system could be self sustaining, in that it could provide a certain area with water as well as treat the water coming out as waste. A small notch in a larger problem for somewhere like Mumbai but the benefits of these designs being space conscience is crucial for a city as dense and complex and Mumbai.

The clear benefits here of integrating ecological principles into engineering design are not only environmental but economical and, as with Aziza’s plan for the Fez, can be social too.It can also integrate an aspect of humanitarian engineering for the benefit of the people long term as well, to possibly assist in increasing peoples standard of living.





The Principles of Ecological Engineering

I would like, in these blogs, to investigate the principles of ecological engineering and what they can mean for the future of engineering or to me, as an engineering student. The principles I will be using as a base for these investigations are as below, found in an article by Bergen et al, Design Principles for Ecological Engineering. It is a great read and I have found these principles as an excellent guide to interpreting the value of engineering projects.

  1. Design consistent with ecological principles
  2. Design for site specific context
  3. Maintain the independence of functional requirements
  4. Design for efficiency in energy and information
  5. Acknowledge the values and purposes that motivate design

The first point is the importance to take advantage of, mimic and include natural systems into our engineering design. To read more about these principles read here.