In his latest column for Greenscape, Dr Tom Young, Blue-Green Infrastructure Associate at TEP, reports back on his extensive travels investigating water security across the agricultural, horticultural and landscape sector, as well as his findings on green roofs in different parts of the world…
In 2021, I was lucky enough to receive a Nuffield Farming Scholarship investigating water security across the agricultural, horticultural and landscape sector. This has mainly focused on water efficiency measures such as drip irrigation, advanced spray irrigation systems and land management. I also saw lots of great examples of alternative water sources such as recycled wastewater and even fog water – and after some research, I can report that gin made from fog water is excellent (see below).
Above: Gin made from fog water
The travel scholarship allows a recipient to travel around the world to broaden their knowledge and experiences, whilst also being part of large and well-respected organisation. It’s definitely something I would recommend to anyone, and would be happy to speak to potential applicants about my experiences. I also used my travel time to meet green roof colleagues around the world and see what work they have been up. So, below I’ve brought together a round-up of my experiences whilst abroad for readers…
In Athens, Dr Nikolaos Ntoulas showed me some of the work he has been carrying out to utilise different sources of water to irrigate semi-arid green roofs. The studies showed that flood irrigation using sea water can be used to keep salt tolerant green roofs alive in extreme drought situations (Ntoulas & Varsamos 21). Although salt levels will be harmful in the long term, the heavy irrigation cycle helps to prevent salt build up in the substrate as quickly as when sea water was applied at a normal rate. This work shows promise in certain climates with regards to relieving stress on freshwater supplies during high demand periods. Dr Ntoulas and colleagues are also investigating the benefits of using recycled grey water from a domestic property on a green roof. Grey water is made up of sink, shower and washing machine wastewater, and can have high levels of salt and other contaminants. This work is ongoing and shows great promise in reusing a completely viable source of water.
Above: The Stavros Niarchos Foundation Cultural Centre, Athens.
When I was in Athens I also took the opportunity to visit the Stavros Niarchos Foundation Cultural Centre (above), a sprawling green roof and urban park area covering 25 ha. The well-designed system acts as a public park with turf areas, formal planting and even an established olive grove! A substrate layer up to 1.2 m and a drip irrigation system are used to maintain this landscape during the peak of summer, which can be extremely hot and dry. However, it shows how well-designed green roofs can be truly multifunctional spaces, even in harsh climates.
I was only in Denver for one day, so didn’t get a chance to meet the amazing Dr Jen Bousselot or visit the stunning campus green roof. But I did manage to speak to Jen when back in England about the interesting work on bio-solar roofs which also grow crops. Talk about stacking services! In short, green roofs help solar panels increase their output and solar panels can help green roofs by providing shade, reducing water loss, and increasing the ecological diversity of a roof. Water can also be collected and diverted from panels to help grow vegetables. Figure 3 (below) shows a picture of their amazing demonstration roof.
Above: Terra Green Roof at CSU Spur Colorado State University
When I was in Phoenix, Arizona, I managed to catch up with Scott Jeffers from Anthroeng, a very talented stormwater modeller with a lot of experience modelling flows through green roof systems. Scott showed me some really exciting examples of the wider drainage and gas network modelling he does for clients, with green roofs adding a nice extra stormwater management system within these.
Above: Pictures from thePhoenix Desert Botanical Garden.
I would also highly recommend a visit to the Desert Botanical Garden if you are ever in Phoenix. Founded in 1937, the garden now has over 50,000 desert plant specimens from around the world, with plenty of photo opportunities which unfortunately this article cannot do full justice to.
Above: Tiled roof on Tenerife with giant succulents!
I didn’t see too many green roofs in the Canary Islands, apart from this great example of a traditional tiled roof being taken over by a monster succulent (above)! I did manage to connect with Silvana Amezquita though, who is a green roof architect who lives on the islands and has a lot of experience in Spain. Silvana has set up the Addgreen Project (see flyer below) to help architects understand the opportunities that urban greening provides. If you are looking to build a Mediterranean green roof and need a hand designing it, I suggest Silvana.
Above: Porxos d’en Xifre 1000m2 extensive roof garden, winner of the Barcelona City Council green roof council award.
Above: Flyer for Addgreen and Eixverd training courses for green roofs in Spain and Mediterranean climates.
Silvana put me in touch with Lidia Calvo, who set up a female-only social enterprise company based in the heart of Barcelona specialising in green roof design and installation called Eixverd. Due to the nature of communal flat buildings in Barcelona, a common problem – despite generous city grants – is getting everyone within the building to agree to the green roof proposals. Despite this, Eixverd have some amazing examples of roof gardens utilising the flat and structurally sound roofs common in the city.
Above: Agamon Hula visitor centre turf roof in Israel.
I didn’t manage to meet any green roof professionals in Israel but did come across this interesting turf roof (above) which formed a nice entrance up onto the Agamon Hula visitor centre roof. This is a large nature reserve and wetland area which is home to numerous migratory bird species and helps to filter and clean agricultural runoff prior to entry into the Sea of Galilee.
Above: Urban greenery in Singapore.
Above: The Jewel at Singapore International Airport.
Above: Green roof at Singapore Botanical Gardens.
Singapore was a smorgasbord of green infrastructure, from high-rise green walls to fully mature trees on private balconies. The city is blessed with a high temperature, high rainfall climate, which allows year-round growth. I spotted a number of great examples in the World UNESCO Botanical Gardens which look like a nightmare to keep under control, as well as more turf parks and green walls. There was also the quite frankly insane waterfall and green terraces at The Jewel which is actually inside the airport (above).
Above: Green roof substrate research with and without biochar at different planting densities of Ficina nodosa under a simulated rain regime. Photo courtesy of Joerg Werdin.
I was lucky enough to stay with my friend Dr Joerg Werdin and his amazing family in Melbourne. I met Joerg in Sheffield over ten years ago, and since then he has worked in a variety of green infrastructure roles at the City of Melbourne Council. He has also impressively completed a part time PhD looking at the use of biochar as an amendment to green roof substrate. His research has found that although showing real promise in laboratory experiments, a lot of these benefits don’t seem to materialise in field trials (above). There’s still plenty of application in green infrastructure in terms of pollutant removal, but as a water retention additive, much more commercially viable alternatives seem to exist. His research campus also has a brilliant communal green roof, which he assures me is excellent for Friday night beers, a key green roof service (below).
Above: The green roof at Melbourne University Burnley Campus. Image courtesy of Glamour Inhabitat.
Joerg also introduced me to Ben Nicholson and Gail Hall who are the Co-Founders of the Australasian Green Infrastructure Network (AGIN), a new organisation which aims to connect Australasia’s green infrastructure professionals to combine research and practice. If you are in Australasia, I highly recommended getting in touch with them.
In summary, a highly valuable experience meeting practitioners from around the world and expanding my green roof network. I would really encourage anyone to embrace similar opportunities as you are never sure where it may take you.
More information on Nuffield Farming Scholarships can be found at: