Authors: Joseph Williams & Jesper
Fahlström
Impervious surfaces in cities are
surfaces that do not allow water infiltration, and instead cause runoff. The
lack of water infiltration causes long-term soil degradation and stresses
expensive water management systems.[1]
These surfaces also collect and hold on to heat, causing higher temperatures in
urbanized areas, known as the Urban Heat Island (UHI) effect. Common examples
are asphalt and concrete, which includes most streets, sidewalks, and parking
places. These surfaces have covered more and more area over time. For example,
in the Brussels Capital Region, impervious surfaces covered 26% of land area in
1955, which grew to 39% in 1985 and 47% by 2006.[2]
In order to reverse this trend, impervious surfaces can be replaced by
permeable ones which allow water infiltration and reduce the UHI effect. Many
impervious surfaces are used to support transportation infrastructure, so here
we explore how greener, permeable surfaces can be used in this context instead.
Green tram tracks
Photos: Brussels Tram 1 & Brussels Tram 2
Tram tracks are one of the urban
spaces where green- and transportation infrastructure can functionally
co-exist. Hence, green tram tracks have increasingly been applied in urban
areas over the last decades in multiple cities, creating “green corridors” in
areas with normally very sparse amounts of vegetation. It is a prime example of
an innovative solution to combine the environmental benefits of greenery with
the functionality of the mobility sector. The implementation of vegetation in
between the tracks can result in multiple benefits in terms of ecosystem
services, including water retention, microclimate regulation, improved
biodiversity and noise reduction, just to mention a few examples.[3]
And let's not forget the fact that it’s much easier on the eye as well - right?
The element of vegetation on tramways can also lead to other socio-economic
benefits, perhaps, the most important is the expansion of greenery in general,
which leads to a positive effect on the well-being of urban
dwellers.
As greenery and trams can co-exist on
a larger scale, it therefore poses an opportunity to green cities in
environments where possibilities are limited. However, there are some
challenges and barriers to its application. Besides the costs of the
implementation, it also requires substantial costs in maintenance to maintain
high-quality vegetation. However, there have been in progress in more recent
years to propose more low-maintenance alternatives to grass, often consisting
of sedum. This is the case in Warsaw, where low maintenance green tram tracks
have proved to both be successful as an approach to both green a city in a
socially accepted way and keeping maintenance costs low.[5]
It also provides some beautiful color, don’t you think? Hopefully, we will see
even more of this in the future.
Photo: Warsaw Tram Tracks Sedum
(Source: Vegetalid
web page, n.d. Green lines along the tramway tracks)
Green Parking Lots
Parking lots and spaces offer another
opportunity to replace gray infrastructure with greener alternatives. Runoff
from impervious surfaces such as parking lots strains stormwater management
systems. Meanwhile, the increase of land coverage in cities over time is linked
to declining soil health, harming the ability for soil to filter out pollutants
and retain water.[6] At
the same time, parking lots retain heat from the day and release it at
night, thus contributing to the Urban Heat Island effect.[7]
Photos: Parking 1 Pattern & Parking 2
Green parking lots can help fix each
of these problems. First, they allow water infiltration, which decreases runoff
and reduces the risk of flooding. This also lowers the strain placed on traditional
stormwater management systems. Second, increased green space helps improve soil
health over time. Healthier soil is better at retaining water, and at filtering
out pollutants. This further reduces the strain placed on stormwater
infrastructure. Finally, green parking lots have been shown to drastically
reduce the UHI effect. As a result, our cities are more comfortable and
resilient in the face of climate change.
The amount of land taken up by parking
lots can vary by city, but certainly a lot of impervious land would be
reclaimed by transitioning from gray and impervious parking lots to green
parking lots. Similarly, installation costs and ecosystem service improvement
can vary by city. What is clear though is that the installation costs of green
parking lots are offset by the improvement in water retention. Improved soil
health and reduction of UHI effect are icing on the cake.
Photo: Green bike-walk path
Finally, the same technology could be
extended to spaces for bike parking to further decrease runoff and other
harmful effects. Even sidewalks and streets could incorporate some green and
permeable pavement. While each parking space and bike lane is not much
additional green surface, at the city scale this would drastically improve soil
health. Therefore, many impervious and UHI-causing surfaces can and should be
replaced, leaving us with greener, cooler, and healthier cities.
Photos: Mexico City & Gothenburg Bus Stop
(Source: Naturalwalkingcities web page. n.d. Mexico’s Green
Cities – Promoting urban walking and interaction with nature)
(Source: Landets fria, 2022. Bättre stadsmiljö med gröna
busskurer)
There are even further examples of how
cities have successfully incorporated greenery within the same space as the
transportation sector. Above are pictures of two examples, with quite varying
degrees of greenery added. The left picture shows a street in Mexico city where
roadside vegetation is used as barriers between cars and pedestrians, alongside
a large amount of big trees, almost creating a feeling of a forest/jungle in a
trafficked street. The right picture instead shows Gothenburg’s implementation
of sedum roofs on all their tram/bus stops, which are intended to create small
“sanctuaries' ' for insects all around the city.
So to the big question: can mobility
infrastructure also be green infrastructure? The short answer is, yes!
Integrating greenery into tram tracks, parking spaces, sidewalks, and even bus
stop shelters can replace impervious surfaces with permeable ones, providing
invaluable ecosystem services. In our efforts to make cities more liveable, and
especially in the face of a changing climate, it is imperative to make these
changes wherever we can. Doing so will make our graying cities just that much
greener.
Bibliography
Bouzouidja, R., Leconte, F., Kiss, M., Pierret, M.,
Pruvot, C., Détriché, S., Louvel, B., Bertout, J., Aketouane, Z., Vogt Wu, T.,
Goiffon, R., Colin, B., Pétrissans, A., Lagière, P., & Pétrissans, M.
(2021). Experimental Comparative Study between
Conventional and Green Parking Lots: Analysis of Subsurface Thermal Behavior
under Warm and Dry Summer Conditions. Atmosphere, 12(8), Article
8. https://doi.org/10.3390/atmos12080994
Green Parking Lot Resource Guide. (2008). US EPA.
Haase, D. (2009). Effects of urbanisation on the water balance – A
long-term trajectory. Environmental Impact Assessment Review, 29(4),
211–219. https://doi.org/10.1016/j.eiar.2009.01.002
Hamdi, R., Deckmyn, A., Termonia, P., Demarée, G. R., Baguis, P.,
Vanhuysse, S., & Wolff, E. (2009). Effects of Historical Urbanization in
the Brussels Capital Region on Surface Air Temperature Time Series: A Model
Study. Journal of Applied Meteorology and Climatology, 48(10),
2181–2196. https://doi.org/10.1175/2009JAMC2140.1
Jakubcová, E., & Horváthová, E. (2020). Costs and benefits of green
tramway tracks. Scientia Agriculturae Bohemica, 51(4), 99-106.
DOI: 10.2478/sab-2020-0012
Onishi, A., Cao, X., Ito, T., Shi, F., & Imura, H. (2010). Evaluating
the potential for urban heat-island mitigation by greening parking lots. Urban
Forestry & Urban Greening, 9(4), 323–332. https://doi.org/10.1016/j.ufug.2010.06.002
Sikorski, P., Wińska-Krysiak, M., Chormański, J., Krauze, K., Kubacka,
K., & Sikorska, D. (2018). Low-maintenance green tram tracks as a socially
acceptable solution to greening a city. Urban Forestry & Urban Greening,
35, 148-164. https://doi.org/10.1016/j.ufug.2018.08.017
Xu, C., Rahman, M., Haase, D., Wu, Y., Su, M., & Pauleit, S. (2020).
Surface runoff in urban areas: The role of residential cover and urban growth
form. Journal of Cleaner Production, 262, 121421.
https://doi.org/10.1016/j.jclepro.2020.121421
No comments:
Post a Comment