Smart cities: maintenance and management of public green spaces
Urban green spaces in contemporary culture are no longer seen only as an aesthetic element, but also a factor in combating pollution, industrialization and anthropization. Maintaining green areas is a delicate balance between environmental and economic sustainability, which is why machines with electric motors are increasingly used
Over the past centuries, the value of urban green spaces, in particular trees, was primarily considered according to the production that could be obtained. Colbert, minister of Louis XIV, in the mid-seventeenth century, argued that the oaks he had planted in Paris would be used for the construction of the Royal Navy ships of future centuries. Today the value given to public green spaces has changed completely, and is aimed at elements that have to do with the environment, the landscape, the territory and quality of life. This is because, with the growth of environmental culture, we have become increasingly aware of the many functions of urban green spaces, whether these consist of lawns, trees or tree-lined streets. Their functions range from eco-environmental to architectural and aesthetic, from social and recreational to cultural and educational, from hydro-geological protection to health and hygiene purposes. Urban green space is therefore understood not only as an aesthetic and landscape element, but also as a protective element against the effects of climate, industrialization and anthropization, as well as a factor that encourages socialization in addition to protecting a certain type of city wildlife, which would otherwise be destined to disappear.
Types of green
In urban areas, we encounter different types of green. Firstly, we find green spaces defined as decor, which represents the largest portion of green in a city. This category includes urban parks, historic gardens, the green of roads and river banks, tree-lined streets, the green of traffic islands, roundabouts and neighbourhoods. Next, the category of functional green includes green spaces with specific uses such as sports, education, health, burial, and even urban vegetable gardens. Finally, there is the category of private and residential green spaces, which is expanding with new types, such as vertical and roof green. For example, green façades on buildings; the first forest-building was built in Turin, drawing attention not only nationally but also internationally. Plants were used for the façade, with structural elements that support large wooded roofs. Green areas created this way are coupled with a series of technological solutions to save energy and water, as well as improving the comfort of the inhabitants.
After all, urban green is an essential component of the growing technological innovation aimed at creating new Smart Cities.
The different types of green require specific forms of maintenance and management, given that the urban environment is not conducive to the development of vegetation, due not only to pollution, but also for the poor soil conditions. This means that the different plant components, and especially trees, grow slowly, which makes them more susceptible to pests. This gives rise to the need to know, including through the use of new methodologies and targeted and non-invasive instrumental analysis, the vegetative state and health to be able to implement the correct routine and extraordinary maintenance.
In considering the maintenance and management of urban green areas, it is necessary to distinguish horizontal green surfaces (lawns, flower beds, etc...) from vertical green (shrubs, trees, etc...), to identify the different needs and different machines and equipment to be employed.
Maintenance of green surfaces
The turf of parks and gardens is the main component of horizontal green, both in terms of size and in terms of maintenance costs. In urban parks, for example, this burden accounts for approximately 80% of the total cost of maintenance. As regards mowing, the height and frequency of the cut depends on the type of turf, be it ornamental, recreational, sports, etc.; while the size of the turf influences the type of lawn mower used, that is, with the driver on the ground or with the driver on board.
The mowers used for ornamental turfs that require cuts at a height of no more than 20-25 mm, and thus with a high cutting frequency, are those with cutting apparatus equipped with helical blades, or even those that provide mulch mowing. Over certain minimum heights (25-30 mm), machines with horizontal blades rotating on a vertical axis are used with good results on the different types of turf. Machines with rotating blades on a horizontal axis is suited for demanding turfs and for those with low utilization, as well as rustic ones along embankments, which are maintained with articulated tool-holding arms. The mowing equipment employed for sports turf, such as golf courses, uses helical blades, albeit with a different number of blades, since the cutting heights are between 3-6 mm for greens and 15-18 mm for fairways.
The use of lawnmowers with driver on the ground is conditioned by the size of the lawn. In general terms, it is safe to say that this type of mower is employed on surfaces smaller than 1500-2000 m2. Particularly in private gardens, the use of robotic mowers is increasingly widespread. Above 2000 m2, lawnmowers with driver on board are generally used, both for mulch mowing and for mowing with basket grass collection. This includes small tractors and ride-ons, with different widths for the mowing equipment.
Other routine maintenance operations include fertilization, whose frequency and amount of fertilizer varies not only depending on the species and variety of grass, but also in relation to the management of the cuts (frequency and height) and the nature of the terrain. For large lawns, the fertilizer spreaders employed are no different from those used in agriculture.
Extraordinary maintenance operations are those that aim to prevent degradation or that take place when its first symptoms appear. These essentially consist of defelting operations, carried out with machines that remove, with spaced vertical cuts, that part of the non-degraded biomass layer which makes the soil impervious to water, as well as aeration operations carried out with aerating or coring machines, in order to reduce excessive soil compaction.
Routine maintenance includes the cleaning of lawns as well as the roads and sidewalks that run through parks and gardens, or tree-lined streets. It basically consists in collecting leaves and other debris. The fall of leaves is progressive in relation to the species and climate conditions. For deciduous plants, it lasts for several months (autumn-winter), while for conifers the period is almost yearly. In any case, with the onset of low temperatures and on windy days, the fall increases. The volumes are high; on average 1.4-1.8 m3 of leaves per adult tree. The most widely used machine in this operation machine is the blower, with which the leaves are conveyed into piles to be subsequently collected.
For paved or gravel roads that run through gardens and parks, weeding is an operation that becomes necessary. The tendency is to abandon chemical treatments with glyphosate, replacing them with the use of pyro-herbicide or with biodegradable foam base treatments, high-temperature water (100-120°C), steam, as well as infrared.
Vertical green maintenance
For hedges, shrubs and trees, the routine maintenance operations consist in pruning. In the case of hedges and shrubs, hedge trimmers are generally employed, performing any finishing with shears and scissors, which are generally pneumatic. As regards the pruning of adult trees in parks and tree-lined streets, the frequency is every few years. The tendency is to reduce its intensity, while the work site normally consists of: special aerial platform on which the pruner operates with a chainsaw; wood chipper driven by a tractor and fed by the tractor driver who does the clearing; tipping truck equipped with a box to collect the wood chips.
The evaluation of the stability of trees has taken on increasing importance, owing to the age of the city tree population and the intensification of extreme weather events, such as high winds and “water bombs”. The breaking of large branches and even the fall of whole trees that cause damage to people and property are becoming increasingly frequent. Methodologies and tools have been developed for this purpose, such as the tree tomograph, which is used to make accurate and non-invasive diagnoses. This equipment allows to know the full situation inside the trunk and between trunk and root, detecting the presence of cavities, decay, or simple internal discontinuities of the wood. The data provided by the sonic tomography is displayed in real time, with specific software applications on a PC or on a tablet, with images in 2D or 3D, in order to reveal the tree’s internal condition and assess its stability and safety.
Smart Cities and management of green spaces
The management of maintenance requires finding the right balance between environmental sustainability and economic sustainability, as well safeguarding the safety of workers and citizens. This has led to the increasing use of machines with electric motor, whose presence on the market is constantly growing. As far as pest control is concerned, the use of biological control and integrated pest management has increased, thus reducing the consumption of pesticides.
In more strictly operational terms, we witness the use of differentiated management, where the operations are scheduled according to the quality of the green and its use, thus reducing them significantly without it resulting in a reduction in the quality of the green spaces. To implement the management of risks related to the fall of trees, some municipalities in Italy have also started to implement risk management systems, which represent a rational system for implementing maintenance and management that can reduce the danger that may arise from the trees in an urban setting.
It is worth mentioning that the number of the world’s citizens is constantly increasing: according to the forecast, in 2030, 70% of the world’s population will live in cities. We must therefore be able to meet the demands and needs of a growing number of inhabitants. In addition to making cities increasingly Smart, we will have to offer good quality of life, and together with the need to ensure good maintenance of the existing green spaces, we will also need to create new parks, new gardens and collective urban gardens with a social and ethical function. There are plenty of examples of this. The VanDusen Botanical Garden is exceptional, located at the centre of the city of Vancouver, Canada. The garden’s Visitor Center is a building that covers an area of 164 m2, with a high-efficiency energy design, whose carbon footprint is zero due to the production of energy from renewable sources and the green roof on which plants of different species and varieties were planted. Its self-sufficiency also concerns the water needed for irrigation and toilet facilities, achieved through the collection of rainwater, which is first purified and then distributed. In Europe, France is one of the countries most attentive to public green. In Grenoble, for example, the City Council is implementing its strategy for transforming the city into a Smart City by giving green spaces an important role, including the removal of billboards replaced by trees. The use of urban gardens for family and collective use is an increasingly adopted solution. One example comes from the city of Nantes, which invests heavily every year to improve and increase its already rich green heritage. Aware of how the role of green spaces is not only environmental but also social and educational, every year it increases the number of gardens and family and community gardens in urban areas.
Recently (September 2016), Turin inaugurated what was, for three months, the first Italian Smart Square. A square transformed into a laboratory for testing smart technologies created by a Turin company. Once tested, these technologies are intended for Brazil, for the new Social Smart City of Fortaleza. These include benches connected with sensors installed in the car parks, which report through an app if there are free spaces; streets with hi-tech cobblestones that are charged with energy by day and light up at night to show the path; apps that can be downloaded to iPhones to allow citizens to schedule group events or to know the consumption of electricity for street lights and water for irrigation; gardens with fruit trees and vegetables, watered as needed with the right amount of water. The gardens we allocated to citizens who ensure their cultivation. The aim is not only productive, but also educational for citizens and, above all, for children.
