3.3. Datos estructurales
3.3.3. Tetracoordinados: correlación entre el grado
Darlow et al., (2003) stated that the multi-functional benefits of SUDS can be maximised by adopting an integrated approach to planning by groups such as local planning authorities, water service providers, environmental regulators, engineering consultants and NGO’s. They concluded that a holistic approach to the management of
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surface water which includes SUDS and their associated watercourses can provide significant environmental gains. Fig. 2.3 presents the various benefits of SUDS.
Fig. 2.3: SUDS benefits (Adapted from CIRIA, 2010).
Many researchers have considered the benefits of SUDS in terms of the following categories, which are not mutually exclusive but can overlap and reinforce one another (CIRIA, 2013):
1. Direct economic value – e.g. increase in land value and decrease in house insurance policies due to flood reduction; increase in fisheries production, etc. due to pollution control (e.g. Penning-Rowsell et al, 2005; Kenny et al., 2006).
2. Increase in aesthetic and amenity value due to additional green space (e.g. Natural England, 2009; 2013)
SuDS
Flood risk managemen t Water quality management Amenity and biodiversity Water resources Community Recreational Educational Enable development20
3. Increase in environmental or ecosystem value due to less stress on the environment or the emergence of new biodiversity in urban areas – which relates to ecosystem services (Sukhdev et al, 2010).
4. Diversification of social benefits which tend to be less easily quantifiable (SROI, 2012)
2.4.1. Flood Risk Management
Sustainable drainage involves managing rainwater (including snow and other forms of precipitation) with the aim of:
(a) Reducing damage from flooding (b) Improving water quality,
(c) Protecting and improving the environment, (d) Protecting health and safety, and
(e) Ensuring the stability and durability of drainage systems (HMSO, 2010).
The effects of climate change will continue as extreme weather events and global warming become more apparent. In recent years the UK has seen an increase in the number of flood events and flood risk warnings in many areas. Approaches to limiting disruption and damage from flooding are changing significantly from a strategy of flood defence to one of flood risk management using combinations of sustainable drainage system techniques (Defra, 2014).
The strategies for Natural Flood Management rely on one, or a combination, of the following fundamental mechanisms:
Storing water through the use of ponds, ditches, embanked reservoirs, channels or land;
Increasing soil infiltration, thereby reducing surface runoff (Defra, 2008), although this can be counterbalanced by greater subsurface flows. Free-
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draining soil will make saturation less likely, and evaporation from soil will make space for more water to infiltrate;
Slowing down water speed by increasing resistance to its flow, for example, by planting shrubs, grasses or riverside woods;
Limiting joining-together of water flows by interrupting surface flows of water, for example, by water storage or planting buffer strips of grass or trees.
2.4.2. Water Quality Management.
Human activities usually lead to producing numerous pollutants (such as sediments, litter, pesticides, fertilizers, oil, animal waste, and other forms of chemicals) which can easily cause diffuse pollution and can adversely affect the environment. Traditional piped drainage systems are not built to manage these forms of pollutants, and therefore they are washed into sewers and eventually watercourses in surface water runoff, making it difficult to comply with water quality legislation (CIRIA, 2010; Freni et al., 2010).
Some SUDS techniques, such as permeable pavements, filter drains, bio-retention, swales, ponds, wetlands, etc., provide water quality improvements by reducing sediments and contaminants from runoff either through settlement or biological breakdown of pollutants (D’Arcy and Frost, 2001; CIRIA, 2010; Segaran et al., 2014.
2.4.3. Amenity and biodiversity.
Some SUDS techniques such as wetland and pond systems are primarily constructed for improving water quality and reducing the quantity of run-off to receiving watercourses. However, they also have the potential to contribute value in terms of amenity and biodiversity in urban areas (Briers, 2013). In general, it has been found that
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they are capable of supporting a respectable number of species of both animals and plants (Hansson et al., 2005; Vermonden et al., 2009; Le Viol et al., 2009).
Bastien, Arthur & McLoughlin (2011) carried out a survey, through the application of a structured questionnaire, about the potential value to residents of living in close proximity to a SUDS pond. Their findings indicated that people generally prefer to live close to ponds or regularly visit ponds in their vicinity, and are attracted most because of pond’s wildlife. Their results also show that although the pond’s characteristics are not the main factor influencing the choice to move into an area, but its effect is markedly positive.
There is an increasing pressure on planners and developers to design to provide green infrastructure and green spaces. SUDS can help in meeting this challenge and improve development by creating habitats that encourage biodiversity and simultaneously provide open green space (CIRIA, 2010; Andersson and Colding, 2014).
2.4.4. Water Resource Benefits
Some SUDS techniques that soak water into the ground can also recharge underground aquifers where there is no risk of polluting the aquifer (CIRIA, 2010). To be more specific, SUDS can capture, or harvest rainwater that can be used for functions that do not require treated water from the mains (for example, cisterns for flushing toilets, irrigations, etc). This may in effect contribute to water efficiency and, depending on the scale of the system, can contribute to localised flood risk management (CIRIA, 2010).
2.4.5. Community Benefits
Green infrastructure is, in the main, a public resource, available for use by the 80 per cent of the population who live in towns and cities (Forest Research, 2010). Green space, ponds, etc, have potentials for enhancing social cohesion; they can bring people together,
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and can improve community cohesion especially as different social groups engage with each other.
Wetlands can also serve as wildlife parks with stepping stones, boardwalks and islands. Similarly, ponds with foot paths, benches, picnic tables, etc, can also be exciting social and recreational areas. Ponds and wetlands will be assets to the community, enhancing the quality of life, by providing attractive and calm green space within the built environment CIRIA, 2010).
2.4.6. Recreational Benefits
Good quality, accessible green space and infrastructure can provide many potential health and wellbeing benefits (Velarde et al., 2007). The most significant of these can be grouped into three broad categories (Forest Research, 2010): (1) increased life expectancy and reduced health inequality; (2) improved levels of physical activity and health; and (3) promotion of psychological health and mental well-being. Access to green space has been found to raise levels of physical activity, which in turn improves individuals’ health. Green space can also have a beneficial impact on mental well-being and cognitive function (Velarde et al., 2007). The evidence strongly suggests that, at their best, green spaces can help reduce health inequalities and that both the improvement of existing, and creation of new, green infrastructure should be prioritised, especially in areas of greatest need.
2.4.7. Educational Benefits
Barbosa et al (2012) concluded that SUDS should be seen as an opportunity for development and improvement of social, educational and environmental conditions in urbanized and surrounding areas. Many SUDS components have been used for recreational and educational purposes with schemes located in school playgrounds
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(CIRIA, 2010). Some schools include SUDS to manage surface water that also provides an invaluable in-situ learning resource about water.
2.4.8. Development Benefits
Ling et al. (2007) have explored how a multifunctional approach to spatial planning of SUDS (drawing upon historical, ecological, communitarian, economic, and aesthetic functions) could underpin more sustainable regeneration in post-industrial landscapes. Delivery of SUDS can enable the granting of planning permission to developers. SUDS can provide savings on the overall construction and maintenance of drainage schemes (CIRIA, 2010).
Bastien, Arthur & McLoughlin (2011) carried out a contingent valuation of the benefits of ponds and found out that the additional value brought by SUDS amenity, when monetised, can offset a pond’s initial construction costs and ongoing maintenance, hence ensuring the return on investment for developers.