Urban Sustainability and River Restoration

Green and Blue Infrastructure

Katia Perini, Paola Sabbion

• Publisher: Wiley-Blackwell
• Year: 2016
• ISBN:
  9781119244943
• Edition: 1
• Topic: Economia
• Subtopic: Sviluppo sostenibile

Urban Sustainability and River Restoration: Green and Blue Infrastructure considers the integration of green and blue infrastructure in cities as a strategy useful for acting on causes and effects of environmental and ecological issues. River restoration projects are unique opportunities for sustainable development and smart growth of communities, providing multiple environmental, economic, and social benefits.This book analyzes initiatives and actions carried out and developed to improve environmental conditions in cities and better understand the environmental impact of (and in) dense urban areas in the United States and in Europe.

Part B
Strategies and Techniques

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Chapter 6 Green and Blue Infrastructure – Vegetated Systems

Chapter 7 Green and Blue Infrastructure – Unvegetated Systems

Chapter 8 Urban River Restoration

Chapter 9.1 The Bronx River, USA – Strategies and Techniques

Chapter 9.2 Los Angeles River, USA – Strategies And Techniques

Chapter 9.3 Madrid Río, Spain – Strategies and Techniques

Chapter 9.4 Paillon Nice, France – Strategies and Techniques

Chapter 9.5 River Thames, England – Strategies and Techniques

Chapter 9.6 Emscher River, Germany – Strategies and Technique

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Chapter 6
Green and Blue Infrastructure – Vegetated Systems

Paola Sabbion

6.1 The role of GBI vegetation

Vegetation plays a key role in the implementation of green and blue infrastructure (GBI) because it provides a wide range of ecosystem services (as described in Chapters 1–5). GBI involves multiple environmental benefits and curbs climate change (through energy use reduction; climatic modification; temperature decrease; shading; evapotranspiration; wind speed modification). It also contributes to air quality improvement (emission avoidance; carbon sequestration; pollutant removal); water cycle re‐naturalisation (canopy interception; flow control; flood reduction; soil infiltration and storage; water quality improvement); soil improvement (permeability increase; soil stabilisation; nutrient cycling; waste decomposition); biodiversity enhancement (habitat and corridor creation; species diversity fostering); food production (productive agricultural land and urban agriculture development); other economic benefits (property value rise; ecosystem service value; commercial vitality); social benefits (human health and well‐being improvement; physical, social and psychological side‐effects; community and cultural vitality; visual and aesthetic beautification.

GBI proves to be so effective also thanks to vegetation performing a number of hydrologic functions within the natural water cycle. For this reason, vegetation has become an important component of the Water Sensitive Urban Design (WSUD) strategies in Australia and of the Best Management Practices (BMPs) and Low Impact Development (LID) in the United States. These systems and related guidelines seek to replicate the natural water cycle in urban areas (see also Chapters 7 and 12). Hydrologic functions provided by trees and plants are canopy interception, stemflow, soil infiltration, evapotranspiration, hydraulic lift/redistribution, groundwater recharge, and conveyance of large storms (Figure 6.1). Water quality can similarly be improved by natural systems filtering pollutants (Benedict and McMahon, 2001). Vegetation plays an important role with regard to biofiltration, as it enhances the capacity of soils to remove pollutants through a combination of biological, chemical, and physical processes (Riser‐Roberts, 1998; Pilon‐Smits, 2005). All these benefits can restore the ecological condition of urban rivers reduce overflow and flood risk, and increase water quality to enhance and protect biodiversity.

Selection of vegetation employed for GBI is based on the appropriateness of a plant according to the site conditions and programmatic requirements (its specific horticultural needs, its role on the site and in a larger plant community). A viable selection considers on‐site climate, soils and hydric conditions as well as potential interactions between species, and future maintenance needs. For example, on a site that is likely to accumulate excess water it is necessary to identify and grow plants coming mostly from wetland communities. If the soil is contaminated by organic and inorganic pollutants, species to address phytoremediation should be selected (Calkins, 2011).

Figure 6.1 Role of Vegetation in the Natural Hydrologic Cycle.

6.2 Multifunctional ecological systems in urban areas

The ecological structure of landscapes, according to ecologists, consists of matrix patches (the dominant feature) and relevant connecting corridors. Large patches should be preserved in urban areas to increase biodiversity and form new connections between the remnant patches and ecological/habitat corridors (Barnes, 1999). Corridors are often termed as habitat corridors, wildlife corridors, or ecological structures. Planning habitat corridors, linking patches with surrounding environments, can contribute to increase biodiversity and ecosystem health (see Chapter 5). Developing ecological networks revolves around a set of ecosystems, linked in a spatially coherent interconnection through the flows of organisms, and interacting with the landscape matrix in which they are embedded. This is a means of alleviating the ecological impacts of habitat fragmentation. For this reason, biodiversity conservation strategies are an integral part of sustainable landscape promotion (Opdam et al., 2006). The elements and components of green infrastructure allow the improvement of ecosystem health, defined as the occurrence of normal ecosystem processes and functions, free from distress and degradation, maintaining organisation and autonomy over time and resilience to stress (Lu and Li, 2003). Heterogeneous habitats, which are characterised by species diversity and relative species and genes differentiation, are considered more resilient than homogeneous habitats (Loreau et al., 2002). Heterogeneous habitats can influence the health of urban ecosystems by contributing to their resilience, organisation, and vigour (Tzoulas et al., 2007). Biodiversity and ecosystem health are the key elements for the implementation of ecosystem services at every scale (Vergnes et al., 2013).

GBI may provide the physical basis for ecological networks. Ecological and habitat corridors, in particular, are considered as landscape elements, which can counteract the negative effects of habitat fragmentation. Many countries have developed their own legal definitions of corridor, emphasising different objectives and approaches to biodiversity conservation (Jongman et al., 2004) and identifying landscape management policies to protect and develop corridors within green frameworks from local to regional scales (Bryant, 2006; EEA, 2012; Jongman et al., 2004; Vergnes et al., 2013).

Ecological corridors usually have a linear structure – as they can be found on linear pieces of land, which are different from the surrounded matrix (Forman, 1995) – where plants and animals can travel from one area to another, increasing the movement of organisms among patches in fragmented landscapes or among landscape elements in a mosaic of habitat types (Hess and Fischer, 2001; Bailey, 2007; Gilbert‐Norton et al., 2010; Vergnes et al., 2013; Figure 6.2). The restoration of natural riparian systems and wetlands found in river and stream corridors is one of the best practices t...