Regulating urban surface runoff through nature-based solutions – An assessment at the micro-scale. Zölch,T, Henze, L, Keilholz, P & Pauleit, S. Environmental Research, Volume 157, August 2017, Pages 135–14.
- Runoff after heavy rain events accounts for approx. 95% of total precipitation in highly sealed urban areas.
- By enhancing water storage capacities green infrastructure reduces runoff by max. 14.8% compared to the baseline.
- Green roofs and trees both show to be effective but due to different functions.
- The reduction of runoff is larger with higher shares of green cover in the case area.
Urban development leads to changes of surface cover that disrupt the hydrological cycle in cities. In particular, impermeable surfaces and the removal of vegetation reduce the ability to intercept, store and infiltrate rainwater. Consequently, the volume of stormwater runoff and the risk of local flooding rises. This is further amplified by the anticipated effects of climate change leading to an increased frequency and intensity of heavy rain events. Hence, urban adaptation strategies are required to mitigate those impacts.
A nature-based solution, more and more promoted in politics and academia, is urban green infrastructure as it contributes to the resilience of urban ecosystems by providing services to maintain or restore hydrological functions. However, this poses a challenge to urban planners in deciding upon effective adaptation measures as they often lack information on the performance of green infrastructure to moderate surface runoff. It remains unclear what type of green infrastructure (e.g. trees, green roofs), offers the highest potential to reduce discharge volumes and to what extent.
Against this background, this study provides an approach to gather quantitative evidence on green infrastructure’s regulation potential. We use a micro-scale scenario modelling approach of different variations of green cover under current and future climatic conditions. The scenarios are modelled with MIKE SHE, an integrated hydrological modelling system for building and simulating surface water and groundwater flow, and applied to a high density residential area of perimeter blocks in Munich, Germany. The results reveal that both trees and green roofs increase water storage capacities and hence reduce surface runoff, although the main contribution of trees lies in increasing interception and evapotranspiration, whereas green roofs allow for more retention through water storage in their substrate. With increasing precipitation intensities as projected under climate change their regulating potential decreases due to limited water storage capacities. The performance of both types stays limited to a maximum reduction of 2.4% compared to the baseline scenario, unless the coverage of vegetation and permeable surfaces is significantly increased as a 14.8% reduction is achieved by greening all roof surfaces.
The authors conclude that the study provides empirical support for the effectiveness of urban green infrastructure as nature-based solution to stormwater regulation and assists planners and operators of sewage systems in selecting the most effective measures for implementation and estimation of their effects.
Urban green infrastructure as nature-based solution to regulate surface runoff becomes increasingly important, as climate change and urbanisation alter the urban water balance. The present study assessed the performance of two urban green infrastructure (UGI) types, trees and green roofs, on relevant hydrological processes, especially surface runoff. The two measures were applied in scenarios of different greening quantity and for heavy rain events of different intensities as projected for the future. This scenario approach revealed that both trees and green roofs contribute positively by interception, evapotranspiration and infiltration. Differences in their performance showed to be dependent on the greening quantity, share of permeable surfaces leaf area index (LAI) and finally, intensity of the rainfall event. Generally, their effectiveness remains low under heavy rain events, unless a significant proportion of the case area is greened to provide sufficient water storage capacities (Artmann, 2014).
For urban planning the presented results have practical implications for the selection of UGI types to reduce surface runoff volumes and in consequence reduce discharge loads, the sewage system has to handle. An effective nature-based solution increases the storage capacities within the area of interest as much as possible, while using open spaces that have not been used previously and/or while providing benefits to other areas of urban planning. Trees increase the storage capacity mainly by intercepting and evapotranspiring rainwater, their infiltration capacity is limited to the tree pits. But trees can normally not be implemented in large quantity in dense urban areas due to their requirements of open space. Green roofs on the other hand, provide storage capacity mainly by retaining rainwater in their substrates and can be implemented at larger scale on previously unused roof surfaces.
Furthermore, both types are multifunctional and can provide co-benefits for urban planning. The approach represents a first step in allowing planners as well as operators of sewage systems to estimate reductions in runoff volume when locally implementing UGI measures. These estimations could be further improved by integrating additional stormwater management practices and the drainage system in more detail into the modelling setup. Thus, conducting a larger systematic study of UGI scenarios would allow for including e.g. more UGI types, different species and LAI values as well as planting conditions. Such a study could enhance the provision of empirical evidence for climate resilient urban planning.
In March 2013 the Landscape Institute published an updated Mission Statement, ‘Green Infrastructure: An integrated approach to land management’. The document was described as,
“An opportunity to showcase a range of successful strategic GI work and completed
projects. The aim is to give public and private sector bodies, clients and natural and built environment professionals fresh insights into the benefits GI can bring by creating multifunctional landscapes and show how people can collaborate to deliver it.”
Research: Collentine, D. & Futter, M.N. (2016). Realising the potential of natural water retention measures in catchment flood management: trade-offs and matching interests. Journal of Flood Risk Management. DOI: 10.1111/jfr3.12269.
Natural water-retention measures, which ‘keep the rain where it falls’, have great potential to be used as part of flood-risk management plans. But their benefits for downstream urban areas can bring costs to the upstream agricultural areas where they are installed. The researchers suggest that we need new and/or improved policies and institutions to oversee the trade-offs and benefits for agriculture and flood management, and a better scientific understanding of the measures’ likely impact on urban flood risk.
The analysis, conducted by academics in Sweden, draws on various studies to discuss the many benefits of natural water-retention measures and how to encourage their uptake. Floods, which have caused annual economic losses of €4 900 million in Europe, are a serious problem. Natural water-retention measures could play an important role in managing floods, the researchers say, and help meet the goals of the EU’s Floods Directive and Water Framework Directive. These nature-based solutions store rainfall and allow it to evaporate back into the atmosphere to help prevent water flowing into urban areas, where it can cause the greatest damage.
Nature based water-retention measures are a key example of how green infrastructure can work alongside traditional grey infrastructure (e.g. flood gates). They take many forms, from small green roofs to large forests, and bring multiple benefits. As well as reducing flood risk, they can have value for biodiversity, recreation and water quality because they reduce soil erosion and can prevent agricultural pollution running into rivers.
However, this multi-functionality may also act as a barrier to their uptake. Because they bring benefits that fall under different policy areas, it is not necessarily easy for decision makers to determine who should pay for these measures. For some measures, the effect on flood risk may be an additional, secondary benefit — as in the case of agricultural buffer zones, which are primarily intended to reduce fertiliser run-off.
Alongside flood-management benefits, measures installed on upstream agricultural land can also lead to trade-offs, notably reduced crop yield. This loss occurs either because cropland is replaced by the measures or because soil in fields becomes too wet. A payment-for-ecosystem-services (PES) model could, therefore, be used to finance natural water-retention measures, possibly through national agri-environmental schemes. Research from the USA has indicated that it is less costly to pay farmers to temporarily flood their land upstream, than it is to pay for urban damage downstream.
Other barriers to widespread uptake of natural water-retention measures include specific knowledge gaps. There is plenty of evidence to show the effectiveness of individual natural water-retention measures, particularly in small catchments. Computer-modelling studies suggest natural water-retention measures could contribute to downstream flood risk reduction, but there is a lack of real world studies which show how to incorporate such measures into flood-risk management plans and their likely impact on downstream urban flood risk. Such studies are needed to encourage further uptake by decision makers and land managers.
The exact area of responsibility of decision makers with regard to flood-risk management also remains unclear. As such, water policy at the national level is accountable to EU water directives and national decisions must be consistent with the decisions made at the EU level. This is also true for regional-level policy, which is based on national policy and, similarly, local decisions are founded on regional policy. Unfortunately, this set of embedded decisions seems to break down with flood-risk management and has led to a lack of distinction between jurisdictions. Each jurisdiction attempts to reduce flood damage within a limited area and thus tends to focus on the use of preventive structural measures, such as dams or retaining walls, rather than measures to reduce flooding (1).
The authors recommend that institutional structures and mechanisms are created or enhanced to oversee the urban/rural trade-offs that natural water-retention measures may bring, to match potential costs with benefits and ensure an appropriate compensation scheme is put in place; for example, one which links PES with flood-risk management plans.
1. This shortcoming should normally be addressed by the inclusion of a river basin approach within the flood risk management plans: http://ec.europa.eu/environment/water/index_en.htm
A new framework has been developed to assess how effective Flood Emergency Management Systems (FEMS) are in Europe. Examining FEMS in five European countries, this study highlights the strengths and weaknesses of existing systems and makes recommendations for improving their effectiveness, particularly in relation to institutional learning, community preparedness and recovery.
Source: Gilissen, H. K., Alexander, M., Matczak, P., Pettersson, M. & Bruzzone, S. (2016). A framework for evaluating the effectiveness of flood emergency management systems in Europe. Ecology and Society, 21(4):27. DOI: 10.5751/ES-08723-210427. This study is free to view at: www.ecologyandsociety.org/vol21/iss4/art27/
Climate change is expected to increase the frequency and severity of floods and society must be able to respond to this evolving threat. To achieve this, FEMS, which are designed to ensure that emergency professionals are prepared for floods, should include assessments of risk to underscore flood-specific emergency planning, promote inter-agency working, professional training, facilitate community preparedness and support immediate recovery activities, such as restoring essential services and supplies. Whilst FEMS are embedded within broader legal and policy frameworks for integrated emergency management and civil contingencies, the pressing challenges posed by floods provide a strong case for examining FEMS in isolation.
This study, partly conducted under the EU STAR–FLOOD [see reference below] project, presents a new framework to assess and monitor the effectiveness of FEMS in European countries from legal and public-administration perspectives. To build the framework, the researchers conducted an appraisal of existing international academic and grey literature published since 1970, relating to emergency and disaster-management systems for any type of hazard at international, national and subnational levels. This informed the identification of seven key indicators that could be used to evaluate the performance of processes and actions in emergency flood management:
- Planning: development of an emergency plan to establish priorities, actions and decision-making in the event of a flood emergency;
- Institutional learning: procedures to be in place to promote learning at frequent intervals (e.g. post-event reviews and inquiries, opportunities for knowledge exchange across responding agencies);
- Exercising emergency arrangements: planning and operational procedures should be tested at multiple scales;
- Joined-up working: distribution of responsibilities within and between emergency actors must be clearly defined, effectively coordinated and collaborative;
- Community preparedness: should be supported by emergency professionals (e.g. raising risk awareness and direction on what to do when a flood occurs);
- Provision of resources: (financial, human resources, equipment, and decision-support tools) needs to be ensured and arrangements need to be established for sourcing and allocating additional resources as required;
- Recovery-based activities: arrangements should be in place to support evacuation, for temporary housing, restoration of essential services, help for businesses to function, dealing with physical damage and management of environmental impacts, such as pollution and contamination.
To put this framework into use, the researchers outlined key benchmarks against which a country’s performance can be scored; for this, they used a scale of one to five (absent/minimal, emerging, moderate, significant and outstanding).
The researchers then collected information from a variety of sources to evaluate the extent to which benchmarks are achieved in five European countries: France, the Netherlands, Poland, Sweden and the UK (specifically England). The information was drawn from the analysis of emergency-management policy documents and legislation, as well as stakeholder interviews and workshops with key practitioners and policymakers involved in emergency management and flood-risk management more broadly (for example, government departments, municipal and local authorities, and emergency responders).
The National Flood Emergency Framework for England (December 2014) sets out the government’s strategic approach to achieving the aims set out below and is intended for use by all those involved in planning for and responding to flooding from:
- the sea
- surface water
- groundwater and
The concept of a National Flood Emergency Framework was promoted by Sir Michael Pitt in his report on the summer 2007 floods. Its purpose is to provide a forward looking policy framework for flood emergency planning and response. It brings together information, guidance and key policies and is a resource for all involved in flood emergency planning at national, regional and local levels. It is a common and strategic reference point for flood planning and response for all tiers of government and for responder organisations.
More precisely, the purpose of the Framework is to:
- ensure delivery bodies understand their respective roles and responsibilities
- give all players in an emergency flooding situation a common point of reference – bringing together information, guidance and key policies in a single planning document
- establish clear thresholds for emergency response arrangements
- place proper emphasis on the multi-agency approach to managing flooding events
- provide clarity on the means of improving resilience and minimising the impact of flooding events
- provide a basis for individual responders to develop and review their own plans and
- be a long-term asset that will provide the basis for continuous improvement in flood emergency management
Responding to floods in Europe: new framework assesses effectiveness of Flood Emergency Management Systems
Of the five countries, England’s FEMS were found to be the most effective, with all seven indicators achieving significant or outstanding ratings. In the absence of statutory rights to flood protection, a diversified approach to FEMS has existed for over 65 years in England; thus, flood emergency management has served as a crucial strategy for minimising the consequences of flood events. Dedicated policy for flood emergency management is seen, with multi-agency flood plans as a standard component of common practice. Moreover, formal legal mechanisms underpin effective integrated working between emergency responders (e.g. duties to cooperate, and formation of Local Resilience Forums) and certain responders are actively involved in activities to enhance community preparedness for floods.
In Sweden, given the low distribution of flood risk, flood protection management is organised at the local or municipal level on a relatively ad hoc basis by those municipalities affected by flooding, rather than being established at the national scale. Whilst this is considered to be an efficient strategy and provides the necessary flexibility for municipalities to adapt to local risks, there is a risk that some areas may be neglected. Moreover, the lack of national arrangements and supportive mechanisms may make it difficult for certain municipalities to mobilise the necessary resources, according to the researchers.
In France, emergency management has evolved over the past few decades and has been integrated into local disaster-management planning and policies, in line with broader initiatives towards decentralised governance. ‘Professionalisation’ of the public is one of the major aims of the French FEMS, where voluntary fire brigades play a key role. Municipalities can optionally call in voluntary civil-protection reserves to assist in response activities. Efforts to enhance community preparedness are becoming nationally more consistent. However, recovery guidance and regulation varies regionally and this is an area for improvement identified by the researchers.
In the Netherlands, historically, there has been a strong tradition of flood defence and protection, with a statutory right to be protected by the state from floods. Nonetheless, recent efforts have sought to diversify the range of strategies implemented, in order to manage flood risk more holistically and address the country’s increased vulnerability to flooding under climate change. However, certain aspects of flood emergency management (i.e., institutional learning, community engagement, and recovery) are less well developed. Moreover, the organisational structure requires some improvement, the researchers say.
In contrast to the other countries, the FEMS in Poland is still emerging in several aspects, particularly with regard to institutional learning, community preparedness and recovery-based activities. The occurrence of significant flood events (1997) has prompted establishment of the crisis-management institutional framework and efforts to improve the effectiveness of FEMS, yet gaps are seen between policy and practice. The researchers identify small-scale examples of good practice, such as the ‘flood leaders’ initiative in Wroclaw, but say these are yet to be scaled-up and implemented nationwide.
Although the researchers found that all countries had different approaches to flood-risk management, shaped by diverse political and administrative cultures and socio-economic conditions, they have produced some common recommendations to improve the effectiveness of FEMS:
- Specific provisions for flood emergency management could prove beneficial in countries where flood risk is projected to increase. Lessons could be learned from the multi-agency flood-planning groups and subgroups within Local Resilience Forums, as seen in England, which provide further clarity on roles and responsibilities at times of flood emergencies;
- National guidance could be provided for flooding in countries with a low risk of flooding, or where flood-risk areas are widely distributed, to help deliver consistent support and establish good practice at the local level;
- Specific training for flood emergencies is necessary to test planning, responsive procedures and communication systems, as well as helping to raise community awareness of flood risks;
- Efforts to encourage community preparedness require better communication of flood risks and need to be situated alongside wider efforts to normalise adaptation within society.
- STAR-FLOOD (STrengthening And Redesigning European FLOOD risk practices Towards appropriate and resilient flood risk governance arrangements) was supported by the European Commission under the Seventh Framework Programme. http://cordis.europa.eu/result/rcn/153561_en.html
- Water Square Benthemplein, design 2011-2012, completed 2013
- Rotterdam, NL
- Rotterdam Climate Initiative, City of Rotterdam supported by the Waterboard Schieland & Krimpenerwaard
- Final design, built
- City of Rotterdam Engineering Bureau. Baptistry: Anouk Vogel. Color advice: Annet Posthumus. Social feedback: Arnold Reijndorp & Machiel van Dorst. Construction/coordination and concrete works: Wallaard. Steel gutters: ACO
Urban flood resilience in Rotterdam – the Benthemplein Water Plaza, the first large-scale multifunctional water plaza in the world. Visitors can sit and relax, play sports or skateboard in the sunken interior, which also doubles as flood storage, collecting runoff from the surrounding streets and discharging it back into the system when drier weather resumes.
The water square combines water storage with the improvement of the quality of urban public space. The water square can be understood as a twofold strategy. It makes money invested in water storage facilities visible and enjoyable plus generates opportunities to create environmental quality and identity to central spaces in neighborhoods.
Most of the time the water square will be dry and in use as a recreational space. The exemplary design for the watersquare is divided into two main parts: a sports area and a hilly playground. The space is captured by a green frame of grass and trees. When heavy rains occur, rainwater that is collected from the neighborhood will flow visibly and audibly into the water square. Short cloudbursts will only fill parts of the square. When the rain continues, more and more parts of the water square will gradually be filled with water. The rainwater is filtered before running into the square.
The rainwater will be held in the square until the water system in the city has enough capacity again. Then the water can run off to the nearest open water. The water square is therefore also a measure to improve the quality of the open water in urban environments. After it has been in use as buffering space, the water square is cleaned. Therefore the design is made with fluent slopes.
A typological research and design on water squares was carried out in 2006-2007. The water square became official policy on an urban scale in the “Rotterdam Waterplan 2” in 2007. A pilot study was carried out in 2008-2009. In 2010 the graphic novel “De Urbanisten and the Wondrous Water square” was published by 010, Rotterdam. The Rotterdam Waterplan 2 stated that,
Rotterdam is working on a strong economy and an attractive residential environment. Water is an important aspect of an attractive city, certainly one that profiles itself as ‘water city’. The vision of Rotterdam for the future plays an important role in all the plans. In addition, there are three crucial developments with which we will, or might be, faced in the period ahead:
- Higher water level due to the rise in sea level. There is a risk of flooding in areas outside the dykes. Flood defences will simply have to be reinforced.
- Flooding caused by increasing rainfall. Due to the changing climate, a lot of rain can fall in a short space of time. In order to process that water, provisions are needed for collection and storage. At the moment, there is already a shortage of around 600,000 m3 of storage. At least 80 hectares of extra lakes and canals would be needed to cope with this shortage by means of open water.
- Stringent demands on the quality of water. Rotterdam wants to be an attractive water city, with clean, clear and plant-rich water. The city must also meet European requirements (the European Framework Directive on Water). So-called quality profiles, based on these requirements, are in the process of being drawn up for all stretches of water in the city.
The masterplan document sets out ‘decisions of crucial importance’ to tackle the above problems citing the attractiveness of Rotterdam as perhaps the most important decision: how can the city be made even more attractive as a place to live, work, study and spend leisure time, and can the water problems be solved at the same time? In the city centre and the old neighbourhoods, for example, it isn’t possible to tackle the problems of water storage by digging extra facilities. The costs are exorbitant and existing buildings can’t simply be demolished. Innovations such as green roofs, ‘water squares’, alternative forms of water storage and the like are therefore essential for the further development of the city.
In his paper, ‘Constructing Landscape by Engineering Water’, Antoine Picon states that, “Technology used to be defined as an action exerted by man on nature. Nowadays we may wonder, especially in the urban context, whether man is adapting the very concept of nature to cope with the challenges we face.”
Picon, Professor of the History of Architecture and Technology at the Harvard Graduate School of Design, refers to “techno-nature”, a phrase he uses to describe the blurring between nature and the modern day, man-made urban realm. He claims that this is most prominent in the design of remedial landscapes . Historically, engineered hydraulic designs made clear distinctions between natural and man-made interventions – canals, aqua-ducts, locks and water treatment and storage was visibly constructed and segregated. Nowadays however, projects are often a combination of hard and natural engineering with a stronger reliance on nature based solutions for water management.
“Blending the natural and the artificial is not easy to reconcile with the public’s desire for close contact with natural elements and ambiances. Part of the challenge for landscape designers is to propose sequence that function with a harmonious combination of natural appearances and unavoidable artificiality.” Antoine Picon, ‘Constructing Landscape by Engineering Water’
Source: Institute for Landscape Architecture, ETH Zurich (ed.), Landscape Architecture in Mutation: Essays on Urban Landscapes, Zurich: gta Verlag, 2005, pp. 99-115.
Such as the project on the banks of the River Seille at Metz, France. Here everything is artificial – the project focuses on the development of a new water catchment basin created by a new branch of the river – ‘giving the Seille River an extra arm’ – to assist regulating the Seille River’s hydrography. The project provides a new ‘natural element’ on the edge of the city.
Parc de La Seille – METZ (Moselle)
Completion year 2003
Contracting Authority Municipality of Metz
Mission Creating an urban park featuring an advanced environmental approach
Project Management Team Landscape architects and designers Jacques Coulon (mandated agent), Landscape architects and designers Laure Planchais, Ecological engineers Sinbio, Civil works engineers Ingerop, Light designers Coup d’Eclat
Surface area 20 hectares (excluding the Seille River)
Budget €6m exc. VAT
Ratio €30 exc. VAT per m²
The Parc de La Seille was intended to be a space widely open to the skies, highlighting the topographical features of the banks of the river that runs through it by forming links with the surrounding existing and future urban landscape. Significant levelling has been performed to open up the Seille River which had until then been channelled, as well as shaping the hills that link the park to the future slab-mounted Amphitheatre district. A vast prairie stretches at the foot of the hills, which is used to host various activities.
The park has a number of purposes:
- “Reclaiming” the riverside environment
- Regulating the Seille River’s hydrography
- Collecting water for the future Amphitheatre district
- Forming a key area in the city, suitable for hosting sports and cultural events.
By increasing the areas liable to flooding, and giving the Seille River an extra arm, the park solves all hydrological issues and gains an alluvial setting. The water gardens provide a contrast with the dry hill gardens, encouraging some diversification among the possible biotopes in the area.
As a more urban feature, the esplanade hosts those sports and cultural events that are more spectacular. It starts out inside the Amphitheatre district by the Metz Centre Pompidou, and ends up as a platform overlooking the Seille River, thereby accentuating the bond between the district and the river.
Over 20 hectares, the park offers areas of flowering plants, wet and dry meadows, vineyards and hop growing on hillside, fruit trees and others, sports and play areas plus many trails.
A Resilient Landscape: Yanweizhou Park in Jinhua City – Kongjian Yu, Peking University College of Architecture and Landscape, and Turenscape
- Location: Jinhua City, Zhejiang Province, China.
- Size: 26 Hectares
- Client: Jinhua Municipal Government
- Design Firm: Turenscape
- Design Team: Kongjian Yu (design principal), Hongqian Yu, Yu Song, Yuan Fang, Shuiming zhou, hui Tong, Shenghui Li, Chujie Lin, Dengfeng Chen
- Completed: 2014
The Yanweizhou Park, Jinhua City project by turenscape landscape architectures, is a finalist for Rosa Barba Prize and was presented at the International Biennial of Landscape Architecture in Barcelona on September, 2016. Turenscape also designed Qunli Stormwater Park: Heilongjiang Province, China
Site and Challenges
In Jinhua, a city with a population of over one million, one last piece of natural riparian wetland of more than 64.acres remained undeveloped. It is located at the juncture of the Wuyi and Yiwu Rivers to form the Jinhua River, now the site of the Yanweizhou Park.
Before the Yanweizhou Park project was implemented, the three rivers, each of which is over 100 meters wide, divided the densely populated communities in the region. As a result of this, the cultural facilities, including the opera house and the green spaces adjacent to the Yanweizhou were underutilized. The remaining 50-acre riparian wetland was fragmented or destroyed by sand quarries. The existing wetland is covered with secondary growth dominated by poplar trees (Populus Canadensis) and Chinese Wingnut (Pterocarya stenoptera) that provide habitat for native birds.
4 major challenges to the landscape architect:
- Can the remaining riparian habitat be preserved while providing amenities to the residents of the dense urban center?
- What approach to flood control should be used (prevention with a high, concrete retaining wall or cooperation by allowing the park to flood)?
- Can the existing organically shaped building be integrated into the surrounding environment to create a cohesive landscape that provides a unique experience for visitors?
- Can the separated city districts be connected to the natural riparian landscape to strengthen the community and cultural identity of the city of Jinhua?
Fig 1. Aerial view of the park during the monsoon season with uninterrupted connection of the city through the bridge
Fig 2. Aerial view of the park during the dry season, with lush tall grasses covering the terraces on the embankment. The terraces are enriched by silt deposited during the flood season
Design Strategies: Resilient Landscape
- Adaptive Tactics to Preserve and Enhance the Remnant Habitats
The first adaptive strategy was to make full use of the existing riparian sand quarries with minimum intervention. In this way, the existing micro-terrain and natural vegetation are preserved, allowing diverse habitats to evolve through time. The biodiversity of the area was adapted and enhanced through the addition of native wetland species. This enrichment, particularly of species that provide food for birds and other wildlife, increases biodiversity.
- Water Resilient Terrain and Planting Design
Due to its monsoon climate, Jinhua suffers from annual flooding. For a long time, the strategy to control flooding was to build stronger and taller concrete floodwalls to yield cheap land for urban development. These walls along the riverbanks and riparian flood plains severed the intimate relationship between the city, the vegetation, and the water, while ultimately exacerbating the destructive force of the annual floods.
Following this formula, hard high walls have been built, or were planned to be built, to protect the last patch of riparian wetland from the 20-year and 50-year floods. These floodwalls would create dry parkland above the water, but destroy the lush and dynamic wetland ecosystem. Therefore, the landscape architect devised a contrasting solution, and convinced the city authority to stop the construction of the concrete floodwall and to demolish others. Instead, the Yanweizhou project “makes friends” with flooding by using a cut-and-fill strategy to balance earthwork and by creating a water-resilient terraced river embankment that is covered with flood adapted native vegetation. Floodable pedestrian paths and pavilions are integrated with the planting terraces, which will be closed to the public during the short period of flooding. The floods bring fertile silt that is deposited over the terraces and enrich the growing condition for the tall grasses that are native to the riparian habitat. Therefore, no irrigation or fertilization is required at any time of the year. The terraced embankment will also remediate and filtrate the storm water from the pavement above. Although the design and strategies employed address only a small section compared to the hundreds of kilometers of river embankment, the Yanweizhou Park project showcases a replicable and resilient ecological solution to large-scale flood management.
Fig 3. Terraced embankments were built by removing the concrete floodwall and through a cut-and-fill strategy that balances the earthwork on-site. The terraces create a flood resilient zone that allows people to enjoy the lush tall grasses adaptive to the seasonal floods
In addition to the terraced river embankment, the inland area is entirely permeable in order to create a water resilient landscape through the extensive use of gravel that is re-used material from the site. The gravel is used for the pedestrian areas, the circular bio-swales are integrated with tree planters, and permeable concrete pavement is used for vehicular access routes and parking lots. The inner pond on the inland is designed to encourage river water to infiltrate through gravel layers. This mechanically and biologically improves the water quality to make the water swimmable.
Fig 4. Inner pond is designed to allow water to infiltrate from the river through the gravel layers that make the otherwise dirty river water suitable for swimming.
- A Resilient Pedestrian Bridge Connects City and Nature, Future and Past
A pedestrian bridge snakes across the two rivers, linking the parks along the riverbanks in both the southern and northern city districts, and connecting the city with the newly constructed Yanweizhou Park within the river. The bridge design was inspired by the local tradition of dragon dancing during the Spring Festival. For this celebration many families bind their wooden benches together to create a long and colorful dragon that winds through the fields and along narrow dirt paths. Musicians sound gongs and beat drums, to the accompaniment of singing, dancing and yelling by villagers, young and old. The Bench Dragon is flexible in length and form as people join or leave the celebration. The dragon bends and twists according to the force of human flow.
As water-resilient infrastructure, the new bridge is elevated above the 200-year flood level, while the ramps connecting the riparian wetland park can be submerged during the 20-year and larger floods. Floodwaters cover the park for a very short period of time. The bridge also hovers above the preserved patch of riparian wetland and allows visitors an intimate connection to nature within the city. The many ramps to the bridge create flexible and easy access for residents from various locations of the city in adaptation to the flow of people. The landscape architect designed the bridge to reinforce the festive, vernacular tradition, but also as an art form with a bold and colorful combination of bright red and yellow tones that are strengthened by night lighting. All together 2,300’ (700 m) long, the bridge is composed of a steel structure with fiberglass handrails and bamboo paving. It is truly a resilient bridge that is adaptive to river currents and the flows of people while binding city and nature, future and past.
- Resilient Space for a Dynamic Experience
The large oval opera house (designed by the Zhejiang Architecture Institute) posed significant challenges for the landscape architect. First the building shape tends to repel rather than embrace the user and landscape. Therefore, the first challenge was devising innovative forms that would welcome and embrace the visitor. Secondly, the area near the building needed to accommodate the large opera audience as well as the need for intimate spaces and ample shade. Finally, the designers were challenged with the problem of how to integrate the singular flood-proof big object into the floodable, riparian waterfront. The design uses curves as the basic language, including the curvilinear bridge, terraces and planting beds, concentric paving bands of black and white, and meandering paths that define circular and oval planting areas and activity spaces. The spatial organization and design forms establish an extensive paved area for a large audience during the events at the opera house. However, the forms and the inclusion of alcoves create places for the individual, couples and small groups.
Fig 5. The surface of the inland area is hundred percent permeable. Generated from on-site materials, gravel is recycled to create pedestrian surfaces. Gravel surfaces alternate with unit pavers and permeable concrete to create a distinctive pattern. Bio-swales are integrated with tree planters, and permeable concrete pavement is used for automobile routes traffic use and parking lots.
The dynamic ground of the pavement and planting patterns define circular bio-swales and planting beds, densely planted with native trees and bamboo, bound by long benches made of fiberglass. The circular bio-swales and planting patches resemble raindrop ripples on the river. These curves and circles are the unifying pattern language that integrates the building and the environment into a harmonious whole. The reverse curves simultaneously refer to the shape and scale of the building while forming a contrasting shape that is human in scale and enclosed for more intimate gatherings. They also reflect the weaving of the dynamic fluxes of currents, people and material objects that together create a lively pleasant and functional space.
After the park opened in May 2014, an average of 40,000 visitors used the park and the bridge each day. The local media exclaimed: “the whole city is crazy about one single bridge!” And now, the Yanweizhou Park has created a new identity for the city of Jinhua.
Text and images : http://www.turenscape.com
Overview: A new Town and Country Planning Association (TCPA) report for the Joseph Rowntree Foundation (JRF) is warning that the majority of new local plans in England are failing to cut carbon emissions and to plan for the scale of severe weather predicted over future years. The report Planning for the Climate Challenge? Understanding the performance of English Local Plans, found that 70% had no carbon reduction targets or any way of monitoring their progress with carbon reduction. The study established the extent to which climate change mitigation and adaptation are reflected as priorities in local plan policy in England. Click here to download the full report.
The spatial planning system provides for the democratic regulation of the built environment in the public interest, and has the potential to make a major contribution to both reducing carbon dioxide emissions and preparing for the growing impacts of climate change.This report reveals that the planning system is failing to fulfil this potential.
Despite the increasing intensity and frequency of climate-related impacts, local plans are not delivering on the basic standards set out in national law and policy for either mitigation or adaptation. To deliver the fundamental change required, climate change must be placed front and centre of the policy priorities of the spatial planning system. Only a radical refocusing of the system will meet the challenges of climate change, now and in the future.
The study underpinning this report explored how local plans published since the National Planning Policy Framework was produced in 2012 are addressing climate change. Drawing on a sample of 64 local planning authorities in total, and based on an analysis of local planning documents, a survey of local authority planners and four more-detailed, area-based case study examinations, the study established the extent to which climate change mitigation and adaptation are reflected as priorities in local plan policy in England.
The study found that local plans in England are not dealing with carbon dioxide emissions reduction effectively, nor are they consistently delivering the adaptation actions necessary to secure the long-term social and economic resilience of local communities. There was a wide variety of practice: there were some examples of positive responses, but, taken as whole, it is clear that since 2012 climate change has been de-prioritised as a policy objective in the spatial planning system. The large-scale failure to implement the clear requirements of national planning policy is a striking finding, as is the reduced capacity of the local authority planning service and the reduced capacity of Environment Agency to support the long-term plan-making process.
There are complex reasons for this situation – ranging from perceived contradictions in national policy to political signals from Ministers in the Department for Communities and Local Government and HM Treasury about the overwhelming priority to be given to the allocation of housing land. In addition, in many cases local plans do not meet national policy requirements on climate change but are still judged sound by the Planning Inspectorate. Underlying all of this is a crisis in resources in the local planning service which inhibits effective local policy-making.
The failure to use the planning system’s capability to help mitigate and adapt to climate change is inefficient, and is likely to lead to long-term avoidable costs to the economy. Conversely, there is a real opportunity to harness the system as a key local part of the national response to climate change. Fulfilling this potential requires, above all else, a signal from national government that climate change is a primary political, legal and policy priority for the local plan process.
- Climate change has been de-prioritised as a significant local planning policy issue.
- Policy and legislation on climate change are poorly understood.
- National policy as set out in the National Planning Policy Framework and in National Planning Policy Guidance does provide for a clear approach to climate change. However, it also contains policy on viability which prevents some key actions from being delivered. In addition, changes made by subsequent amendments to energy, zero carbon and sustainable urban drainage policies have made action on many climate change responses more difficult.
- The evidence-gathering, methodologies and policy-making used to address flood risk were far more sophisticated than the equivalent for climate mitigation or any other aspect of adaptation. Local plans deal with carbon dioxide emissions reduction vaguely, often without an explicit methodology for measuring reductions.
- LPAs are failing to plan for future climate change and therefore are not planning for the adaptation measures necessary to secure long-term social and economic resilience.
- The governance of climate change issues at the local level is complex and sometimes contradictory. LPAs are not supported by a national agency to secure national carbon dioxide emissions reduction objectives, while the specific challenge of flood risk is reliant upon the support of the Environment Agency.
- Planning requirements do not apply to a wide range of land uses, which affects local responses to climate change.
- Specific approaches to dealing with climate change are still novel to many local authority planners, and access to affordable training is a major issue.
- Climate-change-related policy outlined in local plans is generally short term and not sufficiently future-facing to deal with climate risk.
- The duty to co-operate among LPAs is overwhelmingly focused upon housing growth, with little to no emphasis placed on cross-boundary climate change issues. However, strategic co-operation on issues such as evidence-gathering is a major opportunity area for climate change work.
This report recommends ten actions for national and local government that could significantly and cost effectively improve the performance of local plans in relation to climate change: