Challenges and Solutions in Urban Areas

CEH has a rapidly increasing portfolio of urban projects around the world, often working in an inter-disciplinary setting, with social scientists, economists and health experts as well as city stakeholders.

Shade from street trees in Beijing, ChinaOur urban portfolio covers projects in the following areas (links):

  1. Urban natural capital accounts
  2. Urban flood risk
  3. Urban air quality
  4. Water quality of urban lakes and rivers
  5. Impacts of urbanisation
  6. Multiple benefits of urban greenspace and bluespace

Urban green and blue space provides multiple benefits to city dwellers. These include mitigation of pressures such as air and water pollution, heat stress, noise, flooding, as well as more direct benefits resulting from access to greenspace which improves physical and mental well-being.

The science that underpins urban green- and blue-space benefits is in its infancy. Although expertise in this area is growing rapidly, there remain many scientific challenges to address. Examples of the questions that CEH is working to answer include:

  • Does heat mitigation require a minimum area of greenspace to be effective? 
  • Do parks need a minimum number of people using them before they are seen as a ‘safe’ open space for recreation?
  • How clean do urban waters need to be before they are seen as valuable by urban residents? What aspects do they see as ‘clean’ ?


1. Urban Natural Capital Accounts

CEH has worked with environmental economists (eftec) and other partners to develop the UK urban natural capital accounts, through a series of projects funded by the UK Office of National Statistics (ONS) and the Department of Environment Food and Rural Affairs (Defra)

Developing Estimates for the Valuation of Air Pollution Removal in Ecosystem Accounts

Contact: Laurence Jones


Pollution removed by urban vegetation, and resulting health benefits (Jones et al. 2019)
 

This CEH-led project developed a novel modelling approach to calculate the health benefits of air pollution removal by vegetation, to support the UK natural capital accounts. We used the atmospheric chemistry and transport model EMEP4UK to calculate how vegetation reduces the concentrations of those pollutants most harmful to human health (PM2.5, NOx, SO2, O3). We worked with environmental economists (eftec) and health economist Mike Holland at EMRC to calculate the health benefits which result from pollution removal by all UK vegetation types.

The overall value of this ecosystem service was £1.03 billion in 2015, and the value provided just by the vegetation in urban areas was £0.2 billion. Data are presented in this report to ONS, and this paper.

On-line Pollution Removal Tool

Contact: Laurence Jones

CEH has developed an on-line tool, with eftec, that allows users to calculate the benefits of new woodland (or loss of benefit from removing existing woodland) in their Local Authority.

Scoping natural capital accounts for ecosystem services in urban areas

Contact: Laurence Jones

In a scoping project for Defra, we worked with eftec and other partners to design new approaches to calculate urban natural accounts for a suite of ecosystem services. CEH led the quantification and spatial analysis, reported here. In subsequent projects, we took these ideas further for two services: noise mitigation and heat mitigation/cooling effects.

Natural capital accounts for noise mitigation in urban areas

Contact: Laurence Jones

Trees can help reduce road noise by 1-2 decibels, but only in the right locationsTrees can help reduce road noise by 1-2 decibels, but only in the right locations

We developed a new method to estimate the health benefits resulting from noise mitigation by urban trees. CEH led the method development, quantification and spatial analysis, while eftec provided the economic analysis. The value of road-noise mitigation by trees in 2015 was £61 million, reported here.

Natural capital accounts for heat mitigation in urban areas

Contact: Laurence Jones

 

We developed the methodology to calculate local cooling effects by urban woodland, grassland and water, in conjunction with eftec and Collingwood Environmental Planning Limited. CEH led the quantification and spatial analysis. The approach assesses economic losses in eleven UK city regions resulting from hot days above 28 °C, and how they are reduced by urban green and blue space, reported here.

2. Urban Flood Risk

CEH has worked on numerous projects modelling and predicting impacts of urbanisation on flood risk

AMMA2050 (www.amma2050.org)

Contact: Chris Taylor

Flooding in Ouagadougou, Burkina Faso

A DFID Future Climate For Africa (FCFA) project on understanding the effects of climate change in West Africa – with an urban case study focused on the City of Ouagadougou in Burkina Faso. The project has three main objectives:

  1. Provide expert judgement on future projections of High Impact Weather and climate which is tailored specifically to the needs of decision-makers.
  2. Create tools and methodologies for using these projections for planning within the agricultural and hydrological sectors.
  3. Demonstrate the potential for effective application of reliable 5-40 year climate projections and associated uncertainties in regional to local scale decision-making

Currently we are in the process of applying state-of-the-art convection permitting projections of extreme weather events over the city of Ouagadougou to understand the impacts on flooding. We are co-developing tools that enable regional stakeholders to adapt and plan for climate change and rapid urbanisation to reduce flood risk. Outputs are being used in local planning and regional climate change adaptation plans.

Urbanisation metrics & flood estimation, NERC/CEH

Contact: James Miller
Different densities of urban greenspace & urban morphology
Different densities of urban greenspace & urban morphology
 

CEH is undertaking novel research investigating the role of spatial land cover on storm runoff and flooding by developing and applying landscape metrics commonly employed in landscape ecology. This emerging area of research is showing the value of this approach and its potential for assessing the role of nature based solutions in mitigating urbanisation effects.

Integrating urbanisation in flood frequency methods, NERC

Contact: James Miller

 

CEH has led development of the updated industry standard rainfall-runoff model ReFH2 to incorporate the effects of urbanisation in the modelling schema and to provide more robust estimates of flood risk in urban areas. Testing shows the new methods provide more robust estimates for flood risk assessments. Reported here.

Change in urban land cover at catchment scale
Change in urban land cover at catchment scale
 

CEH has investigated methods for detecting and attribution of urbanisation effects of flood extremes using non-stationary flood-frequency models – incorporating long-term Land Use Change and high-flow data. Research has highlighted the role of urbanisation in driving higher flows, particularly in summer season, and the need for non-stationary models for assessing future flood frequency. Reported here.

Mapping urban land use change using historical data, NERC/CEH

Contact: James Miller
Testing different methods for calculating impervious area, squares are 2x2km: a) Aerial-photography derived, b) Fractional imperviousness, c) Imperviousness
Testing different methods for calculating impervious area, squares are 2x2km: a) Aerial-photography derived, b) Fractional imperviousness, c) Imperviousness
 

This INNOVATE research sought to develop new methods for mapping historical urban land use change to periods back before satellite data was available and which could be used to determine changes in imperviousness. The method utilised ordnance surveys maps and image processing to map imperviousness over a 60 year period (1960 – 2010) and compared this to available impervious maps derived from satellite imagery, reported here.

Peri-urban impacts on hydrological fluxes, NERC

Contact: James Miller

Urbanisation at catchment scale over 50 years, UK
 

The impacts of peri-urban development were investigated under a NERC funded programme on heat fluxes and urban flooding. The flood research built on innovative mapping of urban land use change and hydrological modelling. This paper showed that progressive urbanisation severely affected the timing and magnitude of urban runoff.

Change in timing of flood peak with increasing urbanisation
Change in timing of flood peak with increasing urbanisation
 
 

Urban Creep: manage future flood risk by quantifying rates of urban creep

Contact: Clare Rowland, James Miller
Calculating loss of urban greenspace in Edinburgh
Calculating loss of urban greenspace in Edinburgh
 

When gardens and other vegetated areas in existing settlements are built on or paved over, the land cover becomes more impermeable and this change is often referred to as ‘urban creep’.  Urban creep is likely to be a significant factor in future surface water flood risk. Being able to quantify the rates of urban creep is crucial to managing this risk.

As part of this project, funded by the Centre of Expertise for Water (CREW), CEH has developed a method to map changing urbanisation and identify areas of urban creep using aerial photography of Edinburgh. The results, due in late 2019, will provide the first high-resolution, city-wide estimates in Scotland. This new mapping method can be applied to other cities to assess potential impacts of urbanisation and help inform projections of future flood risk. Reported here.

LWEC report cards – urbanisation and climate change on storm runoff

Contact: James Miller

Score card for flood risk parameters
 
 

An Environment Agency project for the Living With Environmental Change (LWEC) programme investigated the evidence concerning the impacts of climate change and urbanisation on all forms of urban flooding. The findings are presented in this report and this paper.


3. Urban Air Quality

United Nations Environment Assembly (UNEA) resolution: Pilot to determine air quality drivers for Sub-Saharan Africa (AQD-Nairobi), NERC, 2016-2018

Contact: Marsailidh Twigg
Average ammonia concentrations in an informal settlement (Mukuru) in Nairobi, Kenya
Average ammonia concentrations in an informal settlement (Mukuru) in Nairobi, Kenya
 
 

CEH led this joint project with the Stockholm Environment Institute Africa Centre (SEI) and Muungano (Kenyan branch of Slum Dwellers International). The project aimed to assess the applicability of NERC developed low cost monitoring methods (DELTA and ALPHAs) for air quality integrated with mobile particulate matter (PM) sensors to gain knowledge on personal exposure to air pollution within informal settlements in Nairobi, Kenya. One of the key outputs was spatial information on ammonia as an indicator of waste management within the informal settlement.


TUPUMUE (Let’s Breathe) Newton Fund’s UK-Kenya Joint Partnership on Non-Communicable Diseases, MRC and the NSF Kenya, 2019-2021

Contact: Marsailidh Twigg

This multi partner project aims to generate new scientific knowledge about the early life course origins, burden, determinants, and prognostic significance of non-communicable lung disease in Kenya by studying the lung health of children and adolescents from two very different communities (an informal settlement and a wealthier district) of Nairobi, Kenya. CEH is involved in determining the air pollution exposure of the children from both communities, as part of the study.

Citizen science in the informal settlement in Nairobi: wearing a personal exposure backpack to measure particulate matter (PM)


4. Water Quality of Urban Lakes and Rivers

Restoring Urban Lakes for Multiple Community Benefits

Contact: Laurence Carvalho

Foams coming off Bellandur Lake, Bangalore, and sampling methane levels in the lake.
 

Lakes are highly valued by urban communities for multiple benefits.  However, they are highly vulnerable to pollution from wastewater and urban run-off, especially in rapidly growing cities where wastewater treatment infrastructure does not keep pace with the growth of the city. CEH are working on a case-study in Bangalore, India, to highlight the multiple benefits of restoring urban lakes. The largest in the city, Bellandur Lake, has become internationally notorious for catching fire and huge foams, becoming a hazard to communities.

Working with ATREE, we are supporting community-based initiatives to monitor water quality and ecological health, evaluate benefits and implement decentralised solutions to rejuvenate the lakes.

Water supply, water quality and infrastructure, India

Contact: Gwyn Rees

As part of a 3-year, £2M Newton-Bhabha Fund Project (2016-19), CEH, along with BGS, IISc and ATREE, investigated the effects of Bangalore’s water supply and sewerage networks and its urban lakes on the local water balance and the availability of water resources in the Cauvery River basin. The project showed that leakage from pipes, sewers and drains is by far the largest contribution to groundwater recharge within the city limits but that the water is often of poor quality.

Urban storm water channel, Bangalore
 

Urbanisation effects on water quality and quantity from local to regional scale (POLLCURB)

Contact: Michael Hutchins

This CEH-led project on the River Thames focused on urbanisation, population growth and climate change impacts on water resources. Revealing that recent urban expansion is likely to give way to densification, research suggested that hydro-climatic drivers are likely to swamp any signals of a more-extreme flow regime resulting from urbanisation. Downstream of urban areas, short-lived water quality problems result from flushing of accumulated sediment with chronic impacts arising from wastewater overspills.

A UK urban river environment vulnerable to extreme flow and poor water quality

We identified long-term trends in river flows and water quality downstream of urban areas; detection and attribution of change was undertaken in this paper.  Continuous monitoring during extreme winter stormflow in medium-sized urbanising catchments revealed a river water quality response along an urban-rural gradient. Wastewater effluent was the key driver of downstream water quality and storms actually yield some benefits by flushing catchments and recharging aquifers, reported in this paper. This study showed how use of big data has allowed increasingly integrated assessments of urban water systems.

This paper shows how changes in water demand brought about by population growth have disproportionate effects at low flows. These may result in increased incidence of very low dissolved oxygen concentrations which damage the health of the ecosystem.


Phosphate loads (x axis) and shading (y axis) are two key stressors we can control. In a drier/warmer future dissolved oxygen stress (coloured lines: days of DO below 6 mg/L) increases with high levels of urbanisation (right panel) compared with lower levels of urbanisation (left panel).
 


5. Impacts of Urbanisation

Urban expansion in the Nile Delta, impacts on agriculture and soil carbon

Contact: Laurence Jones

Urban expansion in the Nile Delta, 1972 – 2017.
 

This Newton-funded project looked at how urban sprawl over 45 years has affected agricultural area and soil carbon stock in Egypt’s Nile Delta. Results are reported in this paper.


6. Multiple Benefits of Urban Greenspace & Bluespace

CEH is working in cities in the UK, Europe and China to develop Nature Based Solutions for urban challenges.

REGREEN project on Sustainable Urbanisation

Contact: Laurence Jones

EU H2020. China – UK – Denmark – France – Croatia.
The project brings together businesses, city authorities and researchers to inform and design Nature Based Solutions, focusing on key pressures in six European and Chinese cities, ‘Urban Living Labs’: Beijing, Shanghai, Ningbo, Paris, Aarhus, Velica Gorica. CEH leads a work stream on Quantifying Challenges, and has a major contribution to modelling urban ecosystem services, and integrated assessment of Nature Based Solutions.

DESCIPHER project on Sponge Cities

Contact: Michael Hutchins

Designing Sponge Cities for multiple benefits: integrating nature based solutions to create sustainable places - through Innovation, Policy, Health and Environmental Research), ESRC – NSFC funded, China – UK – Norway, 2019-2022
The project will design Nature Based Solutions for liveable cities, extending the Sponge Cities concept to air pollution removal and other co-benefits of urban green and blue space. It will assess biophysical and societal benefits at multiple scales, including peri-urban. Outputs will include a decision-support tool.

Making a case for Greenspace

Contact: Laurence Jones

Rwanda – Malawi – Colombia – Bangladesh – UK
In this multi-partner project, IRDF funded with Leicester University, we conducted a rapid assessment of urban green and blue space benefits in five cities across four continents: Kigali (Rwanda), Zomba (Malawi), Dhaka City (Bangladesh), Medellin (Colombia), Leicester (UK).

We first calculated the urban footprint and mapped green and blue space using satellite data. A range of CEH and other tools were used to calculate the following benefits: Access to Greenspace, air pollution removal, heat mitigation, flooding mitigation. Outputs include a ‘mini-Prospectus’ outlining the benefits for each city.


Mapping urban green and blue space in Kigali, Rwanda