Green Infrastructure Audit

Photograph by Takashi Hososhima

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Contents 1

INTRODUCTION

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THE CONTEXT

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DETAILED AUDIT FINDINGS

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PROPOSED GREEN INFRASTRUCTURE

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List of figures Figure 1.1: Figure 1.2: Figure 1.3: Figure 1.4: Figure 1.5: Figure 1.6:

Map of site and its existing land uses.

Map of existing terrestrial GI sites.

Map of potential terrestrial GI sites.

Map of existing street trees.

Map of existing green roofs and potential green roof ratings.

Map of proposed sites for greening.

List of tables Table 1.1: Table 1.2: Table 1.3:

Potential rainfall attenuation through extensive green roofs.

Potential rainfall attenuation through semi-intensive green roofs.

Potential rainfall attenuation through intensive green roofs.

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1 Introduction Scope of the study 1.1 Green Infrastructure (GI) in this audit refers to natural components of a landscape and include on the following: • Parks and other public green spaces.

• Private spaces e.g. domestic gardens.

• Green roofs.

• Street trees.

• Green corridors e.g. road corridors and rights of way.

GI provides many benefits to the environment which include increasing the biodiversity of a given space, recreation provisions, helping with flood alleviation, climate adaptation and visually improve a site.

1.2 This audit focuses on the Central and North campuses of the University of Sheffield. This part of the university is just west of the heart of the city and therefore highly developed and densely built up with few areas of open and green spaces (figure 1.1).

1.3 The University of Sheffield is currently in the process of creating their own Biodiversity Action Plan (BAP) to compliment that of Sheffield’s Biodiversity Habitat Action Plan (HBAP) of which they are partners. Through the BAP they aim to identify opportunities within the campus to enhance biodiversity or to introduce it, promising to deliver a number of targets within the HAP and thus creating a positive image of environmental awareness.

1.4 This report sets out the findings of a green infrastructure audit for the University of Sheffield Central and North campuses. The study identifies both exiting GI resources and the opportunities for retro-fitting new GI for the enhancement of biodiversity on the site. The main components this report focuses on are green and flat roofs, street trees, terrestrial green space, and rainwater attenuation which will be accurately mapped out using GIS. 1.5 At the end of the audit an assessment is made using the findings and a number of specific locations within the site for GI proposed. Discussion and guidance on whether the opportunities for enhancement and creation to improve the GI resource are feasible and how to maximise its viability are given.

Approach and method 1.6 The maps in this GI audit were constructed primarily by desk-based study using Geographical Information Systems (GIS) and aerial photography, as well as Ordnance Survey maps and existing GI maps from recent research. A ground-truthing site survey was later carried out to confirm the accuracy of the mapped data. The site survey also enabled more detailed information to be gathered on the current quality of the GI, and potential opportunities to enhance them.

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2 The Context University of Sheffield 2.1 The University of Sheffield is one of the UK’s leading universities and attracts nearly 25,000 students from 128 countries worldwide. Much of the buildings in the Central campus were built around the 1960’s and 90’s though the Information Commons (IC) was built in 2007 and the new ly refurbished Students Union opened in 2011.

2.2 The university is situated on primary circulation routes including the bus and tram network as well as a major roundabout, making the site extremely polluted and heavily congested.

Development context 2.3 Recent on site developments include a £80 million refurbishment programme of the campus including updating the Grade II listed Arts Tower Building, the construction of the IC and rebuilding the Students Unions.

2.4 The inauguration of the North campus took place only in recent years (including the Kroto Research Institute and the Nanoscience and Technology Centre) costing £20 million.

2.5 The campus now stretches over a mile long from St George’s Square to the Crookesmoor Building.

Environmental context 2.6 The site is near conservation areas including those of Broomhill, Broomhall and the City Centre.

2.7 The site is also in close proximity to major green and open space components of Sheffield’s green strategy including Weston Park, Crookes Valley Park and Ponderosa.

2.8 Flood Management – The buildings on campus show potential to be retro-fitted with new green roof systems which help to alleviate flood risks on campus by retaining water. UK Climate Impacts programme have predicted that there could be an increased level of rainfall (12-16% by 2050 and between 16-26% by 2080) so preparation for the future as well as extreme weather events is important. The way in which green roofs work is through holding the water on site and slowing rainwater run-off into drains. As well as providing this function they can also be made to look attractive to humans and to increase opportunities for wildlife and biodiversity whilst decreasing the urban heat island effect caused by dense buildings.

2.9 Open Space and Recreation – There is the potential to create more open spaces on campus to provide opportunities for biodiversity as well as places for users of the site to utilise for light recreation such as sitting, meeting or reading. This would also help improve the green image of the university.

1.10 Wildlife and Biodiversity – There is little scope to increase wildlife being such a built up area but there is great scope to increase biodiversity.

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3 Detailed Audit Findings 3.1 This section outlines the results from desk-based assessment and site audit findings.

Terrestrial GI 2.2 Existing terrestrial GI were identified by studying aerial and ordinance survey maps which were later confirmed by site survey and the results mapped in (figure 1.2). GI with potential to become part of the green network are shown in (figure 1.3). A range of opportunities were found although most are small scale due to the density of buildings on campus.

Street trees 2.3 Data of existing street trees carried out recently by postgraduate research students were made available through the university’s online learning environment and used in this audit. The resulting map is shown in (figure 1.4).

Flat and green roofs 2.4 Flat and green roofs were identified using a mixture of aerial maps and site surveying from locations which gave a bird’s eye view of the campus.

Green roof ratings 2.5 Each roof has been scored according to the below green roof rating system and the results can be found in (figure 1.5).

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Rainfall attenuation 1.1 Sheffield can expect around 5-6 days of thunderstorms each year which are most frequent from May to September, reaching their peak in July and August.

An example of an especially serious thunderstorm was in 15-16 July 1973 when Sheffield and surrounding areas received over 100 mm in a few hours.

1.2 The campus has potential to create up to 20649m² of green roofs for rainfall attenuation.

1.3 Using the broad assumptions that: • An extensive green roof will attenuate between 45-55% of annual rainfall.

• A semi-intensive green roof will attenuate between 60-65% of annual rainfall.

• An intensive green roof will attenuate between 90-100% of annual rainfall.

1.4 And that annual precipitation in Sheffield is approximately 824mm and days of rainfall ≥ 1mm is 131.2 days; the potential attenuate rainfall on campus through the installation of greens at the proposed locations has been calculated and set out below in (tables 1.1, 1.2 and 1.3).

Table 1.1: Potential for rainfall attenuation through extensive green roofs

Number of roofs

Total area (sq m)

Rainfall attenuation at 45% (m³)

Suitability for delivery of a green roof

Suitable for extensive

*

Yes

1

114

51.3

62.7

**

Yes

4

1780

801

979

***

Yes

8

5401

2430.45

2970.55

****

Yes

7

5827

2622.15

3204.85

*****

Yes

2

3000

1350

1650

Existing

Yes

8

4527

2037.15

2489.85

30

20649

9292.05

11356.95

TOTAL

Rainfall attenuation at 55% (m³)

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Table 1.2: Potential for rainfall attenuation through semi-intensive green roofs

Number of roofs

Total area (sq m)

Rainfall attenuation at 60% (m³)

Suitability for delivery of a green roof

Suitable for semi-intensive

**

Yes

4

1780

1068

1157

***

Yes

8

5401

3240.6

3510.65

****

Yes

7

5827

3496.2

3787.55

*****

Yes

2

3000

1800

1950

21

16008

9604.8

10405.2

TOTAL

Rainfall attenuation at 65% (m³)

Table 1.3: Potential for rainfall attenuation through intensive green roofs

Number of roofs

Total area (sq m)

Rainfall attenuation at 90% (m³)

Suitability for delivery of a green roof

Suitable for intensive

****

Yes

7

5827

5244.3

5827

*****

Yes

2

3000

2700

3000

9

8827

7944.3

8827

TOTAL

Rainfall attenuation at 100% (m³)

1.5 This demonstrates that if all green roof opportunities were delivered that: • 30 extensive green roofs could attenuate up to 11,357 m³ of rainfall.

• 21 semi-intensive green roofs could attenuate up to 10405.2 m³ of rainfall.

• 9 intensive green roofs could attenuate up to 8827 m³ of rainfall.

4 Proposed Green Infrastructures 2.1 Many opportunities for potential green infrastructure have been identified though the study. 5 sites shown on map (figure 1.6) have been identified as examples of feasibility in delivering GI in the area and how to maximise the functions these GI deliver.

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