dissertation presentation_ suds inner london

SuDS in Inner London

Their effect on surface runoff and opportunities for effective

use.

By: Cristobal Sapena LafuenteSupervisor: James Shucksmith

Why London?

http://www.google.com/imgres?um=1&sa=N&biw=1366&bih=665&hl=es&authuser=0&tbm=isch&tbnid=tyhcZg1klcVy7M:&imgrefurl=http://www.tourist-destinations.net/2013/01/london-travel-guide.html&docid=J6v3nxqsyMYDXM&imgurl=http://3.bp.blogspot.com/-i83l-2yiFRM/UOn56uDlQZI/AAAAAAAACBA/p4qK_ees5j8/s1600/london-.jpg&w=784&h=516&ei=RwGVUc-FBMaR7AburIGYBQ&zoom=1&ved=1t:3588,r:61,s:0,i:352&iact=rc&dur=955&page=4&tbnh=178&tbnw=260&start=54&ndsp=20&tx=100&ty=94

Why London?

• Overburdened Sewer System

• Thames Tunnel Controversy

• Variety of Urban Environments

Source: Google maps

Source: Google maps

Source: Google maps

Key Questions

1- Can literature on stormwater runoff reduction be made consistent? 2- How significant would the runoff reduction be if SuDS where widespread in London?

3- Is further study needed? If so, in which areas/fields?

1-To critically appraise the published literature on SuDS runoff reduction.

2-To assess whether identifying separate urban environments aids literature appraisal.3- To obtain a general overview of the effect widespread SuDS would have on different urban environments.

Objectives

Urban Environments

Urban Environments• High population

density• Low % of open space

Tier A• Low population

density• Low % of open space

Tier B• High population

density• High % of open space

Tier C• Low population

density• High % of open space

Tier D• Low population

density• Very high % of open

space

Tier ESource: Google maps

Source: Google maps

Source: Google maps

Source: Google maps

Source: Google maps

Urban Environments• 85 Wards• 22% of inner London

areaTier A

• 46 Wards• 22% of inner London

areaTier B


areaTier C


areaTier D


areaTier E

Source: Google maps

Source: Google maps

Source: Google maps

Source: Google maps

Source: Google maps

Methodology

Literature Review

Extensive SuDSCase

Studies

Tier A Tier B Tier C Tier D Tier E

Methodology

Literature Review

Extensive SuDSCase

Studies

Tier A Tier BTier C Tier D Tier E

Specific SuDSTools

Studies

Specific SuDS - Green RoofsKey Studies:

Stovin 2009: UK based extensive roof study

34% Average based of 11 events with 80mm substrate.

Mentens et al. : Compilation of German-based studies.

Extensive roofs data based of 121 annual performances.

Intensive roofs data based of 11 annual performances.

Minimum Maximum Median Average 80 mm substrate

0

10

20

30

40

50

60

70

80Green roof data selection

Mentens et al._ Inten-sive

Mentens et al._Extensive

Stovin 2009_Extensive

Substrate scenarios

Runo

ff R

educ

tion

(%)

Specific SuDS - Permeable Pavements

Key studies – Paved Surface runoff reduction

James and Thompson (1997): 39-62%

Pratt et al. (1995): 53-63%

Gilbert and Clausen (2006): 72%Difficulties in Applying Permeable Pavements:

• Limited infiltration rate –useful in low intensity events but can fail to perform in intense storms.

• Already partially implemented – adequate modeling will require a street-by-street analysis.

• Intrusive and expensive to retrofit. – additionally will need regular maintenance

• Limited load – different load capacities result in different runoffs.

http://southcoastenergychallenge.org/blog/permeable-paving

http://www.google.es/imgres?um=1&hl=es&biw=1366&bih=589&tbm=isch&tbnid=Z2foqn80YSyQ1M:&imgrefurl=http://greenvalues.cnt.org/national/&docid=N0Cf9l598Q4GxM&imgurl=http://greenvalues.cnt.org/national/images/permeable_pavement.jpg&w=300&h=225&ei=6gWZUcmiL8Sk0AWCxoCoCA&zoom=1&ved=1t:3588,r:22,s:0,i:154&iact=rc&dur=511&page=2&tbnh=166&tbnw=228&start=17&ndsp=16&tx=103&ty=73

Specific SuDS –Ground Infiltration

Wide variety of options: rain gardens, soakaways, swales, ponds, etc.

Area intensive – Will be applicable in a significant manner for Tier C but not for Tier A.

Deemed unsuitable for London ground conditions. (Thames Water)

Roldin et al. (2012), Copenhagen-based study:

“The selected case study combines many of the worst possible conditions for infiltration”

Estimated a 10-30% annual runoff reduction through widespread soakaways and swales.(This being the ‘Realistic Scenario’)

http://www.buffalorising.com/2009/02/pushing-green-at-canal-side.html

http://greatecology.com/10-ways-low-impact-development-reduce-swurp-footprint-2/

Tier ATools with greatest potential:• Green roofs • Permeable pavements (but

suffer severe retrofit limitations)

Estimated global runoff effect:

Green Roofs – 23% annual runoff reduction respect to Tier’s total rainfall.Permeable pavements: impossible to estimate due to limited information. While Green roofs would provide important benefits, in terms of runoff reduction even ‘optimal’ retrofitting wont have a significant enough impact.

Source: Google maps

Tier CTools with greatest potential:• Green roofs • Permeable pavements (but

suffer severe retrofit limitations)

• Soakaways and Swales.

Estimated global runoff effect:

Green Roofs – 20% annual runoff reduction respect to Tier’s total rainfall.Soakways/Swales – 1m3 of storage per 13m2 of impermeable surface, results in 13,4% reduction of the annual runoff. SuDS runoff storage/attenuation would bring relief to traditional CSO systems, which would still be needed.

Minor disconnection scenarios might be possible.

Source: Google maps

Tier B

25 to Per. -25 50 to P. -500

10

20

30

40

50

60

70

80

90

Case Study in Putney Bridge, London

(Stovin et al. 2012)

Stovin et al._December Typical

Stovin et al._ October Typical

Stovin et al._ Annual typical

Scenarios

Runo

ff R

educ

tion

(%)

• 63% annual runoff reduction

• ~50% of impermeable surface disconnection.

• Ideal scenario, very difficult to implement in this Tier.

• Very vulnerable to intensive storms.

CSO drainage will be needed. However there is a large potential for SuDS-based attenuation which should be explored during CSO design.

Source: Google maps

Tier D

25 to Per. -25 50 to P. -500

20

40

60

80

100

120

Case Study in Frogmore(Stovin et al. 2012)

Stovin et al._December Typical

Stovin et al._ October Typ-ical

Stovin et al._ Annual typical

Scenario

Runo

ff R

educ

tion

(%

)

Markurssen at al. & Villareal et al. data coincides with Ashley et al.• 58% to 54% annual

runoff reduction • Easier to implement in

this Tier• Less vulnerable to

intense storms.

Suggests ample opportunity for integrating SuDS into CSO designs, reducing their designed intake.

Source: Google maps

Tier E

25 to Per. -25 50 to P. -5005

101520253035404550

Case Study in West Putney(Stovin et al. 2012)Stovin

et al._Decem-ber Typi-calStovin et al._ Octo-ber Typi-cal

Scenario

Runo

ff R

educ

tion

(%)

• 34% annual runoff reduction• However, Flow is

remarkably smaller to any other Tier

• Follows that vast open green area is already having a huge impact.

• Design might accommodate rainfall storage through ponds.

Existing -500

0.51

1.52

2.53

3.5

Flow ComparisonTier E_October 2000Tier E_AnnualTier D_October 2000Tier D_AnnualTier B_October 2000Tier B_Annual

Scenarios

Runo

ff F

low

(m

3/s)

SuDS should definitely be integrated into CSO Design, the large open areas should be explored as a way to integrate large disconnection scenarios.

ConclusionRunoff reduction:o Tier A: >23% o Tier C: >33

o Tier B: 63%o Tier D: 54-58%o Tier E: 34%

Ideal Global scenario:44.7% total annual

reduction

More detailed studies are needed in global SuDS scenarios as a whole, with emphasis on large population density areas (Tiers A and C)

http://www.google.com/imgres?um=1&sa=N&biw=1366&bih=665&hl=es&authuser=0&tbm=isch&tbnid=tyhcZg1klcVy7M:&imgrefurl=http://www.tourist-destinations.net/2013/01/london-travel-guide.html&docid=J6v3nxqsyMYDXM&imgurl=http://3.bp.blogspot.com/-i83l-2yiFRM/UOn56uDlQZI/AAAAAAAACBA/p4qK_ees5j8/s1600/london-.jpg&w=784&h=516&ei=RwGVUc-FBMaR7AburIGYBQ&zoom=1&ved=1t:3588,r:61,s:0,i:352&iact=rc&dur=955&page=4&tbnh=178&tbnw=260&start=54&ndsp=20&tx=100&ty=94

Thanks For Listening!

Please ask any Questions.

Cristobal Sapena LafuenteReg. Nº: 100164507

dissertation presentation_ suds inner london

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