THE ROLE OF GREEN ROOFS IN URBAN DRAINAGE A REVIEW OF THE CASE FROM AUGUSTENBORG ECO-CITY

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1 THE ROLE OF GREEN ROOFS IN URBAN DRAINAGE A REVIEW OF THE CASE FROM AUGUSTENBORG ECO-CITY Justyna Czemiel Berndtsson, PhD The work done at Water Resources Eng., Lund University, Sweden Currently Sydvatten Ltd company, Sweden

2 CONTENTS Background of the Augustenborg eco-city project (Sweden) Augustenborg s open storm water system Green roofs of Augustenborg: Influence on storm water quantity Influence on storm water quality (concentrations, loads, runoff quality changes with roof age) Major results are briefly presented for other studies of green roofs influence on runoff quality other extensive green roofs (Sweden) loads intensive green roof (Japan) first flush effect during simulated rain events Conclusions

3 AUGUSTENBORG ECO-CITY - BACKGROUND An example of integrated approach to revitalizing a degraded district in a city Build in 195s nice and modern, in 8s and 9s degraded and unattractive crime, unsafe, people moving out The municipal housing company and Malmö municipality need to act; lobby for support; succeed to get a grant from the Swedish Government 1998 (and later from EU) for turning Augustenborg into an attractive eco-city district

4 SUBPROJECTS OF THE AUGUSTENBORG ECO-CITY PROJECT Social aspects- work with the community (2% of residents participated), listening to the needs, consulting proposed solutions, reaching acceptance Investments in infrastructure buildings renovated Investments in the school, playgrounds for children and football field constructed, the house for elderly constructed; senior citizens activities launched Sewers rebuilt open storm water system constructed, no more flooding; green roofs introduced; green areas and biodiversity increased Source separation system for garbage designed according to tenants ideas Solar thermal power plant contributes to energy supply Malmö s first carpool Developed own job training programs Local community involved all throughout the process including formal design, information sessions, festivals

5 OPEN STORM WATER SYSTEM Elements: -Open channels -Ponds -Green infiltration surfaces -Permeable paving -Green roofs

6 CHANNELS

7 PONDS

8 GREEN INFILTRATION SURFACES GREEN (DRY) PONDS

9 PERMEABLE PAVING TO INCREASE INFILTRATION

10 GREEN ROOFS TO REDUCE RUNOFF

11 COMPARISON OF OUTFLOWS FROM DIFFERENT SYSTEMS M3/S (EXAMPLE FROM AUGUSTENBORG, MALMÖ, SWEDEN) System Rain, return period 5 years Conventional Rain, return period 1 years Open, dry initial conditions Open, wet initial conditions Villarreal et al., Ecol. Eng. 22, 24

12 ADVANTAGES OF OPEN STORM WATER SYSTEM Reduction of peaks Reduction of runoff volume Slow transport (lowers risk for urban sewer flooding, infiltration increases) Treatment of water Storage for use Recreation Biodiversity

13 GREEN ROOFS FROM AUGUSTENBORG, SWEDEN Influence on water quantity and quality

14 GREEN ROOFS Different roof sections have different vegetation (grasses, sedum, mosses and herbs), different soil thickness, type of drainage layer and different slopes. The green roof studied is a sedum-moss roof; 3 cm soil substrate; 1 cm crushed stone drainage layer; and a membrane protecting the original roof. The one roof section is 4 m long and 1.25 m wide sloping 2.6%. The soil substrate consists of 5% clay, 5% crushed limestone, 43% crushed roof tiles, 37% sand and 1% organic material.

15 GREEN ROOFS INFLUENCE ON STORM WATER QUANTITY WATER BALANCE Month (21- Precipitation mm Runoff mm Runoff reduction % 22) August September October November 5 29 December January February March April 28 5 May June 64 8 July month Bengtsson et al. (25) Nordic Hydrology 36(3)

16 DAILY RAINFALL (BLUE) RUNOFF (BLACK) The highest daily rainfall observed (22) was 28 mm and the corresponding highest runoff was 27 mm. If it rained during several consecutive days the runoff was close to the precipitation. Bengtsson et al. (25) Nordic Hydrology 36(3)

17 mm/min mm/min PEAK FLOWS FROM A THIN SEDUM-MOSS ROOF- RUNOFF PEAK REDUCED AND DELAYED,8,2,6,15 rai 3 min,4,1,2,5 runoff min , hour Rain (staples) and runoff (solid line) 7 August 21, and simulated runoff (dashed line) as mean rain intensity over 25 minutes. Rain intensity (thin line) and runoff(thick line) 17 October 22, and simulted runoff (dotted line) as mean rain intensity over 3 minutes. Bengtsson (25) Nordic Hydrology 36 (3)

18 GREEN ROOFS INFLUENCE ON RUNOFF WATER QUALITY

19 WATER QUALITY STUDIES Runoff water quality from the green roof as well as rain water quality have been studied during precipitation events: autumn 23, spring 25, autumn 26, spring 27, autumn 21* Bulk runoff samples and bulk rainwater samples were collected and analyzed for Tot-N, NO3-N, Tot-P, PO4-P, K, DOC and heavy metals (Cd, Cu, Pb, Ni, Zn) During 21 sampling by Naeem Ahmed, master thesis

20 NO₃-N (mg/l) Tot-N (mg/l) PO₄-P (mg/l) Tot-P (mg/l) CONCENTRATIONS IN GREEN ROOF RUNOFF AND RAIN WATER CHANGES WITH ROOF AGE,3,25,2,15,1,5 rain water green roof,35,3,25,2,15,1,5 rain water green roof 1,4 1,2 1,8,6,4,2 rain water green roof 4 3,5 3 2,5 2 1,5 1,5 rain water green roof

21 Cd (mg/l) Cu (mg/l) K (mg/l) DOC (mg/l) CONCENTRATIONS IN GREEN ROOF RUNOFF AND RAIN WATER CHANGES WITH ROOF AGE Autumn 3 Spring 5 Autum 6 Spring 7 Autumn 1 rain water green roof rain water green roof,25,1,2,8,15,6,1,5 rain water Green roof,4,2 rain water Green roof

22 Zn (mg/l) Ni (mg/l) Pb (mg/l) CONCENTRATIONS IN GREEN ROOF RUNOFF AND RAIN WATER CHANGES WITH ROOF AGE,25,2,15,1,5 rain water Green roof,35,3,25,2,15,1,5 rain water Green roof Autumn6 Spring7 Autumn1,1,8,6,4,2 rain water Green roof

23 INFLUENCE OF VEGETATED ROOFS ON RUNOFF WATER QUALITY Comparison between concentrations in rain water and the green roof runoff in general for all studied seasons Increase Decrease Varying PO4-P (substantially) Tot-P (substantially) K (substantially) DOC (substantially) Cu (substantially) Ni (somewhat) NO3-N (substantially) Tot-N (somewhat) Cd (somewhat) Pb (somewhat) Zn

24 ESTIMATED ANNUAL WET DEPOSITION AND ANNUAL* LOAD FROM THE STUDIED VEGETATED ROOF AT AUGUSTENBORG Annual load Tot-N Tot-P K Cr Cu Fe Mn Pb Zn In precipitation [mg/m 2 year] ,18 1,44 12,8 1,44 2,16 7,76 In green roof runoff [mg/m 2 year] ,7 5,72 15,4 1,1,15 7,11 *average from results obtained during one year of 23 notice that different metals were studied

25 MAJOR RESULTS ARE BRIEFLY PRESENTED FOR OTHER STUDIES OF GREEN ROOFS INFLUENCE ON RUNOFF QUALITY -other extensive -intensive -first flush during simulated events

26 STUDY OF EXTENSIVE GREEN ROOFS,SWEDEN LOADS ARE COMPARED (ONE YEAR)

27 RM-RAIN MALMÖ; CV-CANOE HOUSE GREEN; AV-AUGUSTENBORG GREEN; AT-AUGUSTENBORG TILE; RL-RAIN LUND; KV-BICYCLE SHELTER GREEN; GV- GUNNESBO GREEN; GC-GUNNESBO CONCRETE. IN MG/M 2 AND YEAR NO 3 - N 5 AT PO 4 - P RM GC RL KV GV CV AV K KV AV CV RM AT RL GV GC 35, 3, 25, AV GC 2, 15, CV KV GV 1, 5,, RM AT RL

28 RM-RAIN MALMÖ; CV-CANOE HOUSE GREEN; AV-AUGUSTENBORG GREEN; AT-AUGUSTENBORG TILE; RL-RAIN LUND; KV-BICYCLE SHELTER GREEN; GV- GUNNESBO GREEN; GC-GUNNESBO CONCRETE. IN MG/M 2 AND YEAR 3, 25, 2, 15, 1, 5,, RM CV Cu AV AT RL KV GV GC 7, 6, 5, 4, 3, 2, 1,, RM CV AV Fe AT RL KV GV GC Pb Zn 2,5 2, 1,5 1, RM CV AT GV 16, 14, 12, 1, 8, 6, AT GC,5, AV RL KV GC 4, 2,, RM CV AV RL KV GV

29 INTENSIVE GREEN ROOF FUKUOKA ACROS, JAPAN

30 VEGETATION: 35 PLANTS, 76 SPECIES

31 K (mg/l) DOC (mg/l) Tot-N (mg/l) NO3-N (mg/) RUNOFF QUALITY FROM GREEN ROOFS INTENSIVE JAPAN (J) EXTENSIVE SWEDEN (S) Rain S Roof S Rain J Roof J1 Roof J2. Rain S Roof S Rain J Roof J1 Roof J Rain S Roof S Rain J Roof J1 Roof J2 1 Rain S Roof S Rain J Roof J1 Roof J2

32 Pb (mg/l) Zn (mg/l) PO4-P (mg/l) Tot-P (mg/l) RUNOFF QUALITY FROM GREEN ROOFS INTENSIVE JAPAN (J) EXTENSIVE SWEDEN (S) Rain S Roof S Rain J Roof J1 Roof J2. Rain S Roof S Rain J Roof J1 Roof J Rain S Roof S Rain J Roof J1 Roof J2. Rain S Roof S Rain J Roof J1 Roof J2

33 Tot-P (mg/l) NO3-N (mg/l) Tot-P (mg/l) Fe (mg/l) FIRST FLUSH DURING SIMULATED RAIN EVENTS SD-SWEDEN DRAINAGE, S-SWEDEN, NO DRAINAGE; J JAPAN, M MAINS SUPPLY WATER SD S.25.2 SD S SD SD S SD SD S S S M M M M M Simulated rain (mm) S M SD M M M S M SD S SD SD S Simulated rain (mm) J J J J M M M M Simulated rain (mm) J M M M M J J J Simulated rain (mm)

34 c-co (mg/l) Cu (SD) FIRST FLUSH (1) For nearly all studied runoff constituents (roofs SD, S, and J) in first runoff sample higher concentrations; Concentration changes expressed as a first order law as a function of runoff depth x indicate first flush; dc/dx=-kx, therefore c-c =c 1 e -(kx), where c-concentration at runoff depth x, c -leveling-off concentration, c 1 -initial concentration of decrease, k-wash-off coefficient FF for: SD: T-P, Cu, Zn S: T-P, NH4-N, Zn J: T-P, NO3-N.2.1 y =.178e x R 2 = x (mm)

35 Normalized cumulative Fe mass (SD) Normalized cumulative Tot-P mass (S) FIRST FLUSH (2) Tested if on the plots of normalized cumulative mass as a function of normalized cumulative flow the values are above the diagonal line which would indicate first flush (more mass washed off in earlier runoff (Kim et al, 25). First flush for all studied components and roofs except for K and DOC Normalized cumulative flow Normalized cumulative flow

36 CONCLUSION WATER QUANTITY Runoff from green roof is reduced compared to precipitation on annual and monthly basis During days with consequent precipitation events runoff is almost equal precipitation The runoff peaks from green roofs are lower and delayed comparing with precipitation peaks. This influences the time of concentration in urban catchment and lowers risk for flooding

37 CONCLUSION WATER QUALITY Regarding runoff water quality and comparing it with rain water quality it is observed that PO4-P, Tot-P, K, and DOC; Cu, Ni concentrations in green roof runoff increase NO3-N, Tot-N, Cd, Pb concentrations decrease in runoff The release of PO4-P, Tot-P, K, Cu from green roof decrease with roof age

38 CONCLUSION OTHER ROOFS The concentrations of following substances were found larger in runoff from extensive than intensive studied roofs: DOC, Tot-N, Tot-P, PO4- P, Zn. Release of K was found larger from intensive than extensive roof. First flush is observed during simulated rain events from both intensive and extensive roofs with regard to all measured substances except K and DOC.

39 Thank you