Stormwater detention factors for a blue- green Leca®-roof based on lightweight expanded clay aggregate in Norway Jaran Raymond Wood R&D Manager Leca International
Hulevesi2020 23.9.2020 vesiyhdistys.fi/hulevesiseminaari #hulevesi2020 #vesiyhdistys Green roofs and Leca-materials
• Leca is expanded clay material • Made by heating natural clay in a rotary kiln • Strong, lightweight porous grains • Used as construction materials • Bulding blocks • Geotechnical • Agriculture • Water management • i.a. Documenting properties as detenion medium • Hypothesis RETENTION Run-off with and without Leca Precipitation Use of water Plant growth Transpiration
RegnintensitetRain intensity (mm) (mm)
AvrenningRun-off uten without fordrøyning Leca (L/s)
AvrenningRun-off med with fordrøyning Leca (L/s) (L/s) GREEN ROOF Overflow
Incoming Rain (mm) DETENTION runoff from other roofs Run-off Run-off intensity L/s)
Time (min)
Controlled flow Documenting properties as detenion medium
• Klima 2050 project in Norway • Climate adaptation program • Research council SFI • Consortium of 20 partners from industry, public, and academic organisations • www.klima2050.no Documenting properties as detenion medium
• Laboratory tests at SINTEF • Extreme event for 15 minutes’ rain interval at 27 mm/h, in 2% slope • Finely crushed Leca, 0-6 mm was ideal • Run-off measurements (FLL), calc. C-values Documenting properties as detenion medium
0 Event 45 80 24 • Full-scale pilot in Trondheim 0 72
• Fully instrumented 1 60 1 16 • Collecting data for 5 years 2 48
Field 1: Leca below permeable 3 36
paving blocks runoff [l/min] 2 8
rcptto [mm] precipitation 4 24 runoff [l/min] precipitation [mm] Field 2: Black, empty reference roof 5 12
Field 3: Leca under a traditional 3 6 0 0 green roof of sedum 20/4/ 20/4/ 21/4/ 21/4/ 21/4/ 21/4/ 21/4/ 22/4/ 22/4/ 22/4/ 22/4/ 22/4/ 22/4/ 23/4/ 23/4/ 23/4/ 23/4/ 23/4/ 23/4/ 24/4/ 24/4/ 24/4/ 24/4/ 26/7/ 26/7/ 26/7/ 26/7/
Klima 2050 Pilot Høvringen in Trondheim – green- and blue-grey roof (Photo: Tore Kvande, NTNU) Documenting properties as detenion medium
Leca test-field at Høvringen in Trondheim – green- and blue-grey roof (Photo: Tore Kvande, NTNU)
• Synthetic ”weather” • Extreme tests • Ongoing modelling PhD at NTNU Putting lab- and pilot-tests into practice Putting lab- and pilot-tests into practice
• Central place in Oslo city centre called ”Valkyrien” Putting lab- and pilot-tests into practice Requirements for building • Control of runoff, max 2 l/s • No digging of basins, tanks and pipes • Simulating nature acc. to climate strategy • Create a nice recreational area • Increase property value
Conclusions
• Extreme event for 15 minutes’ rain interval at 27 mm/h, in a 2% slope, was simulated on lightweight expanded clay aggregate (LECA) as a detaining subsurface for roofs. • The water detention was measured • Peak intensity reduction was observed.
• The permeability character of Leca give steady, but restricted flow of water through the media.
• The runoff coefficients (C) for the Leca-medium was calculated, and the behaviour for detention medium for larger areas was modelled.
• A blue-grey and green roof at a building in Oslo was installed with the suggested build-up.
• The project is a platform for experience sharing and will challenge construction customs when planning for local water management measures.
• The project will illustrate benefits of blue-grey and green roofs. And most importantly
• Blue-grey and green roofs can be combined as recreational areas and stormwater water management measurement • Blue-grey and greens roof can be an integral part to stop urban densification • Good planning and many fields of professional competence are certainly necessary to build a blue-grey and green roof Thank you for your attention
Acknowledgments: Thank you for your attention