Water sensitive urban design

Transcription

1 WSUD in your backyard Living Smart Mellissa Bradley, Program Manager 16 May 2017 Water sensitive urban design. is an approach to urban planning and design that integrates the management of the total water cycle into the land use and development process 1

2 Principles Re-integrate water back into urban landscape create microclimate Re-use of water at source (or close as possible) Protect receiving water quality (streams and marine) Fit for purpose water use Water sensitive communities Liveable Sustainable Source: P.Coombes Productive Resilient 2

3 Urbanisation and changes to catchment hydrology Water on a hectare of forest over a year Source: Centre for Water Sensitive Cities 3

4 Water on a hectare of forest over a year Source: Centre for Water Sensitive Cities Replace the forest with a building Source: Centre for Water Sensitive Cities 4

5 Source: Centre for Water Sensitive Cities Change to hydrograph 5

6 Reducing stormwater runoff benefits water cycle Source: Coutts et al. (2012) Allotment WSUD Solutions Collection and reuse of rainwater and stormwater on site onsite detention onsite retention rain gardens vegetated swales and buffer strips direction of flow from impervious ground surfaces to landscaped areas. Reduced impervious areas site coverage permeable paving Water conservation 6

7 Onsite retention and re-use of stormwater Factors in tank size selection Supply v demand Yields will be dependant on: annual rainfall roof area connected to tank Amount of and frequency of rainwater use: indoor (toilet, laundry, hot water service Outdoor (garden, leaky tank ) Capacity of the tank connected to roof 7

8 Communications Technical Resources Communications 8

9 Roof area to be connected to rainwater tank (m²) Percentage of time rainwater tank will meet full domestic internal daily demand KENT TOWN (Average Annual Rainfall 583 mm) Rainwater Use Option Description Tank Capacity (L) High internal use 11L single flush toilet, 100% laundry (front load WM) & HWS Medium internal use 1 (6/3L) Dual flush toilet, AAA-rated shower head, 100% laundry (top load WM) & HWS Medium internal use 2 (6/3L) Dual flush toilet, AAA-rated shower head, 100% laundry (front load WM) & HWS Low grade uses (6/3L) Dual flush toilet and 100% laundry (front load WM) only 1,000 2,000 5,000 1,000 2,000 5,000 1,000 2,000 5,000 1,000 2,000 5,000 9, % 11% 11% 17% 19% 19% 23% 27% 28% 51% 59% 65% 68% % 26% 30% 30% 40% 47% 39% 50% 60% 65% 77% 87% 97% % 36% 46% 37% 50% 63% 47% 60% 72% 71% 83% 95% 100% % 42% 56% 41% 55% 70% 51% 65% 79% 74% 87% 98% 100% Assumptions: The internal water use estimates are based upon a 3 person household. Supersize your rainwater tank Size (L) Material Min Max 1,000 L poly $385 $425 2,000 L poly $485 $1,750 5,000 L poly $730 $1,450 10,000L poly $1,280 $1,900 2,000L underdeck Size (L) Material Typical 1,000 L Galv. steel $860 2,000 L Galv. steel $1,025 5,000 L Galv. steel $1,450 10,000L Galv. steel $1,850 Note: Prices are indicative only 3,000L modular 2,000L slimline 9

10 Rainwater tank collection system Source: 1. Roof surface condition 2. Gutter mesh (6mm wire mesh) 3. Gutter outlets 4. Rain heads. 5. First flush water diverters. 6. Tank screen 7. Water tank size. 8. Insect proof screens or flap valves for tank overflow outlets. 9. Tank (mains) top up 10. Pump system 11. Filter Typical cost: Plumbing (labour) $450-$800 Pump system $500-$800 Filter $400-1,000 Maintenance of water quality Clean gutters and screens Vacuum sediments from bottom of tank Replace filter cartridges 10

11 Reduced impervious areas The 100m2 house Dwelling footprint A 100m2 Allotment Size = 400m2 Site coverage = 25% Source: Levesque & Derrick Architects, lada.com.au 11

12 5,000L rainwater tank for: Toilet flushing Laundry garden Source: Levesque & Derrick Architects, lada.com.au Source: Levesque & Derrick Architects, lada.com.au 12

13 Source: Levesque & Derrick Architects, lada.com.au Minimise impervious surface areas by: Source: Source: Source: Source: 13

14 Permeable pavements Source: Source: Modi Building Technology Source: Baden Myers Vegetated Swales and buffer strips 14

15 Swales Source: Remove sediments Promote infiltration Delay runoff peak flow Source: Melbourne Water Swale Unless the swale is discharging to an existing stormwater surface pit, an inground raingarden or infiltration raingarden, it will need to be fitted with an overflow pipe connected back into the stormwater system. Source: Melbourne Water 15

16 Material List 2 m 2 Swale Approx. cost $200 - $300 (plus the cost of a plumber). Source: Melbourne Water Maintenance Once established don t need to be watered or fertilised. Some weeding needed until plants have matured. Evenly distribute water flow into the swale to limit erosion from heavy rainfall - strategically placed rocks may help with - flow spreader can be attached to the end of the downpipe. 16

17 Raingardens Raingardens Manage excess rainfall Reintegrate water in urban environment (if unlined) Remove pollutants from rainwater or stormwater 17

18 Raingardens - Overview Source: Designflow 18

19 How to construct a raingarden Tips 1. Soil mix needs some clay (up to 3%) and organic matter (up to 5%) to retain moisture between rainfall events 2. If your raingarden is greater than 4m wide install two slotted drainage pipes (evenly spaced) and two overflow pipes Communications 19

20 Raingarden Species Selection Planting zones Figure 1 Raingarden zones for plant selection Plant species proven to be effective at Nitrogen removal Adapted from EPA Raingarden 500 guidelines 20

21 Plant species proven to be effective at Nitrogen removal Adapted from EPA Raingarden 500 guidelines Plant species for companion planting Adapted from EPA Raingarden 500 guidelines 21

22 How to size your raingarden Area of run-off (m²) Area of raingarden (approx.) (m²) Mellissa Bradley Program Manager mellissa@watersensitivesa.com