Hydrology/Stormwater. Tom Ballestero University of New Hampshire Stormwater Center. Urban Forestry Workshop February 2013

Transcription

1 Hydrology/Stormwater Tom Ballestero University of New Hampshire Stormwater Center Urban Forestry Workshop February 2013 Biophysical Services of the urban forest 1

2 Low Impact Development and Green Infrastructure Stormwater management that starts with site layout and design plus includes systems designed to create hydrologic transparency 2

3 Types of Processes Hydraulic control Storage Sedimentation Filtration Infiltration Sorption Biodegradation (microbial, rhizospheric, plant) Chemical 3

4 Filtration constructed systems Porous Asphalt Pervious Concrete Permeable Pavers Sand Filter Ecoroof 4

5 Filtration i Biological i l Gravel Wetland Tree Filter Bioretention System (rain garden) 5

6 Bioretention 6

7 Parking Lot Bioretention 7

8 Retrofit Bioretention 8

9 Retrofits connect to existing infrastructure t 9

10 Parking Lot Retrofit 10

11 Tree Box Filter 11

12 UNH Tree Filter 12

13 Tree Filter Boston, MA 13

14 Retrofit Tree Filter 14

15 Vegetation Native plants always the best Cooperative Extension, USDA, NRCS good sources Forest Meadow Transition Ornamental 15

16 Subsurface Gravel Wetland 16

17 Nitrification NH 4 N0 2 NO 3 Aerobic Zone Forebay and surface of wetland Influent Organic N from runoff and plant debris Denitrification N 2 (gas) Anaerobic Zone Subsurface gravel

18 UNH Subsurface Gravel Wetland 18

19 Dissolved Oxygen in Gravel Wetland Effluent Flow Dissolved Oxygen

20 100% of N mass in first 0.1 in runoff or 10% of WQV Q 90% of N mass in first 0.2 in runoff or 20% of WQV V ISR /WQV =0.2 V ISR /WQV =0.1 ISR Q ISR Mass loading for DRO, Zn, NO3, TSS as a function of normalized storm volume for two storms: s: (a) a large age 2.3 in rainfall a oe over 1685 minutes; (b) a smaller 0.6 in storm depth over 490 minute. DRO=diesel range organics, Zn= zinc, NO3= nitrate, TSS= total suspended solids

21 Hydraulic Performance 21

22 Flow and Volume Attenuation Average Annual Peak Flow Reduction is 68% Average Annual Lag Time is 790 min 22

23 Hydraulic Efficiency k p P E 1 PI k L T E T I 1 23

24 Hydraulic Performance Lag Time (k L ) Peak Reduction (k P )

25 Tree Filter Volume Reduction Long term water volume reduction = 33% Specific storm Volume reduction = f(precipitation depth, AMC) Date Storm depth Volume Peak Flow (in) reduction (%) Reduction (%) April May *9 July *precipitation previous two days 25

26 Soil Limitation? 26

27 Conventional LID Site: Site: Conventional design connected impervious surfaces Lawn Rooftop disconnected imperviousness Rooftop to bioretention 1 WQV, overflow to PA driveway Driveway and Roadways as PA Lawns to PA 65% UDC, <10% EIC (NHDES requirements) CB Conventional design LID design Pavement 27

28 LID design 65%UDC Rooftop Lawn Porous Pavement Bioretention 28

29 Total runoff Volumes Total Runoff Volumes for Each Scenario per 1 Acre of Development in Type A soil Total Runoff Volumes for Each Scenario per 1 Acre of Development in Type C Soil umes (cf) LID-volume (cf) Predevelopment-volume (cf) Conventional-volume (cf) lumes (cf) 30,000 25,000 20,000 LID-volume (cf) Predevelopment-volume (cf) Conventional-volume (cf) tal Runoff Vol To To otal Runoff Vol 15,000 10,000 5, yr 10yr 100yr 2yr adj 10yr adj 100yr adj 1 2yr 10yr 100yr 2yr adj 10yr adj 100yr adj Design storm Design storm 29

30 Water Quality Performance 30

31 TSS Removal Efficiencies emoval Eff ficiency TSS % R

32 TP Removal Efficiencies iciency TP % Re emoval Eff

33 DIN Removal Efficiencies DIN % Removal Efficiency 10 0

34 TSS Removal Performance

35 Nitrogen Removal Performance

36 Phosphorous Removal Performance

37 2009 Summer Temperatures 7 days Porous Asphalt Subsurface Gravel Wetland Retention Pond Grass Swale 37

38 Cold Weather 38

39 Frost Penetration 39

40 Filter Media Frost Penetration epth (cm ) Frost D 1/13/2005 1/28/2005 2/10/2005 2/25/2005 3/10/2005 3/25/ (C) Avg Daily Temp B-Sand D-Bio G-Gravel Rain Ave. Temp 40

41 Retrofit Strategies 41

42 School Street School Retrofit, Rochester NH Porous asphalt Bioretention Infiltration ti basin Tree Filter Pervious concrete

43 Distribution of IC Type Will enable targeting of IC reduction 43

44 Land use for WB Watershed 44

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46 Realities ID Low hanging fruit Substantial reductions in pollutant loading could be achieved by addressing some of the areas with relatively low land cover but high loading and imperviousness Commercial and industrial 46

47 Cost Technology Cost ($/A imp.) Grassed swale 11,200 Rip rap swale 11,951 Sand Filter 12,417 Retention Pond 13,662 VortSentry (VS40) 18,000 CDS PMSU ,000 Environment t21 V2B1 21, Gravel Wetland 22,327 Tree Filter 22,651 Bioretention 25,104 AquaSirl and AquaFilter 40,044 ADS Water Quality unit & infiltration 50,009 Porous asphalt 58,370

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51 Hidden/Unconsidered Costs Water quality degradation Lost recreational values Watershed hdimpairments i (death by 1,000 cuts) Property values Uncontrolled contaminants (temperature, energy) Sustainability (water supply, low flow) 51

52 What Does This Mean? You and I subsidize any development that only employs curb, gutter, swales, ponds..and the site developer profits from the costs we bear as taxpayers or as stakeholders in environmental quality 52

53 Ecosystem Services Hydrologic Water quality Plants Birds Insects Amphibians Pet waste management Connectivity 53

54 Human Dimensions Visual/Scenic Urban green space Shade 54

55 Barriers The Impossible Challenges Maintenance Misperceptions Costs Ease of permitting traditional technologies Acceptance Designer/Regulator Unfamiliarity Turf management 55

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