Stormwater Asset Management Using Gis V5

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Stormwater Asset Management Using Gis V5

  1. 1. Stormwater Asset Management Using GIS Vithal V. Deshpande, Environmental Coordinator, City of Somerville, Massachusetts, and Britta Roden, M.S. Economics Candidate Tufts University May 4, 2005 Environmental Expo & Conference Seaport World Trade Center Boston, MA
  2. 2. Acknowledgement <ul><li>USEPA Region 1 for Funded this project under Water Quality Agreement Grant. </li></ul><ul><li>Tufts University provided GIS computing resources. </li></ul><ul><li>Denise Castronovo (Tufts Academic Technology Department) and Prof. Jeff Zabel (Economics Department) provided helpful comments. </li></ul>
  3. 3. About Somerville <ul><li>Located within the lower Mystic River basin and is surrounded by the Mystic River and Alewife Brook along its western and northern parts. </li></ul><ul><li>Somerville is the most densely populated urban area in Massachusetts, with a population density of 18,868.1 people per square mile, [4.1 square miles] (Census2000). </li></ul><ul><li>Given the relatively small space that is shared by the 77,478 Somerville residents, it is crucial to make pollution prevention a priority. </li></ul>Credit for photographs on this slide: Jonas A. Kahn, © 2004
  4. 4. Where is Somerville?
  5. 5. Stormwater Issues <ul><li>Environmental hazards in the Mystic River include: </li></ul><ul><ul><li>chemicals leaching from waste disposal sites, </li></ul></ul><ul><ul><li>contaminated sediments, excessive inputs of plant nutrients, </li></ul></ul><ul><ul><li>discharges of sewage containing pathogenic bacteria, and </li></ul></ul><ul><ul><li>inputs of fuel hydrocarbons, road salt and toxic metals in stormwater runoff. </li></ul></ul>
  6. 6. Approach <ul><li>Environmental Management System at its core but without formal adoption. </li></ul><ul><li>Information Technology implementation for interactive database. </li></ul><ul><li>Geographic Information System (GIS) utilization to mapping BMPs </li></ul><ul><li>Analysis of “Green Cover” from Stormwater and Environmental Perspective </li></ul><ul><li>Integration with Stormwater Management </li></ul>
  7. 7. Environmental Management System <ul><li>Continuous Improvement Process </li></ul>Inventory Impact Improvement
  8. 8. Stormwater Pollution Reduction Initiatives <ul><li>Elimination of combined sewer overflows (CSOs) and dry weather overflows </li></ul><ul><ul><li>9 out of 11 CSOs are eliminated </li></ul></ul><ul><li>Monitoring water quality </li></ul><ul><ul><li>EMPACT Project – 2 years of real time monitoring </li></ul></ul><ul><ul><ul><li>www.mysticriveronline.org or www.epa.gov/empact </li></ul></ul></ul><ul><li>Stormtreat Installation at Alewife Brook </li></ul><ul><li>Pollution Prevention </li></ul><ul><li>Hazardous Waste Collection </li></ul><ul><li>Street Sweeping </li></ul><ul><li>Public Awareness Campaign </li></ul><ul><li>Trees </li></ul><ul><li>Catch basin Cleanup </li></ul>
  9. 9. Inventory Analysis <ul><li>Best Management Practices </li></ul><ul><ul><li>Structural </li></ul></ul><ul><ul><li>Non-Structural </li></ul></ul><ul><li>Departments </li></ul><ul><li>BMP Status </li></ul><ul><ul><li>Ongoing (Functioning) </li></ul></ul><ul><ul><li>Under Consideration </li></ul></ul><ul><li>Cost </li></ul><ul><ul><li>Personnel </li></ul></ul><ul><ul><li>O&M </li></ul></ul><ul><ul><li>Budget </li></ul></ul>
  10. 10. Database Development <ul><li>Microsoft Access Database </li></ul><ul><li>Customized for Somerville Operation </li></ul>
  11. 11. Stormwater Asset Management System <ul><li>Customized Forms </li></ul><ul><li>Customized Reports </li></ul><ul><li>Easy for Management Review </li></ul>
  12. 12. Geo Information System (GIS) <ul><li>GIS overlays for structural BMPs </li></ul><ul><li>Includes location and cost of BMPs. </li></ul><ul><li>BMPs included for GIS Overlays </li></ul><ul><ul><li>Catch Basin Maintenance </li></ul></ul><ul><ul><li>Combined Sewer Overflows (CSOs) </li></ul></ul><ul><ul><li>Stormdrains Street Sweeping </li></ul></ul><ul><ul><li>Stormtreat System </li></ul></ul>
  13. 13. GIS – Storm Drains
  14. 14. GIS - Catch Basins
  15. 15. GIS – Combined Sewer Overflows (CSOs)
  16. 16. GIS - Stormtreat
  17. 17. GIS – Street Cleaning
  18. 18. Water Quality Mystic River & Alewife Brook <ul><li>Lower Mystic River and Alewife Brook are surrounded by Somerville, Cambridge, Medford and Arlington </li></ul><ul><li>Loss of recreational opportunities due to CSOs and wet weather discharges. </li></ul><ul><li>Several test data available from governmental agencies, research institutions and non-profits. </li></ul><ul><li>No uniformity in data was observed, hence no data was considered for inventory at this time. </li></ul>Collecting and evaluating water quality data near BMPs will be considered in the next stage of the project
  19. 19. Tree Cover as BMP <ul><li>Pervious versus Impervious Surfaces </li></ul><ul><li>Pervious: rainwater is filtered, recharges into groundwater </li></ul><ul><li>Impervious: surface runoff, pollutants wash into rivers </li></ul><ul><li>Why Trees? </li></ul><ul><li>intercept the rainwater </li></ul><ul><li>slow down flow and movement towards the drainage area </li></ul><ul><li>reduce volume of stormwater and peak flow rates </li></ul><ul><li>less surface runoff, less pollutants wash into rivers </li></ul><ul><li>AmericanForests tree canopy targets: </li></ul><ul><li>25% for urban residential zones </li></ul><ul><li>15% for central business districts </li></ul>
  20. 20. Impact of Trees on Stormwater Runoff Runoff Volume Time less trees more trees HYDROGRAPH
  21. 21. CITYGreen <ul><li>Software Developed by American Forests ( www.americanforest.org ) </li></ul><ul><li>Estimates stormwater runoff, time of concentration, and peak flow during a rainstorm </li></ul><ul><li>Results: </li></ul><ul><li>1) volume of water that trees prevent from turning into runoff </li></ul><ul><li>2) Economic value of tree cover </li></ul><ul><li>3) Air Quality benefits of tree cover </li></ul>
  22. 22. <ul><li>Runoff volume is computed from: </li></ul><ul><li>tree canopy coverage </li></ul><ul><li>average rainfall </li></ul><ul><li>soil type </li></ul><ul><li>slope </li></ul><ul><li>other land cover features </li></ul>CITYGreen – Inputs Computations based on TR-55 algorithm developed by the Natural Resource and Conservation Service at the Department of Agriculture
  23. 23. <ul><li>Satellite imagery from Digital Globe (June 2004) with leaves </li></ul><ul><li>Image classification using Erdas Imagine software </li></ul><ul><li>CITYGreen uses classified satellite image to create a land cover file </li></ul><ul><li>CITYGreen analysis: Somerville digital elevations model for slope, classified land cover image, and Boston rainfall average and soil composition </li></ul><ul><li>Analysis for Somerville and individual neighborhoods </li></ul>CITYGreen Methodology
  24. 24. Satellite Imagery
  25. 25. CITYGreen Landcover Classification
  26. 26. Tufts University Area False Color Image, red represents trees, grass, lawn
  27. 27. Tufts University Area Landcover Classification
  28. 28. Somerville Neighborhoods
  29. 29. CITYGreen Calculations - I <ul><li>Curve Numbers: </li></ul><ul><li>CN (weighted) = Total Product of (CN x Percent land cover area) / Total Percent Area or 100 </li></ul><ul><li>Potential Maximum Retention after Runoff begins: </li></ul><ul><li>S = ( (1000 / CN) - 10) </li></ul><ul><li>Runoff Equation: </li></ul><ul><li>Q = [ P - 0.2 ((1000 / CN) - 10) ]2 / P + 0.8 ((1000 / CN) - 10) </li></ul><ul><li>Flow Length: </li></ul><ul><li>F = (total study area acres0.6) * 209.0 </li></ul><ul><li>Lag Time: </li></ul><ul><li>L = ((F0.8) *((S + 1.0) 0.7) / (1900 * ((slope)0.5))) </li></ul><ul><li>Time of Concentration: </li></ul><ul><li>Tc = 1.67 * L </li></ul><ul><li>Unit Peak Discharge: </li></ul><ul><li>log(qu) = C0 + C1log(Tc) + C2[log(Tc)]2 </li></ul><ul><li>Peak Flow: </li></ul><ul><li>Peak = (qu * Am * Q * Fp) </li></ul><ul><li>Storage Volume: </li></ul><ul><li>Vs = Vr *(C0 + (C1(qo/qi)) + (C2 ((qo/qi) (qo/qi))) + (C3 (qo/qi) * (qo/qi) * </li></ul><ul><li>(qo/qi))) * study area acres * 43560.17 / 12 </li></ul>
  30. 30. CITYGreen Calculations - II <ul><li>Variable Definitions </li></ul><ul><li>P = Average Rainfall for a 24 hour period (inches) </li></ul><ul><li>Am = study area acres / 640 to determine square miles </li></ul><ul><li>Fp = Swamp pond percentage adjustment factor </li></ul><ul><li>qo =Existing peak flow condition with trees </li></ul><ul><li>qi = Peak flow without trees </li></ul><ul><li>C0..... = TR-55 Coefficients in accordance with rain type </li></ul><ul><li>Output Values </li></ul><ul><li>Peak = Peak Flow (cfs) </li></ul><ul><li>Vs = Storage volume (cubic feet) </li></ul><ul><li>Vr = Runoff Volume (in) </li></ul><ul><li>CN = Runoff Curve Number (weighted) </li></ul><ul><li>Q = Runoff (inches) </li></ul><ul><li>F = Flow length (feet) </li></ul><ul><li>S = Potential Maximum Retention after Runoff begins (in) </li></ul><ul><li>L = Lag Time (hours) </li></ul><ul><li>Tc = Time of Concentration (hours) </li></ul><ul><li>qu = Unit Peak Discharge (csm / in) </li></ul>
  31. 31. City Green Report for Air Pollution and Carbon Sequestration T
  32. 32. City Green Report for Stormwater
  33. 33. City Green Analysis Neighborhoods Summary 2.8 % 18.0 % 6.6 % 72.7 14.3 % 22.5 % 35.9 % Somerville 0.2 % 18.8 % 7.3 % 73.8 15.4 % 22.1 % 36.3 % Winter Hill 0.3 % 25.3 % 8.2 % 66.4 15.4 % 20.3 % 30.7 % West Somerville 0 % 9.6 % 4.5 % 85.7 11.7 % 28.0 % 46.0 % Ward2/CobbleHill 0 % 30.5 % 9.2 % 55.0 17.0 % 18.2 % 25.1 % Tufts 3.5 % 19.7 % 7.5 % 69.3 13.5 % 21.6 % 34.2 % Ten Hills 0.1 % 23.7 % 8.2 % 68.0 16.5 % 20.4 % 31.1 % Spring Hill 0.1 % 21.9 % 7.5 % 70.4 15.5 % 21.3 % 33.6 % Prospect Hill 0 % 23.6 % 9.1 % 67.4 16.0 % 19.4 % 32.0 % Powderhouse 0.7 % 21.3 % 6.9 % 71.1 14.2 % 20.7 % 36.2 % Magoun / Albion 13.3 % 10.6 % 4.7 % 71.4 12.9 % 22.6 % 35.9 % East Somerville 0.1 % 22.1 % 7.5 % 70.3 17.3 % 20.1 % 32.9 % Davis Square 0.1 % 25.6 % 8.3 % 66.1 15.3 % 20.6 % 30.2 % Central Hill Water Area Trees Open Space: Grass Impervious Total Impervious Surfaces: Unpaved Impervious Surfaces: Paved Impervious Surfaces: Buildings Somerville Neighborhood
  34. 34. CITYGreen Neighborhoods Stormwater Analysis $8,630,078 4,315,039 4.09 3.68 -39.47 39.21 -19.56 Somerville $584,374 292,187 4.09 3.76 -30.83 27.93 -15.67 Winter Hill $735,965 367,983 4.26 3.76 -38.95 44.95 -21.88 West Somerville $1,581,130 790,565 3.84 3.61 -33.49 22.60 -13.24 Ward2/CobbleH $525,687 262,843 4.44 3.76 -44.78 62.57 -27.32 Tufts $734,613 367,307 4.09 3.68 -39.47 36.42 -19.56 Ten Hills $739,524 369,762 4.26 3.76 -38.95 44.60 -21.88 Spring Hill $377,437 188,718 4.17 3.76 -35.25 34.35 -18.89 Prospect Hill $388,322 194,161 4.26 3.76 -38.95 44.51 -21.88 Powderhouse $485,224 242,612 4.17 3.68 -43.34 44.27 -22.63 Magoun/Albion $1,305,089 652,545 3.84 3.61 -33.49 22.35 -13.24 East Somerville $615,832 307,916 4.17 3.76 -35.25 37.74 -18.89 Davis Square $190,339 95,170 4.26 3.76 -38.95 39.88 -21.88 Central Hill Total Stormwater Savings Storage volume needed cu.ft Runoff in inches w/out trees Runoff in inches w/ trees Infiltration % change Peak Flow % change Time of Concentration % change Somerville Neighborhood
  35. 35. CITYGreen – Neighborhoods Summary Chart
  36. 36. CITYGreen Neighborhoods Air Pollution Removal 124580 50689 4143 5521 28824 14052 32379 10539 58591 19071 643 1506 Somerville 8686 2338 289 385 2010 980 2257 735 4085 133 45 105 Winter Hill 12689 5163 422 562 2936 1431 3298 1074 5968 1943 65 153 West Som. 12400 5045 412 549 2869 1399 3223 1049 5832 1898 64 150 Ward2 CobbleH 9713 3952 323 430 2247 1096 2525 822 4568 1487 50 117 Tufts 11877 3627 395 526 2748 134 3087 1005 5586 1818 61 144 Ten Hills 11897 4840 396 527 2753 1342 3092 1006 5595 1821 61 144 Spring Hill 6003 2443 200 266 1389 677 1560 508 2823 919 31 73 Prospect Hill 6198 2522 206 275 1434 699 1611 524 2915 949 32 75 Powderhouse 6966 2834 232 309 1612 786 1810 589 3276 1066 36 84 Magoun, Albion 24998 10172 831 1108 5784 2820 6497 2115 11757 3827 129 302 East Somerville 9854 4009 328 437 2280 1111 2561 834 4634 1508 51 119 Davis Square 3305 1345 110 146 765 373 859 280 1554 506 17 40 Central Hill Value lbs/yr Value lbs/yr Value lbs/yr Value lbs/yr Value lbs/yr Value lbs/yr   Total SO 2 Particulate Matter NO 2 Ozone CO Somerville Neighborhood
  37. 37. CITYGreen Analysis Carbon Storage & Sequestration 18.0 % 488.1 188.61 24,227.09 Somerville 18.8 % 38.8 13.15 1,689.05 Winter Hill 25.3 % 56.8 19.21 2,467.84 West Somerville 9.6 % 54.7 18.77 2,411.33 Ward2/CobbleHill 30.5 % 43.9 14.71 1,888.98 Tufts 19.7 % 45.7 17.98 2,309.95 Ten Hills 23.7 % 53.5 18.01 2,313.62 Spring Hill 21.9 % 27.0 9.09 1,167.26 Prospect Hill 23.6 % 28.0 9.38 1,205.23 Powderhouse 21.3 % 30.5 10.55 1,354.55 Magoun / Albion 9.6 % 50.1 37.85 4,861.33 East Somerville 22.1 % 44.3 14.92 1,916.12 Davis Square 25.6 % 14.9 5.00 642.66 Central Hill Percent Tree Cover Tree Cover in acres Total Tons Sequestered (annually Total Tons Stored Somerville Neighborhood
  38. 38. Major Findings of CITYGreen Analysis <ul><li>Somerville has 18% tree cover on average </li></ul><ul><li>(9.6 – 30.5%) </li></ul><ul><li>Trees remove 4,315,039 cu. ft of stormwater </li></ul><ul><li>Stormwater savings from trees: $8,639,078 per year </li></ul><ul><li>Trees postpone time of concentration by 20% </li></ul><ul><li>Trees reduce peak flow by 40% </li></ul><ul><li>40% of stormwater infiltrates </li></ul><ul><li>Trees remove 50,689 lbs of air pollutants per year </li></ul><ul><li>Benefits of air pollution removal $124,579 per year </li></ul>
  39. 39. Observations <ul><li>This project assisted to understand the importance of periodical and systematic water quality testing program. </li></ul><ul><li>This system will assist to analyze potential benefits of future BMPs. </li></ul><ul><li>The city could use the GIS layers as a decision-making tool once detailed water quality data is available. By using up-to-date water quality data from the critical locations in Somerville the city could identify which investments would yield the highest potential benefit in water quality improvements. </li></ul><ul><li>Such program will assist to address the problem, define the solutions and in the process increase the potential of recreational use of the urban waterways. </li></ul>
  40. 40. Final Comment <ul><li>Developing a stormwater asset management system works like a hidden treasure, thus providing us with: </li></ul><ul><ul><li>A “ Best Management Practice for our BMPs ”. </li></ul></ul><ul><ul><li>The system helps us understand the different perspectives of stormwater management: </li></ul></ul><ul><ul><li>Engineering, Policy, Economics, Educational, and </li></ul></ul><ul><ul><li>Provides directions for better urban environmental planning while satisfying the various regulatory needs. </li></ul></ul>

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