low impact development

1. low impact development strategies and techniques jennifer j. bitting, pe the low impact development center, inc. june 2008

2. hydrologic analysis • low impact development (lid) site planning strategies • lid best management practice selection outline

3. hydrologic analysis • lid hydrologic considerations • lid hydrologic evaluation steps

4. Post development Q Pre-development T Runoff Hydrograph hydrologic considerations • runoff volume control • peak runoff rate control • flow frequency/duration control • water quality control

5. hydrologic analysis • lid hydrologic considerations • lid hydrologic evaluation steps

6. hydrologic evaluation steps • delineate the watershed and microwatershed areas • determine design storm • define modeling technique to be used • evaluate predevelopment conditions (baseline) • evaluate site planning benefits • evaluate lid practice benefits • evaluate supplemental needs

7. hydrologic analysis • low impact development (lid) site planning strategies • lid best management practice selection outline

8. lid site planning strategies • define development envelope and protected areas • reduce limits of clearing and grading • use site fingerprinting • use drainage as a design element • minimize impervious areas • disconnect impervious areas • increase flow path length

9. define development envelope and protected areas

10. reduce limits of clearing and grading

11. use site fingerprinting • place buildings in areas of poor draining soils • save soils that drain well for groundwater recharge

12. use drainage as a design element Source: “Art for Rain’s Sake,” Landscape Architecture Magazine, September 2006

13. 82.35 acres of public street 53.32 acres of public street 35% difference • alternative roadway layout • narrow road sections • reduce sidewalks to one side of the road • reduce on-street parking • reduce rooftop area • design driveways to be: • shared • narrow • short • permeable minimize impervious areas

14. Source: Seattle Public Utilities http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/Natural_Drainage_Systems/Street_Edge_Alternatives/SPU_001805.asp • alternative roadway layout • narrow road sections • reduce sidewalks to one side of the road • reduce on-street parking • reduce rooftop area • design driveways to be: • shared • narrow • short • permeable minimize impervious areas

15. alternative roadway layout • narrow road sections • reduce sidewalks to one side of the road • reduce on-street parking • reduce rooftop area • design driveways to be: • shared • narrow • short • permeable minimize impervious areas Source: Seattle Public Utilities http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/Natural_Drainage_Systems/Street_Edge_Alternatives/SPU_001805.asp

16. alternative roadway layout • narrow road sections • reduce sidewalks to one side of the road • reduce on-street parking • reduce rooftop area • design driveways to be: • shared • narrow • short • permeable minimize impervious areas Source: Seattle Public Utilities http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/Natural_Drainage_Systems/Street_Edge_Alternatives/SPU_001805.asp

17. alternative roadway layout • narrow road sections • reduce sidewalks to one side of the road • reduce on-street parking • reduce rooftop area • design driveways to be: • shared • narrow • short • permeable minimize impervious areas

18. disconnect impervious areas • disconnecting roof drains and directing flows to vegetated areas • directing flows from paved areas to stabilized vegetated areas • breaking up flow direction from large paved surfaces • encouraging sheet flow through vegetated areas

19. disconnect impervious areas • disconnecting roof drains and directing flows to vegetated areas • directing flows from paved areas to stabilized vegetated areas • breaking up flow direction from large paved surfaces • encouraging sheet flow through vegetated areas

20. increase flow path length • maximize overland sheet flow • lengthen flow paths • increase vegetation • minimize slopes • increase surface roughness

21. increase flow path length • maximize overland sheet flow • lengthen flow paths • increase vegetation • minimize slopes • increase surface roughness

22. increase flow path length • maximize overland sheet flow • lengthen flow paths • increase vegetation • minimize slopes • increase surface roughness

23. increase flow path length • maximize overland sheet flow • lengthen flow paths • increase vegetation • minimize slopes • increase surface roughness

24. hydrologic analysis • low impact development (lid) site planning strategies • lid best management practice selection outline

25. bioretention • filter strips • vegetated buffers • bioswale/grassed swale • rain barrels • cisterns • green roofs • porous pavement lid bmps

26. bioretention source: http://www.artfulrainwaterdesign.net/projects/ source: http://www.cuyahogaswcd.org/grantfunded-raingardens.htm

27. green roofs source: http://www.thisoldhouse.com/toh/photos/0,,1599531,00.html intensive extensive source: http://www.wsud.org/Pic_Pages/Green_roofs.htm

28. vegetated buffers source: http://www.sf.adfg.state.ak.us/SARR/restoration/techniques/intro.cfm

29. cistern source: http://www.tfssolar.com/134/sonora-co-housing-residence/

30. rain barrel source: http://johnwesleymillercompanies.com/tucson-water.html source: http://www.iaswcd.org/district_tools/PWQ/temp/PWQ/PathwayBarrel.htm

31. bioswale / grassed swale source: http://www.wbdg.org/resources/lidtech.php source: http://www.fceo.co.franklin.oh.us/images/Bioswale.jpg

32. porous pavement source: http://www.metrokc.gov/kcdot/roads/eng/lid/militaryS272/porousconcrete.cfm source:http://www.hort.cornell.edu/UHI/outreach/index.html source: http://www.paving.org.uk/permeable.php

33. vegetated filter strip source:http://www.wsdot.wa.gov/Environment/WaterQuality/Research/Reports.htm

34. lid best management practices selection • define hydrologic control required. • evaluate site constraints. • screen for candidate practices. • evaluate candidate bmps in various configurations. • select preferred configuration and design. • supplement with conventional controls, if necessary.

35. define hydrologic control required • runoff volume • peak discharge • frequency and duration of discharge • groundwater recharge requirements • water quality goals

36. evaluate site opportunities and constraints • space required • soil type • slopes • depth to groundwater • proximity to foundations

37. select practices • technical feasibility • economic considerations • construction • maintenance • waste disposal • social aspects • shade • noise reduction • environmental impacts • air pollution

38. evaluate bmps in various configurations • check the combination of bmps for compliance with hydrologic goals • adjust the number and size of the bmps until the hydrologic goals are met

39. lid best management practice selection • define hydrologic control required. • evaluate site constraints. • screen for candidate practices. • evaluate candidate bmps in various configurations. • select preferred configuration and design. • supplement with conventional controls, if necessary.

40. three aspects of lid • hydrologic analysis • lid site planning strategies • lid best management practices establishes the goal uses site features to achieve the goal adds additional measures to meet the goal