Urban Forest Hurricane Recovery Program

1. Urban Forest Hurricane Recovery Program http://treesandhurricanes.ifas.ufl.edu

2. Dr. Edward F. Gilman and Traci Partin Wind-resistant urban design

3. Could this have been prevented? Photo credit: Chuck Lippi

4. The answer is yes!

5. Wind-resistant urban design • Design conflicts that can cause tree failure • Design solutions that promote wind resistance - existing design situations - new design/construction • How to take action

6. How often do trees fall down due to poor design?

8. Large-maturing trees within 10 feet of a paved surface, without space designed for root growth Lack of open soil space Large roots cut during construction Poor soil conditions Single specimens (versus grouping trees) Wrong species selected for the site NOT ENOUGH ROOT SPACE! What design conflicts cause trees to fail?

9. Large maturing tree near curb Photo credits: Brent Marable

10. Space is needed for roots to spread roots • Fine roots can be found well beyond the canopy of the tree at full maturity • These roots help anchor the tree under high winds

11. Soil depth is necessary for root stability • Roots need adequate soil depth to anchor the tree under high winds. • Soil should be at least 3 feet deep for large maturing trees

12. Lack of open soil space Root flare is interrupted by curb and sidewalk

13. Open soil space allows root flare to develop • The swelling at the base of the tree (where the large roots meet the trunk) is commonly referred to as the root flare or buttress • The root flare provides balance and stability for the massive weight of a tree Flare commonly 2.5 to 3.5 times trunk diameter

14. Roots cut during construction Step two Step one 3 x trunk rule Step three Photo credit: Andy Kittsley

15. Poor soil conditions • Compacted • Shallow soil – rocky; high water table • Drainage issues • High clay content • Alkaline soil/ Lime rock- inhibits uptake of essential nutrients • Little to no organic matter (i.e. builder’s sand) Photo credit: Jim Urban

16. This is a familiar site for many who live in South Florida. What can be done with shallow, rocky soil?

17. Single specimens vs. grouping trees

18. Larger groupings are less damaged This design did not suffer any tree damage when a hurricane blew through

19. Consider the natural setting for a tree

20. Notice the trees still standing

21. Selecting the wrong species for the site Choose small trees for sites where soil space is limited.

22. Large-maturing trees within 10 feet of a paved surface, without space designed for root growth Lack of open soil space Large roots cut during construction Poor soil conditions Single specimens (versus grouping trees) Wrong species selected for the site NOT ENOUGH ROOT SPACE! What design conflicts cause trees to fail?

23. Where do we grow now?

24. Wind-resistant urban design • Design conflicts that can cause tree failure • Design solutions that promote wind resistance - existing design situations - new design/construction • How to take action

25. Problem: Mature tree with large roots interfering with hardscape. Solutions: Install different surface material Add fill and re-pour walk Bridge over roots Re-route walk Existing design situations CUTTING ROOTS IS NOT AN OPTION!

26. Install different surface material: rock dust Spread rock dust Remove slabs Pack dust tightly Photo credits:

27. Final product: looks attractive and is no longer a tripping hazard

28. Install different surface material: porous pavers To protect the root zone around the existing trees in this parking space at a botanical garden, porous pavers were selected

29. Add soil then re-pour over roots

30. Bridging over roots

31. Re-routing walk around tree • When damaged sidewalks are repaired they can be re-routed around the tree trunks • This can eliminate the need to prune roots that caused the walk to lift

32. Do not cut roots!

33. How do we make trees fit? Parking lots Planting islands Road medians Sidewalks Streets Buildings New design situations

34. Choose the right tree for the conditions of the site Design the right place to fit the trees you want Good design happens in two ways…

35. Designing theright place • Plant trees in the open soil space available • If this is not possible, direct roots toward the open soil • If there is not open space for root growth, design appropriate soil space • Consider groupings vs. individual plantings

36. “Appropriate” soil space At least 1000 to 2000 cubic feet of soil for eachhealthy, large maturing tree Open soil space 3 X wider than trunk diameter at maturity (dbh) to allow root flare development

37. Planting strips in successful designs

38. Structural soilSmall aggregate material (angular rocks ~ 1 in. diameter) with enough soil to almost fill the space between the rocks. Roots grow well in the soil between the aggregates. Illustration credit: Jason Grabosky

39. Tree growth in structural soil • These trees were planted into a strip of structural soil installed in this retrofitted parking lot between the blue arrows • They have performed quite well Photo credit: Jason Grabosky

40. Suspended sidewalk Suspending the sidewalk avoids issues with soil compaction so that roots can spread without interrupting the hardscape

41. Suspended sidewalk: Soil cells This particular system provides structure to support the hardscape, filling in the remaining space with quality soil. Pavement Structure Soil

42. Use alternate surface materials • Materials other than concrete can be used as a wearing surface: • crushed granite • gravel • wood decking • brick-in-sand • porous pavers • porous asphalt • These materials allow oxygen to penetrate the soil and may encourage root growth

43. Porous paving surfaces Porous surfaces are a good design idea for areas prone to flooding: • reduce runoff • provide aeration to the soil

44. Designing theright place • Plant trees in the open soil space available • If this is not possible, direct roots toward the open soil • If there is not open space for root growth, design appropriate soil space • Consider groupings vs. individual plantings

45. The goal: A healthy urban forest Canopy cover Diversity of tree species grouped together

46. Plant trees closer for canopy closure • Trees planted 60-70 feet apart grow large lower limbs due to wide spacing, and require pruning to allow clearance. • Group trees 30 ft. apart to encourage an upright form.

47. Grouping vs. individual planting Larger soil space shared by more trees = healthier trees! This is a sustainable design that will last many years. In a few years, this tree will outgrow the space.

48. Example of sustainable parking lot design • Trees are located only in the buffer strips surrounding this parking lot – trees are not in small islands scattered throughout parking lot. • This provides adequate space for tree roots to grow.

49. Remember: small spaces do not support large trees!

50. Choose the right tree for the conditions of the site Design the right place to fit the trees you want Solutions can happen in two ways…