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Wind-resistant urban design - PowerPoint PPT Presentation


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Urban Forest Hurricane Recovery Program. http://treesandhurricanes.ifas.ufl.edu. Dr. Edward F. Gilman and Traci Partin. Wind-resistant urban design. Could this have been prevented?. Photo credit: Chuck Lippi. The answer is yes!. Wind-resistant urban design.

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slide1

Urban Forest Hurricane Recovery Program

http://treesandhurricanes.ifas.ufl.edu

could this have been prevented
Could this have been prevented?

Photo credit: Chuck Lippi

wind resistant urban design
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
what design conflicts cause trees to fail
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?
large maturing tree near curb
Large maturing tree near curb

Photo credits: Brent Marable

space is needed for roots to spread
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
soil depth is necessary for root stability
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

lack of open soil space
Lack of open soil space

Root flare is interrupted by curb and sidewalk

open soil space allows root flare to develop
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

roots cut during construction
Roots cut during construction

Step two

Step one

3 x trunk rule

Step three

Photo credit: Andy Kittsley

poor soil conditions
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

slide16
This is a familiar site for many who live in South Florida.

What can be done with shallow, rocky soil?

larger groupings are less damaged
Larger groupings are less damaged

This design did not suffer any tree damage when a hurricane blew through

selecting the wrong species for the site
Selecting the wrong species for the site

Choose small trees for sites where soil space is limited.

what design conflicts cause trees to fail22
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?
wind resistant urban design24
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
existing design situations
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!

install different surface material rock dust
Install different surface material: rock dust

Spread rock dust

Remove slabs

Pack dust tightly

Photo credits:

final product
Final product:

looks attractive and is no longer a tripping hazard

install different surface material porous pavers
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

re routing walk around tree
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
new design situations
How do we make trees fit?

Parking lots

Planting islands

Road medians

Sidewalks

Streets

Buildings

New design situations
designing the right place
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
appropriate soil space
“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

slide38

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

tree growth in structural soil
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

suspended sidewalk
Suspended sidewalk

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

slide41

Suspended sidewalk: Soil cells

This particular system provides structure to support the hardscape, filling in the remaining space with quality soil.

Pavement

Structure

Soil

use alternate surface materials
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
porous paving surfaces
Porous paving surfaces

Porous surfaces are a good design idea for areas prone to flooding:

  • reduce runoff
  • provide aeration to the soil
designing the right place44
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
the goal a healthy urban forest
The goal: A healthy urban forest

Canopy cover

Diversity of tree species grouped together

plant trees closer for canopy closure
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.
grouping vs individual planting
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.

example of sustainable parking lot design
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.
small trees for small spaces
Small trees for small spaces

When planting within 10 ft. of curbing

Plant small or medium sized trees (no greater than about 35 ft. at maximum height)

wind resistant species
Wind resistant species

To get a comprehensive list of wind-resistant species, refer to our website:

(http://treesandhurricanes.ifas.ufl.edu/index.html

do not over plant one species
Do not over-plant one species
  • Restrict one genera or species to < 20% for a few years
  • Develop a list of alternatives for each commonly planted tree
  • Examples of alternatives to live oak:
    • Swamp chestnut, redbay, trident maple, sugarberry, ash, sweetgum, american elm, cedar elm, overcup oak
wind resistant urban design54
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
where to begin
Where to begin…
  • Get the right people involved
  • Set new building ordinances for the community
  • Become a Tree City USA
who should be involved in the planning process
Who should be involved in the planning process?
  • City engineer
  • Landscape architect
  • Urban forester/arborists
  • Builders & developers
  • Planners
  • Parks and Recreation
  • Power companies
  • Homeowner’s Association
  • City or county commissioners
what is tree city u s a
What is Tree City USA?
  • Program started by The National Arbor Day Foundation to promote communities that take care of their trees
  • Provides a framework for starting a tree management program.

More information:

http://www.arborday.org/programs/treeCityUSA.cfm

contact your local county extension
Contact your local county extension!
  • Get information specific to counties across the state

i.e. tree species that grow well in the area, local soil conditions, etc.

  • Cuts time spent on looking up information in half!
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