Part 4: Tree Risk Assessment and Management

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Joella Holt
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1 Part 4: Tree Risk Assessment and Management R O C K Y M O U N T A I N C H A P T E R ISA C O N F E R E N C E S E P T E M B E R 2 7 C H E Y E N N E, WY

2 Definition 1: Liability URBAN FOREST MANAGERS ARE RESPONSIBLE FOR THE SAFETY OF PEOPLE AND PROPERTY THAT LIVE OR ARE LOCATED WITHIN THE GREENSPACES OF A COMMUNITY.

3 Definition 2: Negligence THE CONDUCT OF A PERSON OR ENTITY THAT FAILS TO PROTECT PEOPLE OR PROPERTY FROM HARM CAUSED BY IN THIS CASE ELEMENTS OF AN URBAN G REENSPACE. THE STANDARD OF CONDUCT IS WHAT WOULD B E REASONABLY EXPECTED OF A PERSON OR ENTITY.

4 Definition 3: Nuisance AN UNREASONABLE INTERFERENCE WITH THE PUBLIC S RIGHT TO USE AND ENJOY PUBLIC OR PRIVATE PROPERTY.

5 Definition 4: Risk THE PROBABILITY THAT A FAILURE WILL OCCUR AND DAMAGE OR INJURY WILL RESULT.

6 Definition 5: Probability THE LIKELIHOOD THAT AN EVENT WILL HAPPEN. VS.

7 Definition 6: Target FOR A RISK TO BE ESTABLISHED, A TARGET MUST BE PRESENT.

8 Definition 7: Defect A STRUCTURAL PROBLEM RESULTING FROM INJURY, DISEASE, OR POOR ARCHITECTURE THAT MAKES IT MORE LIKELY THE TREE OR BRANCH WILL FAIL. JOE O BRIEN U.S. FOREST SERVICE

9 Definition 8: Hazard A SITUATION THAT COULD RESULT IN INJURY TO A PERSON OR DAMAGE TO PROPERTY. JOE O BRIEN

10 Part One: The Obvious

11 Obvious Tree Defects Canopy Defects Trunk Defects Instability

12 Canopy Defects Deadwood Codominance Attachments with Included Bark

13 Deadwood Die Back: Least Hazardous

14 Stagheading Bigger Hazard, Bigger Issues

15 Codominance Degree of Hazard Dependent on Size

16 Inclusion (Included Bark Attachments) One of the More Predictable Things In Life

17 Trunk Defects Cracks Seams/Ribs Decay: Extent of, Type of Decay with Cavity Opening

18 Cracks in Trunks Undesirable Unacceptable Risk

19 Cracks in Trunks: Internal View Location of this Crack, Decay and Secondary Crack was 20 Feet Above Ground (see previous tree).

20 Seams and Ribs Rib

21 Seam Seams and Ribs

22 Decay: Extent. (Strength Loss) Photo: Dave Hanson

23 White Rots versus Brown Rot White Rot attacks all Cell Materials Some Destroy Lignins and Cellulose, Some Lignins Strength Loss Not Significant Until Late Stages Photo: R. Blanchette

24 White Rot versus Brown Rot Early and Quick Breakdown of Cellulose Significant Strength Loss Photos: R. Blanchette

25 Decay with Cavity and Opening

26 Instability Disproportionate Root Plate Severed Roots Stem Girdling Roots (SGR)

27 Disproportionate Root Plate

28 Photo: Dennis Fallon Severed Roots

29 Stem Girdling Roots

30 Tree Failure in Loading Events For all trees that failed totally, and were located outside of the storms' centers, 32% had 4 inches or more of soil over their first main-order roots and had stem compression from stem girdling roots.* *Storm Damage in Minnesota, , n=1,600

31 Part II: Not So Obvious Defects, Hazards, Risks Trouble-Makers Poor Placement Scores Conflicts Dangerous Liaisons Too Much of a Good Thing

32 I ll Select Trouble-Makers for $200 Decay-Prone Prone to Storm-Damage Culturally Dysfunctional Uh-oh, I Think I Stepped in Something

33 (some) Decay-Prone Trees Hackberry (Celtis occidentalis) Willows (Salix species) Red Oak (Quercus rubra) Silver Maple (Acer saccharinum) Red Maple (Acer rubrum) Basswood/Linden (Tilia americana, cordata) Poplars (Populus species) Grey Birch (Betula populifolia)

34 Silver Maple A Trouble-Maker Photos by Dave Hanson, UMN; Destruction by Jacob Ryg, Rochester

35 Basswood/Linden A Trouble-Maker Photos by J. Ryg

36 Red Oak A Trouble-Maker Photo by K. Sullivan

37 Jacob Ryg Hackberry A Trouble-Maker

38 Prone to Storm Damage Wind Events Colorado Spruce Littleleaf Linden Hackberry Ice Storms: Silver Maple Cottonwood Russian Olive Northern White Cedar

39 Blue Spruce Prone to Storm Damage Photo by B. Johnson

40 Hackberry Prone to Storm Damage Photo by E. Berg

41 Green Ash Prone to Storm Damage

42 Culturally Dysfunctional All Containerized Trees Retarded Root Systems Littleleaf Lindens SGRs Norway Maples SGRs Most Hybrid Elms Mop Heads Hackberry/Coffeetree/Corktree - Codominance

43 Culturally Dysfunctional KY Coffeetree

44 Culturally Dysfunctional Amur Corktree

45 Culturally Dysfunctional Norway Maple Chronically Buried Too Deep and SGR Formation

46 Culturally Dysfunctional All Containerized Trees Deeply Buried, Restricted Root System Pattern

47 Uh-oh, I think I Stepped in Something Actually, it was Ginkgo!

48 Uh-Oh, I think I Stepped in Something! Messy Fruits or Fruits Apples or Large Fruited Crabapples American Plum Walnuts Oaks Amur Corktree Female Ginkgo - Female

49 Nasty, Slippery, Bee-Attracting Fruit Apples Ginkgo

50 Poor Placement Scores Trees vs. curbs, sidewalks Trees vs. sewer, water lines Trees vs. street lights Trees vs. overhead utilities

51 Trees vs. Curbs and Sidewalks

52 Trees vs. Curbs and Sidewalks

53 What Does it Cost?* Cost Types Costs/ Capita Repairs /Tree Ave. Repair Costs % of Total Costs Annual Costs Sidewalk Repair $0.88 +/- $0.36 1:99 $ $3.01/tree Street & Surface Repair Curb & Gutter $0.32 +/- $0.05 &0.45 +/- $0.10 1:151 $ n/a 1:169 $ $1.14/tree *McPherson & Peper, (15 Cities) Coder, 1998.

54 20% of All Tree Removals Due to Conflicts Photo by J. Ryg big surprise

55 Repair Cycle of 5-10 Years if Tree Not Removed* *Coder, 1998.

56 Why Does Concrete Crack And Asphalt only Buckles?

57 Causes of Cracks Soil Bulk Density Weight on Pavement Poor Drainage

58 Concrete Sidewalks Thickness of 4 inches Engineered to Sustain 3000 psi Down-load Engineered to Sustain 330 psi Up-load However. Coder, 1998

59 Failed Concrete Sidewalks Sidewalk elevated 1 inch by a root fails with 60 psi down-load 1 Root Under Sidewalk Photo Credit: Jacob Ryg

60 Why Do Roots Grow Near Concrete (or asphalt)? Soil Oxygen Level Soil Moisture Level Soil Bulk Density Clay Soils Greater than 1.4 g/cm3 Sandy Soils Greater than 1.85 g/cm3

61 Root Suitable Interface of Soil and Curbing

62 Solutions at least partial Suitable Species Pervious Pavement and Modified Base More Space

63 Suitable Species Smaller d.b.h. Minimal Buttressing

64 Species to Avoid

65 Species to Avoid (in narrow blvds) Silver Maple American Elm or lineage Norway Maple Hackberry Poplars Bald Cypress Large Oaks

66 Trees vs. Sewer/Water Lines Photo from Trenchless Magazine

67 Process of Damage Root Tip Enters Radial Pressure Cracks Pipe Roots Proliferate in Pipe Roots Block Roots Collect Sediment Photo: Trenchless Magazine

68 What Does it Cost?* Total Annual Cost for Cement and Sewer Repair = $4.28/Tree 25% of Annual Tree Budget 51% for Sidewalk Repair 17% for Curb and Gutter Average Sidewalk Repair = $500 Accounted for 20% of Annual Tree Removals Coder, Multiple city survey.

69 Causes for Root Damage* Initial Sewer Pipe Defects Excessive Loading Poor Pipe Joints 3 rd Party Interference Tree Species *Randrup, McPherson, Costello, 2001

70 Sewer Line Damage Variables Tree Species Poplars, Willows, Elms, Ash and Birch (in that order) Types of Piping Clay Most Vulnerable PVC, Ductile Iron, Steel, Reinforced Concrete Less Vulnerable

BOULEVARD TREE FAILURES DURING WIND-LOADING EVENTS O N E S T O R M O N E D A Y - O N E C I T Y

BOULEVARD TREE FAILURES DURING WIND-LOADING EVENTS O N E S T O R M O N E D A Y - O N E C I T Y TREES AND WINDS COLLIDE EVERYWHERE NORTHERN WALES WEEK OF 2/10/14 Robert Parry Jones photo NORTHERN WALES