Trees and Sidewalks - Who Exploits Who (NA-98-0417)

Study to determine how rapidly trees exploit sidewalk block cracks.

Cities have often been taken to court when a citizen trips over a raised sidewalk. Trees, in turn, are often blamed for the raised sidewalks. This study was undertaken in the belief that understanding the interaction between trees and sidewalks will enable city foresters to better manage trees in urban environments.

Sidewalk blocks chosen at random in four soil types with and without trees were evaluated.Sidewalk repair histories varied by soil type or complex in Cincinnati OH. Failure of sidewalk blocks wassimilar for blocks with and without trees for the four soil complexes studied.

Sidewalk failures often start as a crack between blocks. Sidewalk are a stretch of a brittle concrete with designed break points. The rooting environment under sidewalk cracks is conducive to tree root growth. Growing conditions favorable for root growth lead to roots exploiting cracked sidewalk blocks.

Four genera of trees were evaluated to determine how rapidly they exploit sidewalk block cracks. Gleditsia exploits cracks more quickly than Zelkova or Koelreuteria. Quercus took longer to exploit cracked blocks than the other three genera studied.

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