Tree Root Damage to Sidewalks and Curbs

Tree roots cause enormous damage to sidewalks and curbs each year, and repair of this damage has been a major cost to cities. In 1975, for example, Hamilton et al. (4) found the annual cost of repairing root-damaged sidewalks to be approximately $27,000 per city for 22 northern California cities. Sidewalk damage is especially serious because cities may be liable if citizens injure themselves on root-damaged sidewalks (3,5). To explore how damage to sidewalks and curbs is related to tree species, tree size, planting-strip width, and soil texture, we studied street trees in cities along the eastern shore of San Francisco Bay in California. These cities have a nearly frostfree Mediterranean climate with annual precipitation of 16 to 20 inches, which falls mostly from October through April. All trees studied were located in street rights-of-way between curbs and sidewalks. The soils consisted mostly of clays and clay loams except for sands in two areas.