Weather and Trees

by Buck Abbey, ASLA, Robert Reich School of Landscape Architecture, Louisiana State University

Large crowned trees should not be planted under or near utility wires, nor too close to buildings and other structures. These "victim" trees are in Mandeville, Louisiana following tropical storm Isaac. Mandeville, near the shores of Lake Pontchartrain, was one of several communities in St. Tammany Parish deluged by floodwater from Isaac's storm surges. For this community, the flooding was worse than Katrina.

Recent hurricanes, including Superstorm Sandy, which ravaged the east coast recently, point to a serious flaw in the landscape codes that should be addressed by planning departments in cities and towns across the country. The flaw results in residents of towns and cities in hurricane susceptible regions from understanding the storm resistance of various species of shade trees and how they handle heavy winds, flooding, ice and storm tides. This lack of understanding results in many trees coming down that should have been removed prior to the strike of a storm.

It is important to recognize that community tree laws and landscape codes are the proper forum for public tree policy. Communities express in their tree laws, landscape codes and development regulations their official recognition of trees as an essential part of the community fabric. These codes, however, rarely state any policy toward trees and storms.
Why has this been overlooked? Perhaps code writers see storms as "acts of God," i.e., "it's out of our hands," and have failed to see specific tree codes could mitigate storm damage to community trees.

Tree ordinances are very useful in educating the general public about the inherent characteristics of various species of trees. The can also be used to teach people which trees are more storm resistant, and which tree species tend to fail. Tree laws can differentiate between native trees, disease prone trees, long-lived trees and trees that break and get uprooted in hurricane winds. Such codes simply identify which trees are likely to stand up to storms, and which ones are likely to fail.

These hardy trees in Ocean Springs, Mississippi survived tropical storm Isaac. Some tree species are simply more brittle than others, which is why some city ordinances prohibit or discourage planting of willows, box elders, Lombardy poplars and silver maples.

Weather and Trees
City tree ordinances must also address other climate effects: flooding, drought, ice, disease and climate change. Community tree laws or landscape codes in coastal regions of the country should address the impact of high winds or potential storm damage caused by colliding weather systems on neighborhood urban forests.

A publication from the U.S. Forest Service based upon research conducted after Katrina, Storms Over the Urban Forest: Planning, Responding, and Regreening"?uA Community Guide to Natural Disaster Relief (edited by Lisa Burban and John Andresen, 1994 second edition) positively states tree ordinances do not take into account such large storms. They do not address actions that could be taken before such storm arrive, nor do they address poststorm clean up, repair and response.

No tree ordinances within the coastal regions of this country are hurricane responsive! No community tree law from Texas to Virginia has been found that properly sets forth public tree policy for hurricanes.

Missing from the Codes
No tree ordinances within the coastal regions of this country are hurricane responsive! No community tree law from Texas to Virginia has been found that properly sets forth public tree policy for hurricanes. No contemporary tree ordinance sets standards for storm training trees to be more wind resistant. No standards have been drafted to maintain the urban forest to allow that forest to successfully withstand a storm's assault. In fact, most of the trees that come done in storms should have been removed before the storm, since most trees that are damaged show signs of stress, decay, root zone problems or structural failure in advance. Maintained trees are often "survivor trees."

No tree policy sets standards or preferences for the selection, planting and proper care of suitable species of trees that have a reputation of being more storm resistant. No tree policy exist that bans unsuitable tree species that have been described as "victim trees," or those most likely to be damaged by rogue storms. Even "spacing standards," based upon tree height and distance from buildings, have not been addressed in the codes. This can prevent the sudden act of trees falling on houses.

Ideas for the Codes
There are other aspects of storms and trees that might be mentioned in community tree ordinances. They might include tree standards that recognize the importance of preserving hurricane groves, urban forest buffers and tree canopy within public parks and community open spaces. In addition, community tree ordinances might set standards for better planting location selection, limits for "fall zones," hurricane resistant species selection and recommendations for sizes, structural supports, annual or seasonal maintenance routines and arboricultural storm preparation pruning specifications.

Finally, community tree ordinances might even address the control community poststorm, clearing and clean up procedures, disposal, recycling and cost with the objective of strengthening the urban forest to better protect human life and property.

It is time that communities across the nation start to look at revising public policy toward trees in community tree ordinances with respect to weather.