Background

Whether discussing canopy protection or healthy streams there is very little understanding of the current environmental dynamics that are at play in Sandy Springs. The City of Sandy Springs, like most municipalities, is simply not set up to perform environmental analyses. Although the City has an arborist – the responsibilities are focused on environmental compliance not environmental investigation. On a similar track the City has a storm water group but their primary responsibility is to maintain, repair and replace the pipes in the City’s drainage system – not on scientific analysis of watershed health.

Below are recommended steps that the City will can take to understand the environmental dynamics associated with canopy and watershed health as well as formulate appropriate public policies.

Environmental Dynamics of the Sandy Springs Canopy

There are actually three types of canopies that collectively influence the environmental dynamics of the Sandy Springs Forest. The following sections sketch the importance of the canopies in each area.

The residential canopy. The U.S. Forest Service estimates that approximately 2/3 of the canopy of an urban forest is located in the residential areas of a city. In the case of Sandy Springs the vast majority of forested land is in our yards. The importance of these canopies lies in the ecosystem functions they perform such as carbon storage, interception of rainfall, cooling of the understory and streams and filtering of pollutants from the air that we breathe. For these reasons the health of the residential canopy is a major determinant of the overall heath of the Sandy Springs Forest. Below are the major natural and man made threats to the residential canopies.

• Natural threats to the residential canopy. Invasive species such as ivy, privet and kudzu are the primary natural threats to the residential canopy. By harming the health of trees these invasives can also reduce a canopy’s ability to perform necessary ecosystem functions.

• Man made threats to the residential canopy. Residential housing stocks have lifecycles and Sandy Springs is undergoing an historic residential re-development “wave.” The current tree ordinance requirements are inadequate and the ESS has provided the City with a detailed plan to reform the tree ordinance so that canopies can return to their natural state in the shortest period possible .

The commercial canopy. The importance of the commercial canopy is often minimized but it should not be for a number of reasons

• A major study in Ann Arbor, Michigan linked the loss of tree canopy to specific respiratory diseases.

• The emergence of technologies such as silva cells now allows trees in commercial areas to thrive despite the generally harsh environments of commercial districts.

• The re-development of commercial properties offers a mechanism for re-introducing trees into the urban environment.

• Green commercial districts are more attractive to potential shoppers.

The Park Canopy. Sandy Springs has a number of parks that are protected from residential and commercial re-development including East Palisades, Island Forde, Lost Corners Preserve, and when constructed, the Old Northside park. By comparing the canopy coverage and the level of associated eco-system functions of the park areas to those in the commercial and residential areas we can roughly judge the impact of development on the Sandy Springs forest.

Using Satellite Imagery and GIS Software to Assess the Environmental Dynamics of the Sandy Springs Forest

Environment Sandy Springs is recommending the use satellite imagery and GIS software to:

• Assess the impact of residential re-development on the canopy of the Sandy Springs Forest and take appropriate action.

• Identify and map the ecological habitats and corridors in the Sandy Springs forest so that the City can steer development away from those areas.

• Identify and map residential and commercial areas where the canopy is thinning, either through natural succession or man made activities and initiate tree planting efforts.

• Assess whether the community canopy is think enough to cool the temperatures of the creeks and streams of Sandy Springs streams and thereby contribute to healthy streams.

The City can also require the use of such techniques silva cells (on-site run-off filtration) or the equivalent to allow trees to thrive when planted in the relatively hostile environment of a commercial district

The Environmental Dynamics of Sandy Springs Streams

Background

Assessing the health of streams is even more difficult than assessing the health of tree canopies. Much of the information regarding stream health has been collected by the State of Georgia and different state organizations have different water quality sampling standards. For example, organizations interested in the biological health of the streams may be more interested in an Index of Biological Integrity because the health of aquatic life forms is sensitive to the overall health of streams. An organization more interested in the chemical composition of streams would be more interested in tests designed to quantify the levels of fecal coliform, mercury, or other elements in streams.

What We Know

In 1991 the State of Georgia compiled its initial list of impaired (polluted) streams and the major Sandy Springs streams (Nancy Creek, Ball Mill Creek, Long Island Creek and Marsh Creek) appeared on that list due to excessive concentrations of fecal coliform. Later, during the early parts of this century, Long Island Creek and Nancy Creek were additionally cited for impairments to the habitat of the fish community and later Marsh Creek was cited for the same impairment. Because some fish and aquatic life forms are sensitive to pollution in the streams, the Index of Biological Integrity is often times used as a measure of overall stream health.

The common historical thread in both the pre and post 1991 periods is the growth of impervious surface in the watersheds. Not only do impervious surfaces wash chemicals and waste into streams but they also promote an increase in stream sedimentation that impairs aquatic habitats and ultimately the health of steams.

Healthy Streams Task Force

Due to the fragmentation of water quality data Environment Sandy Springs urges the City to establish a Task Force to analyze and document the environmental conditions in the impaired streams of Sandy Springs. Conceptually the City could accomplish this goal by working with Georgia Adopt-A-Stream and EPD to devise a comprehensive water sampling strategy that includes tests for fecal coliform and the Index of Biological Integrity working with volunteers, under the supervision of the Georgia Adopt-A-Stream, to collect the pertinent data.

The task force would be able to utilize the City’s Environmental Modeling database to identify locations where a reduction of impervious surface would improve the quality of streams and then document approaches as to how this goal could be achieved.