Fort Oglethorpe is also being required to address the quantity and quality of water runoff of new developments or property that is redeveloped.  We are in the process of adopting the new Post-development Stormwater Management Ordinance for New and Redevelopment.  This ordinance will require that developers meet the guidelines as designed in the Georgia Stormwater Management Manual.

This is a new program that will help prevent additional flooding caused by increased impervious surfaces.  It will help prevent further pollution of our creeks and streams.  The new ordinance requires that the developer of a project take responsibility for addressing these issues before ever breaking ground.  They must submit a plan of action up front that must be approved by the city before any permits can be issued.

Stormwater Management

The Stormwater Runoff Problem

After it rains, some of the water is not able to absorb into the ground so it runs off the land and is called stormwater runoff.  This stormwater flows downhill to the nearest storm drain, stream, river or lake.  In an undeveloped area, most of the rain is adsorbed into the soil and taken up by vegetation, with only a small amount of water running off.  As a watershed is developed, impervious surfaces such as buildings, parking lots, driveways, rooftops and roadways prevent rainfall from infiltrating or absorbing into the ground.  This results in an increase of stormwater runoff which can cause flooding and stream bank erosion.

Stream Bank Erosion

Sometimes controlling erosion seems like a never-ending battle. Precious soil seems to slip away at an alarming rate, and along with it go property values.  While some stream bank erosion is due to natural stream flow, people’s actions speed up the problem when they convert land from wooded land to pastures or even worse commercial areas with lots of impervious surface, without preventing erosion down stream. A large increase in impervious surfaces (paved roads, rooftops, drive ways, parking lots, etc.) added with new development has increased runoff — rain water or storm water that is not absorbed into the soil. The increase in runoff translates to higher stream flows (deeper and faster moving waters) and flash flooding that scours or washes away the stream banks.  In effect, stream banks are becoming unstable and eroding as streams become wider or deeper to accommodate the increased flows.

Major causes

Stream banks are always in a state of fluctuation due to the natural process of erosion, which means that soil is washed loose, transported and deposited in a new location.  However, some of our actions or a change in conditions can increase the rate of and severity of erosion including:

· Vegetation removal. The deep rooting systems of native shrubs and trees help to hold the soil in place.  Removing this woody vegetation leaves the banks unprotected and more susceptible to currents, damage from runoff, and wave action. Replacing woody vegetation with lawns also accelerates bank erosion because the roots of common turf grasses are too shallow to prevent bank erosion.

· Increased stream flows. Stream bank erosion results from the inability of soils and plants to handle increased water flow, which is often related to development as vegetation is removed and replaced with impervious surfaces.

· Wave action from wind. Constant waves and swells created by winds can loosen soil particles on shorelines and cause erosion, especially along points and other areas exposed to wind.

· Overland runoff. If unmanaged, overland runoff may form deep gullies, depositing sediment in a nearby stream or reservoir.

 Effects of erosion

Eroded soil, sand, or gravel that is carried by water is called sediment, and the process by which it accumulates in streams and reservoirs is called sedimentation. In nature, there is a low level of erosion that is a normal part of geological processes, but our actions can increase levels of sediment entering streams which have negative impacts on water quality and stream health.

Sediment is transported downstream by streams and rivers. Some sediment eventually reaches a reservoir where it settles and accumulates. Sediment is also deposited directly into reservoirs by runoff and stream bank erosion. Sedimentation is the largest source of nonpoint source pollution and a serious threat to water quality because it can:

· Fill spaces between rocks and gravel, suffocating aquatic organisms

· Destroy the habitat of aquatic insects and other wildlife in the aquatic food chain

· Release nutrients and toxic chemicals, which lower water quality, promote algal growth, and harm aquatic wildlife

· Decrease the clarity of water and limit the growth of beneficial aquatic plants

· Increase the cost of municipal and industrial water treatment

· Reduce the desirability of water for swimming and other types of recreation

· Fill natural stream channels and cause an increase in bank erosion.

 Erosion control

The best approach to controlling stream bank erosion depends on the severity and cause of the problem. In some cases, woody vegetation and a good riparian or vegetative buffer may be all that’s needed. In other cases, a combination of bioengineering treatments and native vegetation or hard-armoring with rock riprap may be necessary.  Contact the City’s Stormwater Program Manager to find out more information or take a look at the Manual for Erosion & Sediment Control in Georgia.