Botanica Atlanta Landscape Design

Sinkholes, those frightening depressions that appear suddenly in your yard after major rain events, are popping up (perhaps we should say dropping in)  in neighborhoods all over Atlanta and homeowners may be faced with another hazard of recent torrential rains along with flooded basements and crawl spaces, fungal diseases in the landscape and downed saturated limbs.  Whether caused by natural or manmade means, sinkholes must be addressed to maintain a landscape's safety, functionality and beauty.

Source: USGS

Georgia and Florida inherently have natural sinkhole tendencies due to a high percentage of limestone in the substrata.  Limestone is a soft rock and over time underground water movement and geological movement can erode the stone into a semi-solid status.  Heavy rains in turn cause settling of top soil in the spaces created by the reduction in limestone mass.  These are often imperceptible changes however there is great potential for a notable soil depression.

Manmade causes are also common.  Construction debris buried on site frequently leads to sink holes if the builder did not ensure proper grading and soil compaction before selling the property.  Broken water, sewer or gas lines can also create sinkholes.

Before you can properly repair a sinkhole you must first figure out what type of sinkhole you have and how big it is.  Dig beneath the sinkhole at the lowest point, and dig wider than the sinkhole to explore the cause.  If you encounter debris, you have a void that can be resolved with the help of a landscape professional. If you encounter limestone or granite bedrock, broken pipes and or water, you may want to get a city or county authority involved.

For the manmade sinkhole which is less than 3 inches deep, apply topsoil in a 2:1 mix ratio with sand.  Existing grass will grow through this easily or you may choose to seed if there was no lawn above the sinkhole.  Do not seed if there is existing lawn.  If the sinkhole is greater than 3 inches deep, remove the sod carefully, then apply topsoil and compact using a compactor and finally, replace the sod.  If greater than 1 foot of topsoil is required, compaction should occur once per foot of new soil.

If the sinkhole is a natural, substrate problem, remove all organic matter and debris and fill the bottom of the hole with rocks in graduated sizes from large at the bottom to gravel.  Apply landscaping cloth, then cover with sand until level with the top of the subsoil.  Compact, then add topsoil and compact.

Unless your sinkhole is small you should probably have a landscape professional help you assess the problem and suggest solutions.  If you encounter standing water or smell gas, call your city or county authority as well.

Atlanta recently got over 25 inches of rain and many residents experienced the ravages of our floodwaters in some way or another. High volume preciptation created problems with both pooling water and fast moving water, both problems that can be managed in the landscape.

Site grading is the most elemental of drainage strategies homeowners can use to control the flow of water across their properties from areas of undesirable over-saturation to collection areas for later use or to municipal stormwater systems. Generally houses should be sited so that stormwater drains away from the house.

If downspouts create pooling or erode the soil, or if high volumes of water enter from a neighboring property, dry creek beds can be used to direct rainwater off the property or to a collection area such as a dry pond, retention pond or rainwater harvesting cistern. Dry creek beds can be designed and specified to compliment the aethetics of your landscape and add a new dimension to your site vistas.

Photo Credit: Sturgis Rock Solid Solutions

French drains are appropriate for controlling excessive moisture around foundations, where hardscapes and softscapes create pooling and where grade depressions create ponding in undesirable locations. French drains are basically just trenches filled with gravel. Sometimes drainage pipe is installed. French drains act as disguised dry creek beds, and can transport water under turf or other landscape features.

Including native wetland plants in high moisture areas can also control water excesses on site. Winterberry hollies, inkberry, florida anise, willows, red dogwoods, birches, cedars, horsetail, ornamental grasses, lillies, and rose mallow are all species native to Georgia which can withstand or even thrive in excessive moisture.

If the recent rains pointed out site drainage issues on your property, talk to a qualified landscape designer for advice about how to manage drainage, even harness excessive water on your property for asethetic or functional gain.