There are not a lot of natural lakes in Georgia. The majority have been created through the damming of flowing water or by digging a hole and filling it up with water. Sounds easy enough! However, there is a catch: erosion. Running water has a habit of picking up silt and sediments on the way to its destination. As long as that water is flowing, the particles are along for the ride. When it slows down the particles gradually fall out of suspension and settle to the bottom of that lake or pond that was just built.
As the title suggests, silt happens. Erosion and sedimentation are natural processes. Given time, even the most well managed watersheds will experience the depositing of silt, sediments and organic matter in its lakes and ponds. The process takes hundreds of years, but can be accelerated by poor stormwater management practices. A majority of these poor practices originate from construction sites. Despite numerous environmental regulations and required erosion control practices, these sites frequently exacerbate sediment deposition. However, the issue is not just at construction sites. Many lakes experience fill in from their very own banks! Lack of established vegetation or damaged stormwater management systems can lead to large amounts of exposed silts and sediments being washed right into the lake at the bottom of the hill.
This uncontrolled sediment and silt influx into lakes can cause issues with water quality as well as increase viable areas for nuisance plant growth. The shallower the water gets, the more areas become exposed enough to sunlight for algae and other aquatic plant growth. Even when the watershed is well managed, nature will gradually run its course and yield decreasing water depths at all inlets into the lake. That is why it is important to understand a lake’s watershed. A healthy, well-managed watershed leads to a healthy, long-lasting lake.
Sedimentation from erosion of lake banks can be alleviated by stabilization of those areas. Establishing healthy vegetation, repairing issues in the stormwater systems, and implementing rip rap can bring site location erosion to a halt and increase the longevity of a healthy water body. When deposition has reached a breaking point, either due to slow accumulation over years or accelerated fill-in due to poor erosion control methods from upstream sources, the only viable solution to reclaim the lake is dredging. Dredging is the physical removal of silt, sediment and organic matter from the lake bottom to restore initial lake depth and water body volume. This is accomplished by drawing down the water level and bringing in excavators and dump trucks to remove and haul off the unwanted build up. It is an expensive undertaking.
Silt happens. Even the most well-managed watershed will still result in deposition and lead to the eventual need for dredging. Extending the life of a lake by remaining aware of disturbances in the immediate site area as well as activities upstream is key. Taking steps to mitigate and eliminate non-naturally occurring deposition and debris build up will preserve the health and longevity of the water bodies we have created in our landscapes.
