Lake Bank Erosion
There are three types of soil loss that occur along lake banks. Any particular lake may experience one or more depending on site conditions. Contact Beautiful Ponds to schedule a site visit to evaluate erosion in your lakes.
Soil loss around a lake isn’t all labeled “erosion”. Here are the three types of soil loss that occur around stormwater ponds like yours.
Bank erosion
The first type of soil loss along lake banks is known as bank erosion. Bank erosion occurs when water flowing down the banks removes (erodes) soil from the banks. The erosion produces gullies where the flow of water down the banks becomes concentrated.
Usually, if gullies are not present, erosion is not occurring and the loss of soil is due to one of the other two types of soil loss. The exception to this rule can be a “hidden” gully. This how it occurs. Occasionally, water traveling from your roof finds a gap in the sod & starts flowing under the sod; washing the soil from under the sod into the lake. The gully is present, but hidden under the sod.
Example of Bank Erosion
Beach Scour
The second type of soil loss along lake banks is known as bank or beach scour. Beach scour is the result of wave action, and generally can occur only on lakes that are sufficiently long enough for wind to produce waves of significant height and duration. Because winds tend to originate from the same general direction most of the time, bank scour will usually be present only along the particular portion of the shoreline where waves are commonly produced. Given our fine, sandy soil, two-inch-tall waves can cause beach scour.
An Example of Bank Scour
This photograph was taken when the lake water level was relatively low. During the summer months, the plants in the beach area are underwater. Installing the right aquatic plants in the shallow area is an excellent way to significantly reduce beach scour.
Bank Settlement – S5 (Super-Saturated, Sandy Soil Settlement)
The third type of soil loss, Bank Settlement is the most common. This type of soil loss is often incorrectly identified as either bank erosion or beach scour. Bank settlement is due to the long-term settlement of super-saturated sandy soils that form the banks of the stormwater ponds.
Bank settlement happens even in areas protected from waves
Super-saturation occurs when soil is submerged for an extended period of time. Once the sandy soil of a lake bank becomes super-saturated, the soil becomes quick (as in quicksand) and literally flows like a thick liquid to the lower area in the middle of the lake. The rate of settlement is directly related to the types of soils that form the banks. Soils with high clay content have good cohesion and will settle at a much slower rate than soils with low clay content. Because the banks of large lakes may be formed of soils with both high and low clay content, the rate of settlement can vary around the shoreline of the lake.
An Example of Bank Settlement
This is also an example of the severe consequences of erosion. The house on the left is a little closer to the lake than the right home. As the lake eroded further, the home was too close to the lake & the owner lost his home insurance.
In this photo beach scour is compounded by bank erosion. Notice the light colored, sandy area in the water. This soil was formerly back yard. Most erosion happens slowly, but when you have more than one type of erosion, it happens faster.
Beautiful Ponds staff are ready to review your erosion issues & formulate a successful plan.