Drainage System Our Goal: Promote better projects along the coast that balance the use of Lake Erie as a shared natural resource along with the property owners’ need for lakefront erosion protection and the benefit of access to the lake.
A drainage system installed on or within a bluff or bank is a series of pipes and/or gravel-filled trenches that function to remove excess water. Erosion in the form of slumping or sliding of soils at the top of a bluff is often attributed to excess water within a layer of soil. By installing a drainage system, the potential for slumping of soil is reduced because the top layer of soil is now lighter and drier. Additional instability arises at the boundary of two layers of sediment, typically sand over clay, with movement more likely to occur when water is present at this boundary.
In the case of sand over clay, the water is able to percolate through the sand layer but is stopped at the less permeable clay layer. This in turn creates a situation where slumping or sliding of the soil is more likely to occur. Installing a drainage system, however, will reduce the potential for movement as there will be less water between the two layers. Drainage systems will not directly assist with protecting the toe of the bluff or bank, and are mainly intended for removal of water from the upper part of the bluff or bank.
Drainage systems can include the digging of a trench which is filled with gravel to encourage the flow of water away from areas of lower permeability. The trench is then drained via gravity by a pipe to the base of the bluff.
Subsurface drainage systems are generally not visible except for the pipe exiting the lower bluff. All drainage systems should discharge at lake level or the lowest possible level and include erosion protection at the outlet. This will ensure the drained water does not cause damage to the lower bluff or bank areas. Surface water drainage typically incorporates such systems as roof gutters or driveway drainage. Those systems should be altered to divert water away from the bluff or bank.
Although a drainage system is advised in areas where there are layers of sand and clay, most systems do not function as well within the clay soil. This is because the clay can easily clog the pipes, leading to an ineffective drainage system. When constructing the drainage, consideration should be given to how the soils will interact with the system, and how likely it is that the system will produce the desired results.
To maintain a drainage system, monitoring of the system should occur on a frequent basis. Specifically, look at whether water is exiting the system and if the conditions of the pipes have changed. In the case where water is no longer exiting the system, the pipes may be clogged or may have been crushed due to activities on the upland (i.e. heavy machinery over the pipes). The pipes may need to be replaced should this occur. When the discharge pipes move, fall out, or are broken, the pipes should be replaced with the new pipes extending to the lake to limit any additional shore erosion.
A subsurface drainage system may require professional installation while changes to surface drainage can usually be handled by the property owner.
Drainage Systems Essential Information
Function: Remove excess water within a bluff or bank and reduce the potential for slumping.
Appearance: Subsurface drainage systems are generally not visible except for the pipe exiting the lower bluff. Surface drainage may include trenches filled with gravel.
Materials: Pipes and/or gravel-filled trenches.
Issues: Pipes may be clogged or may be crushed due to activities on the upland.