The design of the features outside of the water in your pond can be almost as important as those under the surface. There are some key features to out-of-water design that will keep your pond younger, longer.
Ponds will fill in over time. It is nature’s goal to fill in every low spot with soil and rocks from higher ground. This, unfortunately, is the natural progression of any pond. Ponds will fill in with both organic and inorganic sediment which will diminish the depth of your pond through the years.
Organic materials, such as leaves, grass clippings, duck and geese waste, dead plants, etc. can both increase the oxygen demand in your pond as well as fill in the depth. Through the natural process of decomposition, the organic material can be removed without dredging. However, it is still a good idea to prevent as much organics from entering your pond as possible.
Inorganic material, such as sand, silt, and rocks will fill in your pond over time and the only way to remove these is to dredge the pond, which is a big expense and a lot of work. To keep your pond young and deep, it is imperative to keep as much of the inorganic material from reaching the water as possible. There are a couple easily created design features that will help in this process.
Designing and building an earthen berm around the edge of your pond is a great way to prevent a lot of debris from entering the pond. Ponds, naturally, are in the lowest areas. Therefore, rainfall runoff will flow toward them, carrying both organic and inorganic material into your pond. A berm, or ridge, around the edge of the pond will prevent much of this debris from entering the water and trap with it, all the organic and inorganic material in that runoff.
Allowing grasses and other vegetation to cover the berm will also help its retention of the water and debris. Remember, if you mow the areas around the pond, keep as many of the grass clippings out of the water as possible to prevent more organic loading into the pond.
Adding Rip Rap, or large, coarse rocks along the shoreline or spillway areas will help with erosion control to keep your shoreline and bank intact, as well as prevent slumping of the shoreline back into the pond. The large rocks take the brunt of any wave action or force from heavy rain and prevent the softer materials along the shoreline from running back into your pond.
Vegetation itself can act as a great filter for ponds. Planting thick vegetation along any area where surface water can enter a pond will help prevent both debris and nutrients from entering the pond. The vegetation will physically stop or slow the introduction of debris and trap it within the buffer. It will also soak up many of the nutrients that are contained in the runoff before it enters the water. This is especially important in farming areas or in areas where lawn fertilizer is used heavily.
Aquatic plants take a fraction of the nutrients to grow as terrestrial plants do, so even the smallest amount of nutrients added can cause high aquatic plant growth. If you need to fertilize your lawn, try to limit the Phosphorus or the P in N-P-K mixtures as this is a limiting nutrient for aquatic plants.
These buffer areas also help stabilize the soil and prevent erosion from high rainfall as well as wave action along the shoreline. Providing excellent wildlife habitat is also a side benefit to these buffer areas.
When deciding on which plants to put in your vegetative buffer, choose native species, and of those species, try to choose ones that use high amounts of nutrients. Consulting with a local lake manager, DNR agent or Extension agent can help you decide what is best in your area.