Reservoirs, and power plant cooling lakes that aren’t designed for public access, just need basic banks designed to withstand erosion. However, recreational and decorative lakes call for more naturalistic and advanced shorelines to mimic what people expect from appealing bodies of water. For some areas, this means building sand beaches like one might find along the coast. Other markets call for vegetated or rocky shorelines that encourage wildlife and waterfowl visitors. There’s no single, best shoreline style, so it’s up to you to match the finished look to the needs of the project.
Choosing a Shoreline
There are many options for covering the accessible shorelines of a man-made lake, including:
- Imported or native sand; which usually rises to the surface around the water’s edge as waves lap away other soil particles
- Rock and gravel cover; offering advanced erosion protection but offering a less appealing surface to recreational users
- Wetlands and marshes that blend the edge of the water into the surrounding soil; are great for wildlife and the water quality but impossible to use for recreation
- Heavily vegetated banks that have grass and other ground covers growing right up to the water’s edge; which can be tricky to maintain if there’s a lot of foot traffic
- Reinforced bank areas covered in native water-growing shrubs like willows and blackthorns; which are not accessible to people but instead designed for intensive erosion control and bank stabilization.
Most large lakes will feature more than one of the main shoreline styles. Recreational lakes tend to feature some maintained sandy beach areas with vegetated and reinforced banks around the rest of the edge. Reservoirs may feature the same gravel or rip rap shores around the entire edge. No matter the style, geomembranes can be installed below the surface to keep materials in place and stop erosion.
Protection from Erosion
The primary function of any shoreline style, or cover material, should be to minimize erosive effects on the banks. Even small and calm lakes will send water lapping at the shores as wind travels across the surface. With the addition of boats and other motorized equipment on a recreational lake, erosion can increase significantly. Rocks and poured concrete embankments offer great protection against erosion, but they’re also unwelcoming to lake users. If the lake is designed for easy access, flexible liners paired with sand or vegetated shorelines provide the best combination of beauty and erosion control. Sand banks and beaches may need routine refreshing with new loads of cover material as the lake slowly removes particles from the surface.
Wakeboarding, Boating, and Other Sports
Lakes used for water sports need the highest level of erosion control on their banks and shores. Boating, jet skiing, rowing, water skiing, and wakeboarding can all create significant wake that destabilizes banks and beaches. Even runners and joggers using the beach may increase erosion if there’s no plan for countering their effects on the shore surface. Vegetative buffers of both water and land plantings, break up the force of each wave and reduce its ability to remove silt and soil. For lakes with high levels of boat traffic or motorboat racing events, large rip rap cover over geomembrane on the banks may be the only option to control severe erosion. Enforcing no wake zones, where boats must stay under a certain speed, will also significantly reduce erosion. Unfortunately, not all visitors can be expected to follow these rules. Unless you can afford enforcement or your lake will be patrolled by local authorities, you’ll need to protect the banks in addition to setting speed limits.
Swimming and Pet Access
Swimmers and lake visitors with dogs, expect soft, clean, easy to access shores for entering and exiting the water. They don’t want to walk over large rocks, through mud, or in prickly water plants to reach the edge. All of these bank types are also better protected from erosion than the soft grassy or sandy banks swimmers prefer. If possible, choose between powered water sports and access for swimming, or at least separate the parts of the lake used for the two purposes. This prevents boat wake from eroding beaches designed for foot traffic instead. It also prevents dangerous accidents from occurring by keeping boats and swimmers from moving around in the same water.
Wind Influence on Large Bodies of Water
Wind doesn’t just create waves on a large lake that lap at the shore. If the banks are made from a fine and sandy soil, wind gusts may lift away silt entirely in large dust clouds. Wind erosion is trickier to deal with than water effects because it’s often unexpected and hard to predict. Many of the same stabilization methods used for dealing with wake, such as keeping banks covered with native plants and using geomembrane liners, can prevent both types of wind-based erosion.
Building Beaches
Because of a high amount of foot traffic during the summer months, artificial beaches around lake edges generally require a lot of maintenance. In addition to erosion control and replenishing measures, most recreational lake managers must also clean the beaches daily, or weekly, to remove any trash that has accumulated from visitors. Sandy beaches encourage guests to bring along food, drinks, and toys that can generate a lot of trash. Even with proper receptacles, a lot of small bits of paper and foil end up mixed into the sand. Before planning a swimming beach on your lake, consider the ongoing maintenance costs. Broken bottles, in particular, create safety hazards. The lake owner can be held responsible if there’s an injury. Artificial beaches work best when there’s an entry fee charged to cover the cost of repairs and maintenance in the down season. If you build an attractive enough lake, you may be able to finance the maintenance costs of the entire body of water just from beach access fees alone.
Vegetation and Natural Growth
Vegetated shorelines tend to offer the best balance of erosion control, visual appeal, low maintenance requirements, and accessibility. Visitors can still swim or bring their pets for a visit if that’s allowed, while there’s no need to constantly comb a beach for trash or dump loads of sand. These banks are nearly as erosion resistant as rock and concrete covered edges, making them a good choice for lakes with water sport traffic as well.
Shorelines can’t be built overnight. In addition to grading and shaping the underlying soil around the edges, establishing vegetative cover and installing shrub-stabilized banks will take months of good weather. Opening a lake before it’s ready for access will only result in costly repairs to restore damaged banks. If you add one of BTL Liner’s geomembranes to your design, you may be able to reduce the time spent waiting for shoreline establishment.
