While we’ve used sand for decades to build and replenish the beaches, it is now recognized that sand can have a negative impact on the water quality and overall health of the lake. We are already seeing some of these undesirable effects such as algae blooms, decrease in lake depth, loss of fish habitat and apparent decline in fish population. While sand is not the only cause of these problems, it is the easiest one for us to control – simply by not adding any more of it to the lake. Here are some of the ways that beach sand degrades the lake.
Sand does not stay put. Every footstep on the beach pushes it downhill towards the water and it drifts with the current and wind. When the lake is lowered, sand leaves the beaches and flows with the water toward the middle. A study by the Indiana Division of Fish and Wildlife has shown that exposed sand blows from one spot to another, moves with rain and snow melt and ends up where it’s not intended. Sand that doesn’t drift away eventually works its way into the lake bottom, but even though we may not see it, it’s still in the lake. The sand we add contributes to silting-in, making the lake shallower, and at the same time requiring on-going beach maintenance — and more sand! Shallow water is warmer, supports algae growth and is lower in oxygen, conditions that are detrimental to our fish. According to the New Hampshire Department of Environmental Services, while silting is a geologic process that happens naturally over time, adding beach sand to the natural sediment load hastens this aging and filling-in process.
Beach sand is different from native lakebed soil. A study by the Town of New Hartford, CT. ( http://westhillpond.org/beach-sand/ ) showed that because sand drifts easily in water, it clouds it, preventing UV light from disinfecting bacteria in the lake — a natural process that is necessary for maintaining good water quality. As rainwater and snowmelt run over the beach they pickup this silt, it goes into suspension in the lake, and can be transported significant distances. The smallest/lightest particles are the last to settle, and thus the first to be stirred up by aquatic animals, humans or even wind fetch induced currents or the annual temperature induced turnover. Reduced clarity correlates to reduced visibility, and a reduction in disinfection of pathogens by ultraviolet light and in studied cases, increases in presence of microbial pathogens. In addition, a study done in York County, Me. found that a decline in lake water clarity caused a noticeable decrease in the value of surrounding homes.
According to the Tip of the Mitt Watershed Council in northern Michigan,
http://www.watershedcouncil.org/learn/beach-sanding/ deposited sand has major biological impacts on the lake ecology. Sand deposited and drifted along the shore and lake bottom can smother bottom-dwelling algae and invertebrates, reduce the amount of aquatic and shoreline habitat for fish and crayfish, destroy spawning and nesting sites for reptiles and amphibians, and disrupt the food chain. Fine sand particles suspended in clouded water may clog the gills of our lake fish that are not adapted to a sandy environment. This threatens our fish.
Beach sand may contain a number of contaminants that will wash into the lake water changing its natural chemistry. As an example, New Hampshire Department of Environmental Services reports that “iron-rich sand can encourage the growth of iron bacteria that create rust-colored slime deposits and oil-like films on the sand as they oxidize the iron.” If the sand contains phosphorus, a nutrient that supports plant growth and a major contributor to the decline of lake quality, it washes into the lake essentially fertilizing it. According to a study funded by the Maine and US Departments of Environmental Protection, one pound of phosphorus can produce tens of thousands of pounds of algae! As the lake becomes shallower from erosion and silting, there is less volume of water in which these toxins and other contaminants can be diluted. Sand is not the only or largest source of contamination in the lake (bigger culprits are run-off from our septic systems, roads and lawns), but it contributes — and it is something we can control easily.
There are alternatives to beach sand that cause less damage to the lake ecosystem and water quality. These alternatives provide a more stable beach than sand and if done properly will require less routine maintenance. Before proceeding with any one approach it’s a good idea to understand the unintended and unanticipated consequences that our decisions may have on the lake in the future. Regardless of what material we use to construct our beaches, it is universally acknowledged that they should be located in places where the prevailing wind and currents will not contribute to beach erosion. Careful planning, engineering and construction with the right materials can result in beaches that will last many years without degrading the lake or requiring extensive maintenance and repeated lake draw-down.
By controling the use of sand on our beaches we can reduce the amount of phosphorus we add to the lake, help to prevent additional silting and maintain water depth, temperature, clarity and quality. This will help control algae and weed growth as well as help restore the natural chemistry of the lake, something that is important for fish and other invertebrates that call RBL home. The lake is our community’s greatest asset – let’s keep it healthy.