Is it OK to throw pebbles and stones in streams, waterfalls, ponds, etc.?

Technically, according to Leave No Trace principles you should leave everything as you find it. Two other related principles would be travel on durable surfaces and respect wildlife. As you intimated, fewer rocks on the trail could perhaps make it less durable and more susceptible to erosion. Obviously throwing rocks directly at an animal (unless for protection) would not be respectful, but I don't know if the underwater life gets agitated or negatively affected in some way by rocks hitting the surface and sinking to the bottom.

Would I stop my child from throwing a few rocks in a lake or stream? Not normally. If I thought it was excessive, I'd get after him and explain why.

posted over 5 years ago

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topshot‭

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Some places have rocks on the shore that arrive there naturally. The effect of a few dozen people per mile people picking up a rock from random locations uniformly distributed along a moving river would be trivial compared with the motion of rocks in and out of the water from natural causes.

A point that hasn't been mentioned, thouh, is that other places have rocks manually placed on them to help control erosion. The more of these rocks get tossed in the river, the more effort someone will have to spend replacing them.

If people picked up rocks from uniformly-distributed random locations, the overall impact in either case would probably be fairly slight. Unfortunately, areas that have rocks manually added to control erosion tend to be more attractive to people wishing to skip stones than the areas which don't.

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supercat‭

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In addition to the other answers here, I would point out that the trail itself may be maintained using a light application of gravel to prevent erosion or excessive runoff.

Removing pebbles from the trail could, over time, degrade the trail itself. I doubt it was a very big deal for your toddler to throw a few pebbles, but if everyone who visited the trail threw a few the trail might be damaged quite quickly. So gently educating your toddler to respect the work of the people who maintain the trail might be the best way to go.

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tbrookside‭

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Nature is not static, it is always in motion.

Let's look at two extremes.

A small pothole full of water on the trail can be completely filled with a couple of handfuls of gravel. Expand this to a small pond at a park and have daily visitors tossing gravel from the path in to the pond, and soon the pond is gone (the path will need fresh gravel as well). In any case, a pond exists because moving water encounters a depression, the water slows and deposits sediments, these sediments eventually fill the depression, and in a few tens to thousands of years the pond is gone.

Niagara Falls is a large waterfall, the erosion is significant, and if a few visitors a day toss a pebble from the path into the falls, the impact is negligible. In another 23,000 years the falls will be gone.

Niagara Falls has moved back seven miles in 12,500 years and may be the fastest moving waterfalls in the world. Source

While there are no absolutes, in general throwing things in still water like ponds and lakes is going to have a more significant impact than nature might have by herself. Tossing a round stone from a river bank into quickly moving water is less of an environmental impact: in all likelihood, the river deposited the rock on the bank, and it has been in and out of the river flow several times.

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James Jenkins‭

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I used to tell my children not to throw rocks in the ocean because eventually the ocean would get full and the earth would flood. Fortunately, they soon recognized that I was simply making a joke about logic. A toddler throwing stones in a stream? What is the nature of the setting? Is this an urban park or a wilderness setting? How likely is the behaviour to be repeated by others? If it is an urban park and the stones are on a gravel path then tossing those stones into the pond might best be discouraged. In a wilderness area? Throwing stones for a toddler is natural human-animal behaviour. Not only does it allow the toddler to develop skills in co-ordination, distance, and place which are critical skills and important for brain development especially in this time of google and 24-7 phones, but it also, and this is important, allows the toddler to develop a sense of belonging in the outdoors. A sense that they are good enough to be in nature. That they are equal in importance to the trees. That they exist not outside nature but within nature. A toddler throwing stones in a stream is completely different than a back hoe ripping into a stream. The difference is not just an order of magnitude. It is a completely different thing. To me it would make more sense to pick up a few stones and join the toddler in his or her pleasure at being outdoors than scold or lecture him or her about correct behaviour.

posted over 5 years ago

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Cracked‭

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Some places are more sensitive than others.

It can be hard to tell whether some innocuous-looking pebbles are a critical habitat for creatures you don't see, but a good guide is to look at how much natural movement of material there is.

The side of a fast-moving stream (even one that's dry right now but frequently floods) or a strongly tidal coast is subject to a lot more movement of rocks than us puny humans can manage unaided. They are great places to take your youngster for this kind of play¹, and wildlife that's disturbed can be assumed to be robust enough to tolerate it.

On the other hand, many still-water environments (even in man-made places such as old quarries) are more vulnerable to this kind of disruption and are probably best left alone unless you specifically know otherwise.

¹ I'm assuming that you have the safety aspect covered; that's not within the scope of this answer.

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Toby Speight‭

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