Anyone who has spent time with kids around water knows the creativity displayed as they build rock dams. Their fruitless efforts to stop flowing water or develop deep pools to splash in results in hours of harmless fun. But are their actions totally harmless? Recently, Bragg Creek Trails was informed about some of the drawbacks associated with this popular pastime, mainly the detrimental effects on native fish populations. Altering the flow of water, or attempting to stop it (or at least slow it down) can negatively impact fish species. Fish need to move freely throughout their habitat to feed, spawn, avoid predators, and find thermally-appropriate water. Obviously, rock dams are an impediment to these movements, placing undue stress on these species. Water levels in streams, creeks, and rivers fluctuate depending on the time of year. During the heat of the summer, water levels typically drop and water temperatures rise. Fish that require cold water to survive will instinctively search for it. Rock dams can actually warm the water by slowing its flow and then preventing fish from finding the coller water they need. The pools of warmer water formed behind rock dams can cause fish to congregate in large numbers. This makes them more susceptible to both predators and anglers. Over time, the flowing water will bring debris to the rock dams, clogging the smallest of spaces, making passage for even the tiniest species nearly impossible. Lastly, the rocks used to make these dams have to come from somewhere. Usually, they're scavenged from the streambed or river bottom. Moving these rocks disturbs invertebrates which can further impact fish foraging habits. Conversely, rocks moved from shore can destabilize the river bank leading to an increased risk of erosion. When looked at collectively, these so- called harmless structures can have major consequences for life within the water. Now, the last thing we want is kids to stop exploring the world around them and connecting with nature. It might just seem like play, but they're studying the flow of liquid and are constantly troubleshooting to improve upon their design. They likely don't even realize it but they're learning at the same time. We also can't underestimate all of the associated health benefits that come with spending time outdoors. So, we think it's best to continue to encourage kids to get wet, get dirty, and simply play outside and if they want to build rock dams, so be it. But when it's time to leave, teach them the importance of dismantling their work so all of their forest friends can keep living healthy lives as well.