By Clint Calhoun
My last few articles have focused on the lake and specific terminology that is used in the world of limnology that is advantageous to know when talking about different management aspects of lakes. This month, I am going to deviate slightly from that course. I’m still going to talk about the lake, but in a slightly different context due to an enormous event we experienced very recently and that was Subtropical Storm Alberto.
If you have lived or worked in Hickory Nut Gorge for any length of time, you know that we occasionally get storms of Biblical proportion (at least in our finite minds). Since 1992, when I began my career in the Gorge, there are specific storms I remember that were monumental in the impact they each had in the Gorge due to the damage they caused in the area and the impact they had on the lake. Tropical Storm Beryl dropped seven to nine inches of rain in a 24-hour period and caused major washouts in Chimney Rock Park as well as a major landslide in Chimney Rock Village. The Flood of ’96, which some have called the biggest flood since the Great 1916 Flood, came from a low pressure system that stalled over the area due to the advance of Hurricane Fran which would make landfall one day later (incidentally we received no rain from Hurricane Fran). That storm dropped 11 inches of rain in two hours; 17 inches in 24 hours. Landslides occurred all throughout the Gorge, washing Hwy 64/74A out just west of the Esmeralda Inn. It also dropped an unbelievable amount of sediment into Lake Lure which all had to be removed, to the tune of $1.2 million (thank you FEMA). Since then we have had Hurricanes Frances, Ivan, and Joan. Last year we had Hurricane Matthew. These are the storms that stick out in our minds due to the damage and impacts that have resulted.
So what does a flood do to the lake? Of course the most obvious thing is it introduces debris, and lots of it. A lot of people have asked me if all the debris came from the Party Rock Fire and the answer is mostly no. Very few of the pieces of debris ending up in the lake have any signs of burning. The debris is mostly what accumulates in the river and its many tributaries over the 94 square mile watershed. Some of the woody debris is from beaver dams that have washed out in small streams, way upstream of Hickory Nut Gorge. Other debris is from residential property on the river. The debris size is everything from twigs to large trees. In addition to natural debris, we also find a lot of trash, plastic in particular (the single largest human-made pollutant in our waterways), and the occasional washed out porch or creekfront deck.
All this debris creates a huge mess that accumulates in the lake. Under normal circumstances, some woody debris can be beneficial in the right places as it can provide some structure for fish habitat, but in a recreational lake where swimming and boating is the primary use, it makes things very dangerous. Sometimes those dangers are hidden because some debris becomes so waterlogged that it floats just beneath the surface but could impale a water skier if he or she were to fall on it. This why the Town closes the lake, so that there is ample opportunity to remove as much of the large, dangerous debris as possible, making the lake much safer.
Another issue that large storms create has to do with the contents of the storm runoff that infiltrates and fills all of the waterways. That storm water has lots of nastiness in it. Think about all of the gasoline, oil, antifreeze, and anything else that is deposited on roadways and driveways. Think of all the riverfront yards where pets have done their business and owners didn’t clean up after them. What about all the resident Canada geese the Town deals with and their waste? Do wild bears poop in the woods? Well, that’s all in there too. Storm water is a toxic stew of all different kinds of contaminants, including pesticides and herbicides. This all has a huge impact on water quality in the immediate aftermath of a storm. Fecal coliform levels often increase to unsafe levels during storm events due to flooded septic tanks and drainfields. Sometimes sewer lines upstream of the lake can break and their contents end up in the lake. I don’t say all this to discourage anyone from using the lake, because generally Lake Lure is a high quality body of water. The point is, immediately after a large storm event, users are encouraged to be cautious if you choose to be in the water, because it is nasty and there’s stuff in there that you really don’t want on your skin. A good rule of thumb is to wait until the water is clear again before swimming, wading, or other in-water activities.
The last big impact I want to mention is sediment. Sediment is the single largest pollutant in streams throughout the country and it exerts one of the largest economic strains due to the difficulty of removing it from lakes and reservoirs. Every large storm that we experience in the Upper Broad River Watershed has the potential of introducing over 30,000 cubic yards of sediment into the lake. That sediment, which consists mostly of sand and silt, can clog navigational routes to Washburn Marina Bay. It fills in critical spawning areas for different fish species. It impacts the native freshwater mussel species we have in the lake (did you know we have freshwater mussels?). Large amounts of sediment can also eventually reduce the amount of head pressure needed for hydroelectric generation, so it’s a big deal. Unfortunately, sedimentation is the one pollutant the Town has the least amount of control of because the majority of it comes from further up in the watershed. While some comes from residential development, a lot is just natural deposition in the small streams and tributaries leading to the river. Sediment loads are enhanced during large rain events when catastrophic slope failures occur resulting in landslides.
Flooding has huge impacts on the operation of Lake Lure and there are certainly more than what I can point out here in this article. Lake management is a complex game that has a lot of moving parts. In order to do it right, a lot of preparation and planning is needed to anticipate the threats to operation, prioritize the needs, and put together an action plan in the aftermath so that lake use can return to normal as quickly as possible. My hope with this article is to provide some explanation as to what floods do to our lake and why the Town is required to take certain actions in the aftermath. Until next time!
Clint Calhoun is a naturalist, biologist and Certified Lake Manager and has worked in Hickory Nut Gorge for over 20 years. He is currently the Environmental Management Officer for the Town of Lake Lure. Check out Clint’s blog at http://clintcalhounadventures.blogspot.com.