Now we all know that swimming requires caution in any water. We shouldn't have to post danger signs to remind folks of common sense along every stretch of Lake Madison's relatively calm 16 miles of shoreline.
USGS topographic map of Walker's Point and gravel pit area, south side of Lake Madison, SD
But Walker's Point seems to be a special case. The moment my dad heard about the drowning on the police scanner, he noted that Walker's Point sits right by old gravel pits. He said there are old excavations underwater that cause undercurrents. This GF&P map appears to support that observation, showing two anomalous pits, 13 and 15 feet deep, west of Walker's Point, just south of Best Point. It's just a few steps from a shallow sandbar to two deep holes. There are no similar sudden deep spots anywhere else in Lake Madison.SDGFP underwater topographic map, western half of Lake Madison, SD
Deputy Tim Walburg and rescue divers reported there was a current of some sort present in the drowning area last Saturday. Water moves very slowly from Lake Madison down to Round, Brant, and on to the Big Sioux, so it's more likely any undercurrent comes from wave action and maybe water temperature differences.
Whatever the cause of the unusual hydrodynamics at Walker's Point, Dylan Nelson and the brother and cousin he helped save from drowning aren't the only ones to experience this hazard. Kristy Nelson says that since last Saturday's accident, a number of people have contacted her to say that they or people they know have experienced similar trouble while swimming in that area. Not that Mrs. Nelson needs any convincing... but GF&P might. Mrs. Nelson has asked GF&P to put up a sign warning of the drop-offs and possible undercurrents, and GF&P has said they will look into it.
To help GF&P look into it, Mrs. Nelson is asking anyone else with stories about close calls off Walker's Point to contact her (nelsokr at gmail dot com) or the GF&P.
Some long-time locals may know the topography and history of Lake Madison, but I've been here in Lake County 30-plus years and was surprised to learn about the hazards off Walker's Point. Increasing numbers of out-of-town visitors and new residents could use a heads-up as well. A warning sign at Walker's Point, maybe even a posting of that underwater topo-map, would be a useful, neighborly reminder that could prevent some future bad news.
p.s.: Game Fish & Parks has underwater topographic maps available for dozens of South Dakota lakes. The maps include data about average depth, surface area, volume, and even the shoreline development index, a ratio that indicates the "bumpiness" of the shoreline. Whether you're a swimmer, boater, fisherman, or just a map nut, the maps are pretty intereesting.