Reynolds Landing has a few small wave options, though its become overshadowed by some of the newer nearby areas, particularly River Run Park, which will be more fun with enough flows to get Reynolds surfable. You’ll find a wave with a small pile that starts to give up lengthy surfs around 400 cfs.
The South Platte Below Union gives the best gauge here; things are best above 400, but you can surf it lower if you need to.
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Park at Reynolds Landing and walk the park for your options.