Well, Joy, if you just leave them in the pond, and don't provide a spawning mat or plants or other hiding places, most of them will be eaten.
I have rehomed koi using Craig's List. You could also join Freecycle.com Look for the Houston chapter, and then the chapter in your part of town.
Also, occasionally someone asks for or offers fish on the Houston Pond Society e-group. Right now a Katy lady is looking for koi to replace the ones she lost (all of them!) after the freeze. I have some I'd like to give her (blue ones, too!) but I can't catch the danged things!