Linda, gravel is the biggest cause of death and of course worst hazard for turtles so avoid it if you can(Ever hear of impaction?) Buy pebbles, preferrably large ones. Moreover, rocks on top of gravel are prone to slide, which could cause suffocation and drowning. Turtles are apt to dig, you know, and I'd lost some this way.
Good thing for big red ears is a log. If you can manage it, find very sturdy, unmoving, large rocks too. But however you make a basking spot, always be careful of rocks because they shift. Hence, drownings.
Logs will keep this from happening.