A neat trick for getting more purchase out of your anchor (larger boats and/or faster currents) in a river type setting, is to use two anchors in series.

For example (working back from bottom to the boat), a claw anchor, 2-4' length of chain, and then a standard DB lead anchor attached to the mainline. Although the setup is a bit unwieldy, you can often get by with less weight using this rig than a single anchor. The lead and chain keep the primary anchor on the bottom and prevent it from levering out and/or giving it more purchase.

Like Stam, this setup works well on a variety of bottom types.