I do not have any specifc anchor system designs for you, but would like to suggest a few important thoughts:
An anchor is a great safety device and also a great hazard. Make sure that the anchor cannot be inadvertently released when going through a rapids or down a slide. A good system is one that pulls the anchor completely out of the water when up so it cannot catch on anything in the water. Also, never tie the anchor line end to the boat. It is better that the anchor and line are lost versus pulling your craft under the water.

Best anchor design depends on the river bottom. Small, compact Pyramid Anchors work very well on river bottoms of smaller rocks and gravel. Big rocks on the river bottom can eat Pyramids that can not be unstuck. Spike Anchors work best where the river bottom has bigger or irregular rocks. Links to my home made Spike are-- http://i285.photobucket.com/albums/l...n/IMGP0293.jpg and http://i285.photobucket.com/albums/l...n/IMGP0294.jpg

I use both a Pyramid or a Spike---depending on the stream.