A rock wall is an attractive, useful and economic addition to any landscaping. You might be able to gather your river rocks from a local dry river or creek bed. If not, buy them and have them hauled to your site. The secret of rock walls that have stood for many years is in the foundation. Anyone with a strong back and some nice rocks can build a rock wall to last for decades.
Dig the area for the foundation of your rock wall with your shovel. Make the hole twice as wide as your wall will be and between 1 to 2 feet deep, depending on the height of your wall. Rake the bottom of the foundation hole smooth.
Throw lots of medium to small rocks and/or scraps of metal and other hard junk into your foundation hole for reinforcement. This will also allow you to use less mortar.
Mix your mortar in your wheelbarrow, combining four parts sand and one part Portland cement. Put water into the wheelbarrow first, then the sand mixture.
Pour your mortar into the foundation and let it harden for a day.
Soak and clean each stone as you use it. Mortar adheres better to wet stones. Set each stone so the flattest side is up. Slant the river rock toward the slope if there is one. Put the larger, longer stones nearer the bottom of the wall so it won't be top-heavy. Lay one layer at a time, trowelling about 1/2 inch of mortar on top of the rocks as each layer is laid. You may need a little more than 1/2 inch in places. Keep the front of the wall as flat as possible. Clean excess mortar from the face of the rocks as you go.
Set in drain pipes, especially in the lower parts of your wall if your wall is set against a slope or will be used as a raised garden.
Set the top stones, or capstones, last from rocks you have been saving. These should be flat, long and as wide as the top of your wall.
Clean your wheelbarrow and tools with water.
Do not use a concrete mix because it has gravel in it and is not suitable for use between your river rocks. If you are building a larger wall and need to haul your rocks, use at least a 3/4-ton pickup truck with plywood laid in the bottom of the bed to prevent damage to your truck. Always wear gloves when handling mortar. The lime content in the mortar has a corrosive effect and will harm your skin. Take care also to not to breathe in dust from Portland cement.