Fall Gardening Project: Dry River Bed

In the arid Southwest, most plants don’t like an abundance of rainfall. Xeric plants such as lavender or rosemary can be damaged or die from too much moisture in the crown or roots. Sometimes, the location a homeowner places a plant affects watering and alters the plant’s ability to thrive as as it should forĀ  the zone in which the gardener lives.

dry river bed
Dry river bed in summer, with blanket flower in foreground and blue mist spirea in back right. The spirea was getting too much water before we began.

Other times, conditions change. That’s what happened in an area near the foundation of our home when we expanded our back patio. We found that excess water from the patio and rain barrel near the edge redirected water during rains. During monsoon season, a blue mist spirea (Cayopteris) and cotoneaster began to show signs of overwatering.

DIY dry river bed
A before shot with Buster waiting in our high-traffic area of grass. The spirea is left foreground and the cotoneaster behind it.
dry river bed
We enlarged our patio and added a few rain barrels. This one was flooding the ground near it when it overflowed. The swamp milkweed we added likes the water.

We needed to divert some water away from the two bushes and recognized the importance of either collecting or directing rainfall. We couldn’t afford a large rain cistern, but we had one natural resource in abundanceā€”rocks. So we built a dry river bed, also called a dry creek bed or dry stream. The project was a way to change up the landscape and divert extra water down to our lawn.

DIY dry river bed
We moved the blue mist spirea up onto a berm built with extra dirt — from another DIY project.

Step 1: Move plants

The first step in our project was to move the plants. We divided the spirea and kept the largest portion to replant; we transplanted two smaller sections on a ditch bank back in our orchard. We ended up removing the cotoneaster, which was beginning to overgrow a path we us regularly and had large areas of rusted, dying foliage.

DIY dry river be and added a Karl Foerster grass.
Our first replacement cotoneaster did not make it. We moved a cactus and penstemon to the new hill as well.

Step 2: Design hills and valleys; test

We next built up a small hill or berm as a new spot for the blue mist spirea and a new cotoneaster bush. This would allow us to control the plants’ watering better. We dug and scraped a river-like trough to help water drain down and toward the grass. It didn’t take much depth to get water from the patio to the grassy area below. Getting the depth and flow right took some trial and error with a garden hose to simulate the rain and made a few adjustments where water backed up.

Testing the flow while we could still lift the fabric if needed.

Step 3: Add rocks

We already had a pile or two of rocks we’ve dug up. And there is no shortage around here. The first step was to cut and lay down black weed barrier, followed by large rocks along the top and side of the dry river to hold the fabric, direct water and add a decorative, but natural effect. This was followed by addition of medium and smaller rocks. We gathered the small rocks throughout fall and winter, sometimes a few at a time, to fill in.

rock river bed
Rocks are much easier to come by around here than water. We lined the sides and bottom with rocks from our property. The large piece of flagstone is a step over the water that runs from the low side of the patio.

Step 4: Plant!

All our hard work was rewarded with a new area for planting. We had the two bushes, and moved a small pine leaf penstemon to a lower part of the berm. We purchased several grasses, some perennials and a few annuals to fill in. Then we got lucky and had a volunteer blanket flower crop up in just the right spot. We stopped the rock design a foot or more from the house in most spots and used pecan mulch around those plants. Here’s why: Rocks reflect sun and heat and my office window is right above the dry river bed area.

Mondo grass
We hope these mondo grasses will grow and spread to cool the wall a little. The mulch is pecan bark. And the new cotoneaster is small but healthy.

Lessons learned:

Pulling out the large cotoneaster and adding rocks has intensified the heat in my office. I know that will ease once the plants grow to maturity. And the heat might be welcome on a cloudy January day. We also lost the first cotoneaster planted. It could have been any of a number of causes, but we likely made a common mistake: not watering enough. I was so concerned with keeping this plant from getting too much water that I failed to account for how much would drain away from its roots and the immaturity of the plant. Our second attempt is going well. It’s also easy to change the flow of water just by placing a rock or two in a certain way. So we check the flow when it rains to look for pooling of water.

We transplanted some grass into the walkway and added two pieces of flagstone.

Overall, we were pleased with the look and function of the dry river bed. The native grass below it turned green earlier than normal and we stopped problems from mud and overwatering of bushes in the area. This is an easy and inexpensive garden DIY project!