Gardening on the Moon ( GOTM )

Written by Jeff

While the Sonoran desert would be glad for any rain it could get, large amounts of water wreak havoc with the habitat creating large areas of erosion. Streets flood easily and mud washes onto the roads. During our first summer in Cave Creek, we had a deluge which covered parts of 53rd St. with one to two feet of mud. All but the largest vehicles had to pull to the side of the road and wait until the road was cleared the next day.

We didn’t live on 53rd St., but it is the only access to the road on which we do live so I parked my car and began to trudge through the mud. Luckily, a large truck came by and offered a ride. I was very grateful.

The next day we examined part of our front yard and noticed that one corner had been overrun with mud and it appeared that the river rock had been washed away. We later discovered that it was just buried under the pile of mud. This is a low area of our landscape and parts of it had eroded severely exposing the roots of a couple of Palo Verde trees. I didn’t want these trees to die and I wanted to avoid a repeat of the mud bath. I knew that I had only one choice and that was to build a wadi or dry riverbed. Of course, it would only be dry when the water is not running.

It is often helpful to “invite” the water to take a certain path rather than have it find its own way. What I hoped to do was construct a prepared riverbed that would encourage the water to flow in a certain direction and leave the other areas without much running water, debris and mud.

NOTE: In the interim, I worked with several ranch hands and restored the dirt around the trees so their roots were not exposed. Several tractor loads of soil mixed with horse manure did the trick. Of course I did have to get changed in the garage after this!

The Problem

Water was running downhill across several properties and funneling into this one corner of my property. The slope of the land continues to run downhill well beyond our yard so there is a natural tendency for the water to run towards our street and lot. I needed to change the course of the water; not stop the water, just change the path and slow it down. I wanted to usher the water towards the paved street which can withstand the flow without any erosion. The water would then dissipate as it ran down the paved road.

The Plan

The Plan was to purchase boulders to create a horseshoe-shaped structure in the corner of the property so that the arc curved inward toward the house and the ends were closer to the street which was the source of the water; much like an upside down omega. This would accept the water, but then throw it back out to the street and around the corner of our property.

Care had to be taken to purchase enough boulders of sufficient size not to be moved by the running water. To ensure the boulders would not move once in place, we used two, two-foot sections of rebar behind the large rocks to anchor each of them and help resist the pressure of the oncoming flow. We also planned to fill in behind the boulders with a buffer of small stones. The dry riverbed itself would be a large funnel-shaped area of rip rap on the other side of the boulders. Rip rap are large rocks between three and eight inches in width. We determined we would need six tons of rip rap to complete the funnel-shaped structure. We also purchased a few extra boulders to use as highlights in the dry riverbed and also to serve as an additional buffer to slow down the water as it came through. After all, we are encouraging the water to flow that way.

We designed the project so that the additional boulders would be placed in an offset, broken line formation to split and slow the water’s route. A couple of boulders further down would offer more resistance as the water picked up speed.

Read Control Flooding in the Desert – Part II

Delivery of Boulders

Riverbed at Project’s Start

Rough Boulder Placement in Riverbed

Mary with Rip Rap Remains After a Previous Project

Read Part II – Control Flooding in the Desert

Read Part III – Control Flooding int he Desert

Gardening on the Moon, www.gardeningonthemoon.com, originally published this post