Ditch to Dry Stream Bed
So you have an ugly ditch in your yard that you just know could look so much better. Perhaps you have seen a dry creek bed in someone else’s landscape. Or maybe you saw a stream bed in a book you liked. Well, it’s really fairly easy to do, so let’s talk about how you might go about it.
Asses Your Dry Stream Bed
First off, “easy” is a relative thing when it comes to building a dry stream bed. When I say easy, I mean that you don’t need any special skills and depending on the scale and length of the ditch (or swale), hopefully you don’t need any special equipment. However, you will need a strong back and some extra money. The first thing to do is to assess the job and determine if it is suitable for you to do yourself, with friends and family (very good friends) or if you will need to hire a contractor. Think about the level of effort required versus your own physical abilities and stamina. Don’t forget to factor in the heat, weather, your schedule and your availability. This is a manual labor job; it requires digging, hauling materials and placing stones from small to large. You also need to have a good sense for aesthetics to place stone and plants. Ok, so now that you thought through all that, hold your thought. Let’s clarify the work and process before you make up your mind to go and build a dry stream bed all by yourself.
Now let’s assess the existing situation. You need to know how your ditch functions before you do anything. Is the ditch a real creek with water in it all the time? If so, stop right now, there are many different laws and regulations that protect perennial streams and creek beds. In some municipalities even dry washes are protected and any disturbance requires permits. Also if your ditch or swale (a swale is a shallow gently sloping ditch) is part of a system that drains a larger area where water enters the ditch from outside your own yard, then altering its characteristics to make a “dry stream bed” look may fall under specific laws and regulations in your area. It is always best to consult your local jurisdictional agency before starting any dry stream bed conversion. Also if your home lies in a subdivision with covenants, be sure to check with the design review board or management. The good news is that in most cases, the improvements you will make are generally considered beneficial to the health of the drainage way and downstream water quality.
Grading a Swale for a Dry Creek Bed
Ok, so you have determined that local regulations allow your ditch or swale to be converted into a dry stream bed, what’s next? How deep and degraded is your ditch? If the ditch is several feet or meters deep with eroding sides and is often filled with rapidly moving water, then conversion to an attractive stream bed may be problematic. Fast moving water can easily move even larger boulders. I have personally seen water move boulders the size of refrigerators many feet in one major rain event and wash tons of soil away at the same time. Also, if the ditch is very deep, then anything you place in the bottom will be invisible unless the viewer is standing right at the edge. You may have to reshape your ditch and make it into a “swale”. Depending on the depth this may require significant grading using mechanical equipment such as a skid steer loader (bobcat, loader, backhoe, etc) or bull dozer. These activities often require permits and special approved plans done by licensed professional landscape architects or civil engineers. However, for now let’s assume your ditch is shallow or small so you can do it yourself. Ideally, you want to use a shovel, dirt rake, and small equipment to create a shallow swale that is formed with gentle slopes not steeper than 5:1 (that’s five feet in distance for every 1 foot in fall). For example, a swale ten feet (3 meters) wide will only be about one foot (0.3 meters) deep. There is nothing special about making a swale; it just takes good old fashioned manual labor, that is, unless you have access to a small skid steer loader (bobcat). Note: You can rent these a tool rental stores and learn to drive them in a few minutes.
Before we leave the grading section of this “how to” article, let’s discuss the slope and flow direction of your dry creek bed. In general, it’s never a good idea to allow the water to flow straight down the slope because it speeds up erosion and can be detrimental to your design. Fast moving water will wash away smaller stones and even plants. If possible, consider adding some gentle curves into the swale design. Angles should not be extreme to avoid water washing over the banks in the turns. Turns should be gentle at approximately 10-30 degree angles and transitions should be uniform. The final design will look best if there are several gentle curves along your swale. Note: If your swale (ditch) is short, say less than thirty feet, adding more than one or two curves may not look good. In shorter swales, simply modifying the width of the stream bed can create the same effect. Also, as with any natural stream, the stream bed edges are never straight and clean, the widths vary where fast moving water breaches the banks and fallen logs and large boulders create deep pools or eddies. You can mimic these features in the landscape by widening the stream or creek bed and digging out deeper areas along its path.
After you have graded and curved your swale it’s time to set up the infrastructure. The amount of infrastructure you need for an effective low maintenance dry stream bed is determined by the amount of water and erosion you expect. If the ditch will experience significant (six inches or more of fast moving water) amounts of water on a regular basis you may need to line your stream bed completely with larger fractal (broken with lots of straight sharp edges) stones, often referred to as “rip-rap”. These stone will lock together and form a strong armor to the stream bed. On the other hand if the amount of water in the swale is expected to be limited you may want to put down a weed barrier (geo-textile) before putting down any stones. This will keep the weeds down and make your life easier. Note: Do not put down solid plastic sheeting, plastic sheeting stops the water from percolating into the soil under the creek and is bad for the health of the soil and plants that have roots in the area. Also do not put weed barriers under stones where lots of fast moving water is expected.
Let’s talk about STONES for your dry stream bed
Now it’s time to talk about the stone for your dry stream bed. Personally, I like to use local stone or what some call the “vernacular” stone of the area. By using local stone, the creek bed will have a more natural look. However, in some cases local stone may not be available or desirable, so feel free to use the stone of your choosing. In real creeks stones in the stream bed are typically very well worn and eroded. They are almost always smooth. I like to use what the contractors commonly refer to as “river slicks” or “river stones”. In some cases these are real stones from river beds. Note: Some people are very concerned about where these rocks are obtained. Be sure your supplier is using weathered fieldstones or glacial deposits and not using stones obtained from local streams and rivers. Once you have found a stone material that you like, be sure it is available in the quantity and size range you require for your project. You will need small stones to cover about 60% of the surface. Small stones should be from two to five inches or from egg sized to fist. Then you will need about 30% cover in medium stones from six to twelve inches in size. Think grapefruit to watermelon and relatively easy to lift and move. Finally you will want a few large boulders along the edges and sparingly in the creek bed. Approximately 10% of the creek bed should be covered in larger boulders. If it is a do-it-yourself project then large is the largest size you are capable of moving by yourself. Think pillow size boulders. Note: You can move some really big boulders using a pry-bar and wedging them into place. Also using burlap or geotextile fabric (like a piece of silt fencing) you can wrap short pieces of wood into each of the four corners and cradle large boulders. Using this method, two or more men or women can move very large boulders by dragging them. The largest boulders can be moved by mechanical equipment. The size of the boulders and all stone should generally be determined by the scale of the dry creek bed and the velocity and volume of water. The greater the amount of water and velocity and grander the project, the larger the stones should be. A small back yard stream bed with little outside influence should not have any boulders bigger than two men could move without equipment. On the other hand, a swale twenty feet wide and several hundred feet long in front of a business park could easily have boulders the size of a lounge chair.
Stones meeting these requirements can generally be found at your local “earth product” or stone supplier. If you live in a larger city, these places should be easy to find. If you live in a rural area you may have to order stone delivered from a local metropolitan area or you may have to locate your own source locally. Be careful to obey the law and obtain permission when obtaining your own stones. I often find people giving away field boulders on “craig’s list” or site developers in the area needing to get rid of truck loads. When purchasing stone, these smaller slick or weathered stones are generally sold by the ton and packaged in “cribs” or wire baskets on wood pallets. Prices vary across the globe depending on availability, demand, and location. In general at this time in the USA, average for a ton of river slicks is between $100-200 ton (2010 price). Coverage for stone depends greatly on size. Consult with your supplier for the best answer, in general though 1 ton of smaller gravel will cover about 100 square feet. Coverage for larger stones can be a lot less. Note: Large boulders are typically sold individually or in groups of several stones on one pallet. They are usually sold by the ton. Note: A semi-truck (18 wheeler) will hold approx. sixteen (16) pallets. A tandem axle dump truck will usually hold roughly 15-16 tons.
Finally, it’s time for the finishing touches. The finish of your dry stream bed is the most important part. Success depends on the details. It’s easy to place large boulders in a line along the edges of the channel but in reality that’s not how real creeks work or look. Take a drive and see a few for yourself. Only deep fast moving water can move larger boulders, so that is often where you find larger boulders, randomly placed in the middle area with only a few scattered along the edges. Also, you find smaller fine materials spread in sand bars and washes that vary from side to side. There may also be plants that creep into the edges. Fast moving water keeps plants from growing, especially larger rigidly branched shrubs. These larger plants are generally only found at the edge and behind (downstream) larger boulders. Smaller flexible plants that can handle periodic inundation may be found nearer the main flow of the water. I like to use iris varieties for this purpose. Also boulders are rarely sitting on the surface. They are usually partially buried. You may only see the top 2/3rds or ½ of the larger boulders.
When I am placing my rocks I first set out my weed matt. Then I place my large boulders so I have plenty of space to move and room for helpers. Note: It is really hard to walk on rocks when placing large boulders and you cannot drag large boulders over smaller ones without messing everything up. After the large boulders I place the medium boulders. I place things randomly being sure it looks natural. Clusters of rocks together make the stream bed look natural. Sometimes I randomly toss boulders to let them fall naturally. Finally, I place the smaller rock and gravel. Using a wheelbarrow (wheel barrel) I dump rocks to cover all the spaces in-between. I cover the entire area with no spaces except for where I intend to plant shrubs or perennials.
Planting your creek bed
For plants I use a number of water tolerant plants, unless the creek is truly an aesthetic with no chance for regular water, in which case I plant xeri-scape drought tolerant plants like native grasses, etc. In my area (Southeast USA) I plant some of the following as the most common; miscanthus spp., iris spp., red and yellow twig dogwood, swamp hibiscus, tag alder, creeping jenny, hydrangea, lizard tail, arrow head, pickerel weed, carex spp., acous ogon, clumping liriope, mondo grass, evergreen ferns, etc. Note if your stream bed is in shade or sun you will need to select the appropriate plants.
Summarizing the work
In summary, this is not really an easy job despite what I said in the beginning. Building a dry stream bed that looks good takes lots of muscle, time, design skill and money. Unless your swale or ditch is very small, I would recommend hiring a contractor for this job. However, if you choose to build your own dry stream bed, the fruits of your labor may be very rewarding indeed. The cost of a dry stream bed can vary from two to three dollars a square foot to more than double that. Stone alone will cost you at least $1.50/sf delivered. I hope you all find this article very informative. Please post your questions below.