Texas Forestry BMPs - Constructing Waterbars and Wing Ditches

Texas Forestry BMPs - Locating Waterbars

Outfall Protection

What exactly is outfall protection?  Outfall protection is an essential element of proper culvert installation and can certainly extend the life of your culvert.  Outfall protection most often consists of rip rap or other large aggregate placed at the end of the culvert to intercept and absorb the energy produced by the water exiting the culvert. 

Rock Outfall Protection

As water flows down a ditch or stream, it is gaining speed or velocity.  This velocity increases once the flow of water is concentrated in a culvert.   Culverts also tend to have more smooth edges, or less roughness than the ditch or streambed to slow this water down.  Once this water exits the culvert, it is moving relatively fast with lots of power ready to move some soil and cause erosion.  In addition to scouring out the channel down from the culvert, this water tends to swirl around as it leaves the culvert and can eventually wash out the culvert, costing you money to come in and re-install your culvert. 

Outfall protection intercepts this flow and spreads it out, thus reducing the speed of the water and its erosive power.  Outfall protection can be as simple as some old bricks, busted up concrete, old tires, or large rock.  On cross-drain culverts, where you are transferring runoff from across the road, you may want to not only put outfall protection under the end of the culvert, but also on the bank adjacent to the culvert exit, to help preserve the bank and prevent excessive erosion.   On culverts used for creek crossings it is often important to not only have outfall protection on the culvert exit, but also on the sides of the banks on either side of the culvert exit.  This will prevent swirling water exiting the culvert from eroding the stream banks and eventually blowing out the sides of your culvert. 

Outfall protection can also be an important component of wing ditches on some of your woods roads that are generally only used during forest operations.  In these instances, you may not need to invest in large, rock aggregate, but instead can prevent excessive erosion by placing slash or brush at the outlet of the wing ditch.  Another method of providing outfall protection on wing ditches could be using vegetation.  If this is an area that doesn't receive a large amount of runoff, it is a good idea to use our seeding chart on page 67 of the blue book. 

In conclusion, outfall protection is essential in protecting your culvert, ditch, stream, wallet, and water quality in general.  Outfall protection will save you money by not having to re-install culverts and reduce the frequency that you have to come and pull your ditches.  Outfall protection protects streams health and preserves water quality by reducing the amount of sediment traveling downstream that result from stream bed and stream bank scour.  

The basics of waterbars and wing ditches

The primary pollutant that enters our waterways from forestry operations is sediment.  This sediment comes mostly from roads, skid trails, and firebreaks.  Sediment is carried from overland flow that has gained enough velocity to detach soil particles and carry them with it; this overland flow, if not slowed down and dispersed, ends up in the stream, sediment and all.  One method of slowing down overland flow, as well as dispersing any sediment that it is carrying with it is to construct waterbars in trails, roads, and firebreaks.

Waterbars should be constructed at a 30-45 degree angle, turning overland flow out and away from the road.  

Accompanying a waterbar should be some sort of a turnout, more commonly referred to as a "wing ditch."  As the overland flow is intercepted by the waterbar, it is diverted into the wing ditch and dispersed before it has the opportunity to gain speed and cause further erosion.  It is also important to note that wing ditches should be constructed to be more flat than v-shaped.  This encourages diverted flow to dissipate rather than be concentrated.  

When constructing waterbars it is important to be sure that both ends are tied in to the edge of the road.  This prevents "blow outs" or water from going around the waterbar.  

Waterbars should never be constructed perpendicular to the road, this forms a dam, causing water to stand in the road.  Even though any overland flow has been put to a stop, the integrity of the road has been compromised, due to the 90 degree waterbar with no turnout accompanying it.  

Waterbars and wing ditches should never discharge into streams.  This increases stream bank erosion as well as increases the amount of sediment that enters the stream as a result of operations.

August BMP Q&A

By: Chuck Coup, BMP Forester (Ret.), Texas Forest Service

Q:  There are all sorts of difficult situations that can arise when my guys are attempting to construct a functioning wing ditch. Sometimes they work and sometimes they don’t. Can you tell me some of the most common problems you come across with wing ditches?

A:  Isn’t it amazing how a structure as simple as a wing ditch can sometimes be so troublesome! The primary function of a wing ditch is to collect runoff water from the road surface and roadside ditches and disperse it into stable areas away from water bodies or other sensitive areas. They are typically most effective when used in conjunction with a waterbar that intercepts, diverts, and drains runoff water from the road surface and the roadside ditch on the opposite side. It is really nothing more than a water outlet for the road, but knowing where and how to construct them in certain situations can be very tricky!

One of the most common problems I see with wing ditches is that they are longer than necessary. It is generally not effective to construct a wing ditch that carries runoff water long distances away from the road. This practice unnecessarily exposes additional soil to erosion and increases the distance that the runoff water has to flow before reaching stable, vegetated ground cover. Long wing ditches also run the risk of discharging polluted water into or near water bodies or other sensitive areas. Keep your wing ditches only as long as necessary to encourage the water to flow away from the road. One exception to this may be in extremely flat areas where it is difficult to get the water to drain away from the road. Typically though, if you have a little topography, gravity will do the trick. If you think you need to construct a long wing ditch in order to deal with a large volume of water being carried down your road, you should instead consider increasing the frequency of your wing ditches (and waterbars) by putting them closer together. That will divide the amount of water you are trying to manage between wing ditches.

Another problem I often come across is wing ditches that are constructed as narrow channels using the corner of the skidder or dozer blade. I frequently see these V-shaped channels in combination with wing ditches that are too long, resulting in a turnout that erodes and carries sediments excessive distances – completely the opposite of what we want. A better approach is to keep the dozer or skidder blade level with the ground and make a wide flat outlet that disperses the water over a broad area. This kind of outlet promotes sheet flow versus channel flow which spreads the water out and reduces its speed. Slow moving water cannot carry sediments as efficiently as fast moving channelized water can.

Other problems are typically related to where the wing ditch discharges. I occasionally come across waterbars that are correctly constructed on the edge of an SMZ but have a wing ditch that carries the polluted water through the SMZ and discharges it either directly into or within feet of the stream channel. That’s bad news for the fish and other aquatic wildlife. Another situation I repeatedly see are wing ditches constructed down steep slopes which eventually leads to excessive erosion. One way that you might avoid these situations is by putting a gentle uphill turn in your wing ditch outlet. “J-hooking” your wing ditches, as it is called, can help to divert the water away from sensitive areas like stream channels or steep slopes and also helps to slow the water’s speed. However, don’t confuse this practice with the futile attempt to carry water uphill by putting wing ditches on the high side of the road or against the slope of the land. The wing ditch should still have a slight down grade and follow the natural contour of the site (and be flat and only as long as necessary). That’s one approach that I have found to be effective, but I am sure that you guys have come up with more creative solutions to these problems. If you have, drop me a line as I would love to hear them!

Finally, if you get a chance, I would recommend that you go back and take a look at some of the wing ditches you installed in the past, especially the ones that you were uncertain about. See if they worked and if they didn’t what you might need to do differently in the future.

For more information on wing ditches and other BMPs visit the Texas Forest Service webpage at http://txforestservice.tamu.edu/water or contact me by phone at (936) 639-8180. 

* This article was published in the August 2011 issue of the Texas Logger

September BMP Q&A

By: Jake Donellan, BMP Forester (Ret.), Texas Forest Service 

Q: I have a question about wing ditches. My guys put them in whenever they think one is needed. I was wondering do you have any specific guidelines as to how many and how often they need to install them?

A: Wing Ditches are water turnouts that divert water away from the road and/or a side ditch. The purpose of a wing ditch is to collect and direct water from road surface runoff into an undisturbed area. It is necessary that the wing ditch allow the water to slow down and to channel the water away from the road and roadside ditches. There are some guidelines to use on when to install wing ditches and how often. Experience, which should never be downplayed, also plays a large role in knowing when and where to put the wing ditches along your roads.

You probably want to use wing ditches anywhere where there is an accumulation of water or a section of road or trail. The water should be diverted so as to decrease the volume and velocity of the water especially on slopes. You also should use wing ditches where there is a buildup of drainage water in roadside ditches. This buildup can eat away at roadbeds and scour out the roadside ditch itself. The recommended guidelines for wing ditches are on pages37 and 38 in the Texas Forestry Best Management Practices Manuel sometimes called, “the Bluebook.”

The spacing of your wing ditches depends on slope and soil conditions. On 2%-5% slopes the spacing should be no greater than 200 feet apart. On slopes 5%-10%, the distance between wing ditches should be no greater than 100 feet apart. Slopes greater than 10% should have wing ditches no more than 75 feet apart. Your experience should tell you that you might need more wing ditches if you are working on highly erodible soils. One other thing to keep in mind is that wing ditches should not feed directly into streams, gullies, or adjacent drains or ditches.


Wing ditches should be installed so that they leave the road ditch line at about a 30 to 45 degree angle to the roadbed and be designed to follow the natural shape (contour) of the land. The runoff water can be spread out, filtered by brush, or retained in the wing ditch. Wing ditches are very effective tools to help maintain roads and trails. Wing ditches can be even more effective when used in conjunction with other road BMPs like water bars, rolling dips and crowning the road. I hope that answered your question. Does anybody else have any other suggestions or methods that they use?

If you are in the area stop by see me. If you have a BMP question you would like answered, please contact me.

* This article was published in the September 2000 issue of the Texas Logger