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.

Wealth of Information at Your Fingertips!

Forest landowners who want some information on various aspects of timberland ownership can go to the Texas Forest Service website.  For a concise collection of links to all kinds of information, go to the Water Resources web page - http://texasforestservice.tamu.edu/water -  and click on "Publications."  Scroll down until you find Forest Landowner Briefings.  The first edition covers a wide variety of topics pertinent to forest landowners.  Links are included so the viewer can delve more deeply into each topic.  The second edition, which was just published (August 2012), looks a little farther into more specific topics, including wildfire recovery, wildlife management, endangered species, forest taxes, and non-traditional income on forestlands.

These two newsletters were originally intended to be a resource for landowners with forested property in East Texas but living out of state.  However, any forest landowner can benefit from the information provided, especially new landowners who aren't sure where to start and what is available to them.  Take a look!

Photo by Ronald F. Billings, Texas Forest Service

Crushed Concrete on the Jones State Forest

While more expensive than seeding, armoring a road surface with rock is an excellent way to prevent erosion and improve access, especially on roads that remain wet for long periods of time, experience heavy traffic, or are prone to erosion.  A popular rock to use is crushed concrete.  When structures such as roads and buildings that are made of concrete are demolished, it has become common practice to take this concrete and crush it for reuse.  After the concrete has been crushed, magnets remove any steel such as rebar that may be present.  The final product is a hard, granular aggregate that is composed of sand, gravel, and crushed stone. 

Crushed concrete is often cheaper than using natural rock aggregate since it is a byproduct of demolition.  Crushed concrete stabilizes relatively quickly once it is applied to the road creating a firm road surface.  Just as with using other rock material for roads, crushed concrete drains faster than if the road was left with its natural dirt surface, reducing the potential for rutting in the road. 

This week, 118 tons of crushed concrete was spread out on a section of road in the Jones State Forest in Conroe, Texas by TFS Resource Specialists Mike Adams and Ray Uballe.  The section of road where the crushed concrete was distributed is just one stop on the best management practices (BMP) tour down on the Jones.  The tour consists of various BMPs that have been put into application so visitors can not only learn about these BMPs, they can also see them in use. 



 Resource Specialist Ray Uballe spreads the crushed concrete following the delivery of the material

 


Resource Specialist Mike Adams smoothes the newly applied crushed concrete

  







 

  







 



August 2012 BMP Q&A

By: Todd Thomas, BMP Forester, Texas Forest Service

Q: While discussing streamside management zones (SMZs) with a co-worker, the topic of thinning came up.  I told him that the guidelines recommend leaving at least 50 ft² of basal area per acre.   He insisted that it was 50% crown cover.  Who is right?   Is there really a difference?

 A: Great question.  SMZs provide many critical functions in protecting water quality, so it is important that we don’t limit their effectiveness through over harvesting.  Not only do these areas slow and filter runoff, they also provide shade to streams, maintain bank stability, and lessen the impacts from raindrops that can lead to erosion. 

Now back to your question.  In essence, there is some truth to both answers, though in the event you have a friendly wager riding on this, I would have to side with you.  According to the Texas Forestry Best Management Practices Handbook, within the SMZ of perennial and intermittent streams, a minimum of 50 square feet of basal area per acre should be left.  The residual basal area should be evenly distributed throughout the SMZ in order to provide adequate protection to the stream. 

So what exactly is basal area?  This forestry term is primarily used as a measure of density and is defined as the cross sectional area of a tree stem in square feet at breast height (4.5 feet above the ground).  Since this can sometimes be a difficult concept for people to understand, especially those unfamiliar with forest measurements, the BMP handbook also includes a general rule of thumb that can be used.  Retaining 50% overstory crown cover within the SMZ can usually serve the same purpose, though in order to achieve this, you probably will have to leave a little more than half the trees in a forest that has reached canopy closure. 

Basal area, once you understand it, is very easy to measure, especially when you have the right tool.  A BAF 10 factor prism can quickly help you determine the residual density of the SMZ.  If you don’t have a prism, the BMP handbook includes a section on page 107 that provides information on how to calculate basal area. 

Remember, any time you are working in SMZs, special care is necessary in order to maintain their critical function.  While it is important to manage these areas, operators should continue to follow all related BMPs.  Roads and skid trails should be located outside of these areas when feasible and logging decks should be at least 50 feet from the edge of the SMZ.  Directional felling should also be used to minimize the amount of debris that enters the stream.  Logging slash that inadvertently enters the stream should be removed.  Lastly, minimize the number of bank trees that are harvested, as these help protect the integrity of the stream, provide shade, and stabilize the bank. 

Thanks for taking the time to increase your knowledge of BMPs and keep up the good work out there in the woods.  Also, please send in any BMP questions you may have, because chances are if you are unsure of something, there is someone else out there who has the same question.  Feel free to contact me at tthomas@tfs.tamu.edu or (936)-639-8180. 

*This article was published in the August 2012 issue of the Texas Logger