Q: I own a tract of timber that has several streams running through it and I am planning on cutting the tract in the near future. Although I have heard of Streamside Management Zones (SMZs) I know very little about them. Do all streams need these SMZs and if not how do you tell which streams do?
A: This is a very good question. To start with not all streams need an SMZ left along the stream bank. Streams are divided into three groups (perennial, intermittent, or ephemeral) based on the amount of time during the year that water flows through it. The Texas Forest Service recommends that a 50-foot SMZ be left along side perennial and intermittent streams. Professional judgment should be used on ephemeral streams or drains. Sometimes it can be hard to distinguish one type of stream from the other, especially in transition zones where one type of stream is turning into another type. To help you in determining stream type, I have listed some common characteristics for each stream type below.
A perennial stream will flow at least 90% of the year and have a well-defined channel. This channel will be winding or sinuous and show evidence of soil and debris movement. Water pools will be present, even during dry conditions. High water marks are sometimes noticed along the stream, as well as wetland vegetation, such as mosses, ferns, and some woody species. Gray soils with red specks are associated with these types of streams. Remember that the Texas Forest Service recommends leaving a minimum width of 50 feet on either side of perennial streams.
An intermittent stream will flow at least 30% of the year and this is usually during the winter months. Intermittent streams also have a well-defined channel that is winding or sinuous. The channel will also show evidence of soil and debris movement from one part of the stream to another. Water pools are only present during wet conditions and high water marks along with wetland vegetation will occur in these areas. Intermittent streams usually have brown soils with gray soils mixed in. Again the Texas Forest Service recommends leaving a minimum width of 50 feet on either side of intermittent streams.
An ephemeral stream or drain only flows during or shortly after rain events. These streams do not always have well-defined channels because they are short lived. Ephemeral streams are generally always straight, lack water pools, and high water marks and wetland vegetation are not found. The soils in this area are usually characteristic of the surrounding lands. The Texas Forest Service recommends that professional judgment be used in determining whether or not an SMZ should be left along ephemeral streams. Some may choose to leave a small SMZ or stringer along an ephemeral stream while others may choose not to leave one.
SMZs are very important in protecting our streams from increased temperatures, excessive erosion, and provides habitat for various species of wildlife. SMZs can be thinned in order to remove some of the economic value, however it is important to leave a minimum of 50 square feet of basal area, evenly distributed. Senate Bill 977 can help reduce the financial burden of leaving an SMZ. If any debris from the thinning of an SMZ should end up in the stream, it should be removed immediately to prevent the stream flow from becoming blocked.
The recommendations for SMZs as well as other BMPs can be found in the Bluebook. If you need a copy of the Bluebook you can get one from your local Texas Forest Service office or you can view it online at http://txforestservice.tamu.edu/water. If you have any questions or comments about BMPs please feel free to call me at (936) 639-8180.
* This article was published in the June 2004 issue of the Texas Logger