Monday, October 1, 2007

October BMP Q&A

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

Q:   In June and July you described several key attributes or criteria to help to identify ephemeral and intermittent streams. Can you provide similar identifiable attributes or criteria for perennial streams?

A:   Certainly, it is important to remember that there are three general classifications of streams that are used to describe streams: perennial, intermittent, and ephemeral. Both perennial and intermittent streams should have a SMZ according to the Texas forestry BMP guidelines. Ephemeral streams do not necessarily need a SMZ but in some cases it is wise to leave some trees to buffer the stream especially if it is clear that the stream may erode or “wash” if nothing is left. This article will look specifically at perennial streams. If you need more information about classifying intermittent or ephemeral streams you can look back at the June and July editions of the Texas Logger or you can find the information in the Texas Forestry Best Management Practices manual or “the bluebook.” defines, the term “perennial” as an adjective: “lasting for an indefinitely long time;enduring” and also, “lasting or continuing throughout the entire year, as a stream.” Perennial streams have regular flow usually 90% to 100% of the year (10 ½ months to 12 months) under normal climatic conditions. During times of drought, some perennial streams may cease flow but this is not the “normal” condition of these streams.

While this definition seems at first glance to limit the number of streams that fall into this category, there are still a lot of streams in Texas that fit this definition. There are a lot of spring fed streams that a person could easily step across that fit this description. A spring that flows 10 ½ months or more is a perennial stream.

During the drought conditions and summer months, identifying flow characteristics can often be difficult. If flow cannot be determined, the presence of five or more of the following characteristics should be helpful in recognizing a perennial stream:
  1. Well-defined channel.
  2. Water pools present, even during dry conditions.
  3. A channel that is almost always sinuous (winding or curvy).
  4. Evidence of fluctuating high water marks (flood prone width) and/or sediment transport, also the indication of a flood zone parallel to the stream by sediment deposits, sediment stained leaves, bare ground and/or drift lines.
  5. Evidence of soil and debris movement (scouring) in the stream channel. Leaf litter is usually transient or temporary in the flow channel.
  6. Wetland or hydrophytic vegetation is usually associated with the stream channel or flow area. Also, even along deeply incised or “down cut” channels there is usually wetland-like vegetation present along the banks.
  7. Predominately gray soils (except soils of deep sands) with a loamy to clay texture. Red mottles or “specks” are usually present in gray soil matrix.
  8. Usually identified on USGS topographic maps as a thin blue line or identified on a NRCS soil maps as a black line separated by one dot.
  9. Perennial streams are considered “Waters of the United States” and therefore fall under the jurisdictional limits of the authority of the U.S. Army Corps of Engineers under the Clean Water Act.
These characteristics are found on page 60 of the Texas Forestry Best Management Practices book or “bluebook” and are designed to be a guide to help determine stream classification.

While it is important to know the differences in the streams and how to identify them, it is equally important to know that intermittent and perennial streams are treated in the same manner in the “bluebook.” The guidelines and recommendations should be applied the same once a stream is determined to be at least an intermittent. As you conduct your operations, always remember that your actions in the woods have the potential to affect water quality either positively or negatively.

For more information regarding BMPs consult the Texas Forestry Best Management Practices book, contact your local Texas Forest office, or you can contact me.

* This article was published in the October 2007 issue of the Texas Logger

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