Sunday, April 1, 2007

April BMP Q&A

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

Q:   Back in September of 2006, the BMP Quiz question dealt with how far a landing should be constructed outside of a streamside management zone (SMZ). I answered that as long as the landing was 50 feet from the stream channel that it would be okay. Evidently that was the wrong answer, could you please tell me what the distance is and what reasons there are for having if further away?

A:   This is an excellent question! The correct answer to the Quiz in the September issue of the Texas Logger should have been that landings be established at least 50 feet from the edge of the SMZ. This would thereby equate to a distance of 100 feet from the stream channel for a landing if you use the minimal 50 feet wide SMZ.

It is important to note that the “Recommended Specifications” in the bluebook call for the distance to be measured from the edge of the SMZ and not the stream channel. Rather than trying to figure out how wide your SMZ extends from the stream channel and then add the 50 feet, it is much easier to find the edge of the SMZ and establish the landing 50 feet from it.

There are a couple of reasons for this specification on landing design: The first reason is that landings almost always contain a large amount of woody debris and occasionally are the site of hydraulic fluid leaks/spills from various sources like equipment repair or unexpected hose failures etc. It is important to keep this material from entering a water source since it is deemed nonpoint source pollution. By establishing the landing 50 feet from the edge of the SMZ you create less opportunity for that woody debris and perhaps even the oil spills to reach the stream. This additional 50 feet helps in most cases to ensure that most of the excess woody debris at a landing will remain at the landing site and not end up in the stream channel if the stream floods up to and out of the SMZ, except of course under extreme flooding conditions.

Secondly the SMZ has always been referred appropriately as the “final filter” because it is the final opportunity on the site to filter overland flow before it reaches the stream. If it were necessary to establish a wider than the minimal 50 feet SMZ, say for instance on a steep sandy site, it would be counter productive to establish a wider SMZ if you created a landing 50 feet from the stream channel. This would place a landing within your SMZ thus reducing its overall filtering capacity.

Landings are high traffic areas that have the potential to concentrate some of the nonpoint source pollution that forestry operations generate. This is why it is important to keep them at least 50 feet from the SMZ or “final filter.” As always, though, each site is unique and some situations may not allow this 50 feet, when those occur it is important to use your professional judgment when placing the location of the landing in relation to the SMZ. That is the beauty of the voluntary, non-regulatory system we have in place; it allows us to set minimum guidelines but also apply common sense when the situation arises.

For more information regarding landings, streamside management zones, and BMPs consult the bluebook (Texas Forestry Best Management Practices). If you prefer, you can contact me

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