February 2013, BMP Q&A

By: Todd Thomas, Water Resources Forester, Texas A&M Forest Service

Q: In the quiz last month you asked a question where we would need to know the slope in order to have appropriately spaced windrows.  My question is how are we supposed to know the slope in the field off hand without a tool such as a clinometer? 

A: I am glad you asked this question and I am always glad to highlight areas of the blue book.  However this time I will not be referencing the text of the book, but a feature that many of you may have noticed, but never paid much attention to.  This feature is the slope calculator. 

The slope calculator can be found on the inside of the back cover of the blue book.  There are instructions on how to use it, but since you asked, I will go ahead and explain.  In addition to your blue book, you will need a piece of string, approximately 12-inches long and something to use as a weight, such as a small nut or washer.  First, tie one end of the string to the middle ring of the spiral binding or punch a hole through the cover of the book at the apex of the slope calculator.  Go ahead, it is okay.  There is a small circle there for your reference.  Next, tie your small weight to the loose end of the string. 

Now that your slope calculator has been constructed, here is how you will use it.  The spiral binding should be on top, use this as your sight.  With the binding parallel to the ground, sight the book up or down the slope (depending on which way you are facing), the string will hang vertically and the slope can be read directly along the line where the string lies.  The number on the line with the string is your percent slope.

Now that you are aware of the slope calculator, there are no excuses for not having your blue book with you.  Not only is the book full of BMP information, it is also a tool that you can use in your day to day functions.  In addition to windrow spacing, this tool can be used for determining road gradients so you know where to locate your water control structures such as waterbars, wing ditches, culverts, and dips; in conjunction with the culvert size chart to determine culvert sizing; as well as how wide to make SMZs when near steep slopes, or any other time you need to know the percent slope in a pinch. 

In conclusion, keep those blue books handy, you never know when one might come into use.  If you need a blue book you can get one from your nearest TFS office.  Please keep your questions coming.  You can email them to me at tthomas@tfs.tamu.edu or phone them in by calling (936)639-8180.  

*This article was published in the February 2013 issue of the Texas Logger