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
