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ARS Home » Pacific West Area » Pullman, Washington » Northwest Sustainable Agroecosystems Research » Research » Publications at this Location » Publication #145091
Title: RAPID METHODS FOR MEASURING RANDOM ROUGHNESS

Author
item McCool, Donald
item PANNKUK, CHRIS - WASHINGTON STATE UNIV.
item MUTCH, PAUL - USDA-ARS RETIRED

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2002
Publication Date: 11/30/2002
Citation: Mccool, D.K., Pannkuk, C.D., Mutch, P.W. 2002. Rapid methods for measuring random roughness. Applied Engineering in Agriculture.

Interpretive Summary: Soil random roughness is important in controlling and predicting both wind and water erosion. A number of techniques, from simple to very sophisticated, have been proposed to measure or estimate random roughness. Here-to-fore, criteria to assist a researcher or conservationist select an appropriate technique for a specific task have been lacking. Because of the need for rapid field assessment of random roughness, photographs of a range of random roughness conditions were taken to be used as visual guides to estimate random roughness in the field. The method requires no contact with the soil and thus can be used in extremely wet or dry conditions. It is sufficiently accurate for the conservation planning prediction models currently in use. The photographs were calibrated using a 6-foot wide pin-type profile meter, and random roughness was calculated as the standard deviation of the pin heights. During the course of the analysis it became apparent that, if the roughness is truly random, the difference in elevation of the highest and lowest points along the width of the profile meter is directly related to random roughness. This was found to be a linear relationship. The method was tested with a second set of data collected with the profile meter and a 4-foot straight edge. A test of a line-shortening or chain method was also included. The three rapid field methods (photograph, elevation difference, and chain-shortening) are compared with the profile meter method. Results of the study allow a researcher or conservationist to select a method for measuring or estimating random roughness that meets their needs for speed, reliability, and accuracy.

Technical Abstract: Soil random roughness is an important variable in predicting and controlling both wind and water erosion. A number of techniques, from simple to very sophisticated, have been developed to measure or estimate random roughness. Here-to-fore, criteria to assist a researcher or conservationist select an appropriate technique for a specific task have been lacking. Because of the need for rapid field assessment of random roughness, photographs of a range of random roughness conditions were taken to be used as visual guides to estimate random roughness in the field. The method requires no contact with the soil, can be used in extremely wet or dry conditions, and is sufficiently accurate for prediction models currently in use. The photographs were calibrated using a 6-foot pin-type profile meter, and random roughness was calculated as the standard deviation of the pin heights. During the course of the analysis it became apparent that, if the roughness is truly random, the difference in elevation of the highest and lowest points along the width of the profile meter is directly related to random roughness. This was found to be a linear relationship. The method was tested with a second set of data collected with the profile meter and a 4-foot straight edge. A test of a line or chain shortening method was also included. The three rapid field methods (photograph, elevation difference, and chain shortening) are compared with the profile meter method. Results of the study allow a researcher or conservationist to select a method for measuring or estimating random roughness that meets their needs for speed, reliability, and accuracy.