Objective Identification of Pools and Riffles

Abstract

This paper presents a new technique for objectively identifying pools and riffles. The technique is termed the bed form differencing technique and as its data base has bed elevations surveyed at a fixed interval along the channel. These elevations are differenced, and the difference or elevation change values are used to identify pools and riffles. Where the cumulative elevation change since the last bed form exceeds a certain tolerance value, a new bed form is considered to exist, the type of bed form being determined by the direction of the elevation change. Analysis of a small stream in western New York suggests that the most realistic pool‐riffle sequence is obtained where the tolerance value is 0.75 times the standard deviation of the difference values. The bed form differencing technique can be used to identify bed forms other than pools and riffles, such as ripples and dunes, by simply modifying the surveying interval to reflect the scale of the bed forms.