Discrimination between mountain stream channel types using independent control variables

We use a large and diverse dataset from mountain streams around the world to explore our ability to classify reach-scale channel morphology using easily measurable control variables. The dataset includes 136 step-pool reaches, 44 plane-bed reaches, and 93 pool-riffle reaches from streams in the western United States, Panama, and New Zealand. We used stepwise discriminant analysis to select the most parsimonious subset of variables for classifying channel type. A 3-variable discriminant function using slope, D84, and channel width produced a classification error rate of 24% (103 reaches correctly classified). Seventy percent of plane-bed reaches were correctly classified (16% incorrectly classified as pool-riffle, 14% incorrectly classified as step-pool). Sixty-seven percent of pool-riffle channels were correctly classified (31% incorrectly classified as plane-bed, 2% as step-pool). Eighty-nine percent of step-pool reaches were correctly classified (9% incorrectly classified as plane-bed, 2% as pool-riffle). The partial R2-values indicate that slope is by far the most significant single explanatory variable. The ability to accurately classify channel type in other regions using the elegant 3-variable discriminant function developed from the entire dataset has important implications for water-resources management and for understanding relationships between process and form in mountain streams.