Elevation: a consistent and physically-based framework for classifying streams

Abstract

ABSTRACTWe present “elevation above mean sea level” as a unifying parameter for stream classification purposes and identify consistent morphological trends exhibited by several stream properties with changing elevation. Published geometric data of 873 stable channel reaches from varied physiographic regions, representing a wide range of climatic, hydrologic and geologic conditions, were originally segregated into 13 elevation bins. For each bin, the individual highest probability values of three non-dimensional variables (width-to-depth ratio, channel gradient, and sinuosity) were calculated. Based on similar mode values, several sequential elevation bins were merged to generate five distinct elevation zones (0–75, 75–450, 450–1050, 1050–1500 and 1500 m and above). Moving from lower to higher elevation zones, width-to-depth ratio initially increased and then suddenly decreased above 1500 m, whereas channel gradient consistently showed a rising trend. Sinuosity exhibited high values only at 0–75 m. For all other zones, it was lower, demonstrating no trend and remaining approximately constant. The above tendencies persisted even when this elevation-based analysis was performed separately on cobble, gravel and sand streams.