Effects of a Flash Flood on Physical Stream Characteristics and Nitrate Uptake in an Urban Stream

High flow conditions can influence the characteristics and behavior of streams. We performed a study comparing physical stream characteristics and how they are related to nitrate uptake on three reaches of an urban stream before and after a flash flood. We developed a detailed protocol for characterizing physical attributes along the stream reach, including pebble counts, longitudinal thalweg survey, width variability survey, cross-section surveys, hydraulic measurements, and spatial distribution of physical habitat units. Along with the physical characterization of each reach, we performed nutrient injections to estimate the amount of nitrate uptake occurring over the reach. Benthic organic matter content and whole-stream metabolism were also measured in each reach. Comprehensive data sets were collected at each of three reaches along one stream at pre- and post- flood conditions. By comparing variations in physical stream characteristics and nitrate uptake before and after flash flood conditions, we explored how sudden increases in flow can modify physical attributes of the stream that may influence the uptake of nitrate. We further investigated if particular physical characteristics of the stream reach are associated with nitrate uptake.