Pool-riffle sediment and flow dynamics have been studied for many years, but there has been relatively little investigation on how field observations might be influenced by the variability of pool-riffle morphologies. In this letter we present a database of quantitative and qualitative measurements from sites where pool-riffle morphologies have been studied and apply two morphologic classifications that compare a) discharge and slope, and b) specific stream power and a representative coarse bed particle size. The classifications show that pool-riffles appear in different positions relative to mobility and morphologic transitions, which indicates that they occur within different flow and sediment regimes. Patterns in the distribution of studied pool-riffles show useful trends as well as an important diversity, the appreciation of which may help to clarify the importance of different flow and sediment transport phenomenon that underlie pool-riffle mechanics.