Variability of acoustic properties among whitewater features

Acoustic signals produced by rapids, riffles, and waterfalls appear to depend on discharge and whitewater feature morphology, and may be used to monitor streamflow in the absence of traditional stream gauges. However, whitewater sounds are not well understood and it is not clear how the relationship between discharge and sound varies among different types of whitewater features. To address this, we analyze infrasound and audible-sound recordings from several whitewater features, including dam spillways, low-head dam spillovers, natural waterfalls, and continuous rapids. Feature discharge levels range from several liters per second to over a hundred cubic meters per second, and discharge measurements from permanent stream gauges are used for correlation when available. Preliminary results show that although some whitewater features have simple relationships between discharge and sound spectrum, others have complex, non-monotonic relationships, possibly due to discharge-dependent changes in hydraulic jump morphology. Correlation of feature morphology and sound-discharge relationships will identify characteristics of favorable monitoring sites and help bring acoustic stream gauging from a promising idea to a practical field method.