Using Temperature to Infer Real-time Changes in Beach Bathymetry - Fiber Optics in the Nearshore

We present a new method for using temperature to infer bathymetric change of an artificial beach placed in the O.H. Hinsdale Wave Research Laboratory Large Wave Flume at Oregon State University. The temperature latency technique compares recorded temperature measured within the sediment with modeled temperatures expected to result from surface water temperature changes through time. Because surface-driven temperature changes are attenuated and lagged in time with deeper burial, we can estimate depth of burial by examining the time series of temperatures measured within the sediment relative to surface temperatures. Temperatures are recorded at more than 900 cross-shore locations across two depths using a fiber optic distributed temperature system (DTS) and at 2 cross-shore locations at two depths using stacked point thermocouples for DTS verification. DTS systems allow the application of this technique over large areas and for long time intervals. In this demonstration, the temporal resolution of the technique is on the order of several hours, depth resolution is on the order of one centimeter, and spatial resolution is one meter. We present results showing the formation and offshore migration of a subaqueous sandbar inferred using both types of buried temperature sensors ground-truthed to regular bathymetric sonar measurements.