This plot of Acoustic Doppler Current Profiler (ADCP) backscatter intensity illustrates the challenges inherent in deploying instruments on the seafloor in an area of active sediment deposition.
Four days after being deployed in 40 metres of water near the mouth of the Fraser River, the ADCP platform was flipped upside-down, presumably by an underwater landslide. The value of instrument roll goes from near zero to its minimum value of -24 degrees, and simultaneously the pressure jumps by about half a metre.
The image of the tidally-varying ocean surface is much fainter (and slightly further away) after the landslide because the ADCP’s acoustic signal now must bounce off the bottom (visible as the very strong echo at 1 metre range) on its way to and from the surface of the ocean.
