A method and apparatus for measuring bottom scour adjacent a foundation structure extending into the bottom of a stream of flowing water is disclosed. An elastic wave source is used for transmitting elastic waves through the water, the scour zone, and the bottom adjacent the foundation structure. The elastic waves are transmitted directly to an array of receivers and indirectly through the foundation structure to produce refracted signals that also travel to the receivers. The array of receivers are adapted for substantially vertical positioning such that a portion of the receivers will sense elastic waves that travel through the water above the scour, a portion will sense elastic waves that travel through the scour, and a portion will sense elastic waves that travel through the bottom adjacent the structure. Means are utilized for recording the time required for the elastic waves to reach each receiver to measure the depth of scour next to the foundation structure. The soil profile is deduced by using the known velocities of elastic waves in concrete, water, mud slurries, and soil, as appropriate to determine the amount of scour around the foundation structure.