Figure 29. Chirp profile at Port Lambton, Ontario (see fig. 28 for location):  A, lens of sediment deposited in the channel thalweg; B, buried fluvial channel surface; C, first multiple reflection of riverbed. Vertical scale is depth in meters (zero depth is 175.2 m IGLD 1985 based on water level, at the time of data acquisition, at the Canadian Hydrographic Service gage at Port Lambton), using a sound velocity of 1,450 m/s in water and 1,650 m/s in sediment. Click on figure for larger image.