Sedimentation in San Pablo Bay changed dramatically during the past 140 years. From 1856 (the earliest detailed hydrographic survey) until at least the late 1800's hydraulic mining debris filled San Pablo Bay. During the early 1900's sedimentation slowed and, in the late 1900's, San Pablo Bay was erosional as the supply of hydraulic mining debris decreased and Central Valley water projects diminished sediment supply to the Delta and Bay. These pages show change in sedimentation using computer analysis and display of historical hydrographic surveys made by the US Coast and Geodetic Survey (USCGS) and the National Ocean Survey (NOS).