A tide gauge history of more than 120 years provides a remarkable record of response to port dredging at Fremantle. However, dredging impacts have been obscured by long time frames of response, allowing impacts to be ascribed to other factors.
Tidal changes due to dredging are often dominated by changes to instrumentation, or discontinuous records. The extended record at Fremantle shows that changes have taken decades to establish, are spectral in nature, and are often obscured by other factors.
This evaluation inadvertently resulted in identification of declining synoptic surge from the 1930s, distinct from the tidal change.