Dredging of the harbor is required because of the constant easterly movement of sand along our coast and thus, across our harbor entrance. Such movement is generated by the ongoing forces of waves and currents. The amount of material moved and deposited is directly proprtional to the serverity of current and wave conditions. This constant movement of masses of sand is termed littoral drift.

Littoral Drift Diagram
(click to zoom in)

    Sand indicated by orange dotted areas, is carried down the San Lorenzo River and thence moved down-coast by wave and tidal action called littoral drift. Constantly moving, the sand mass builds up against the west jetty and flows around it, shoaling the Santa Cruz Harbor entrance channel.  Impeding sand is then dredged from the entrance channel and deposited in the inter-tidal zone where the existing littoral drift carries it down-coast, nourishing those beaches east of the Santa Cruz Harbor entrance.

    Because of sand incursion at the mouth of the harbor, it is essential that an annual dredging effort be maintained to assure sufficient depth at the harbour entrance to permit the safe passage of vessels transiting the entrance.  Shoaling conditions caused by littoral sand drift produce dangerous and unpredictable breaking wave formations at the harbor's entrance.  These breaking waves are extremely hazardous to incoming, and outgoing vessels and pose a particular danger to individuals walking on either of the jetties.