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Why is surface flow stronger on one side of a Northern Hemisphere estuary?

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Diagram showing four main types of estuaries: salt wedge, partially mixed, vertically homogeneous, and fjord. Each panel illustrates river and seawater mixing patterns, with arrows indicating the direction of saltwater and freshwater flow. — estuary Four main types of estuaries: (A) salt wedge estuary, (B) partially mixed estuary, (C) vertically homogeneous estuary, and (D) fjord (black arrows indicate salt water and white arrows fresh).

In the Northern Hemisphere, the surface flow in an estuary is stronger on the right-hand side when facing seaward due to the Coriolis effect, which is a result of Earth’s rotation. This phenomenon influences the distribution of water movement within the estuary, causing the bottom flow to be stronger on the opposite side.1