Tidal Gates for Small-Boat Routing

Some routes are not open all day.

They have gates.

A tidal gate is a window where tide, current, depth, and sometimes wind-against-current risk make a passage reasonable. Miss the window and the same route can become slow, shallow, uncomfortable, or unsafe.

Small-boat routing has to understand that time constraint.

Depth Gates Are Obvious

The easiest tidal gate to understand is depth.

At low water, a shallow pass may not have enough under-keel clearance. At higher water, it may become usable. Later, it closes again.

That makes waiting a valid routing action.

A route engine should be able to say the route is blocked now but likely available after the water rises.

Current Gates Are Less Obvious

Current can create a gate even when depth is fine.

Against current, a slow boat may make poor progress. Across current, it may need a large correction. With wind against current, sea state can become steep and uncomfortable.

The route may still exist on the map.

The boat may not want to be there.

Gates Are Local

Tidal behavior changes by channel, coast, estuary, and pass.

A general tide table is useful, but it does not automatically describe every route segment. The routing system needs location-aware tide and current context, and it needs to keep confidence conservative where local data is weak.

The Best Route Might Include Waiting

Many route planners treat waiting as failure.

For sailing, waiting can be seamanship. It can turn an upwind slog into a fair current. It can add depth margin. It can avoid a bad wind-against-current window.

A useful route plan should explain the wait reason.

Not just "depart later," but "depart later because the tidal gate opens and under-keel clearance improves."

Timing Is Navigation Context

HECTOR's route work is a reminder that marine planning is four-dimensional.

Latitude, longitude, and depth are not enough. Time changes the water.