Tides
What a tide window actually costs a small harbour
At a locked harbour the published timetable is only the start. The real window is the published gate, minus the minutes the lock keeper needs, minus the minutes a late coaster stole from the previous lock, minus the minutes a yacht club race dumped into the waiting pontoon.
We once sat with a clerk who insisted the harbour ‘always had two hours’. The movements book showed forty-minute clusters around springs and a ragged hour at neaps, with a long tail of vessels that arrived on the tide and then waited for a berth the chart later proved was occupied by a fishing boat that had not been booked.
The cost is not theoretical. A tug on stand-by is charged. A crew that misses the next rise stays alongside and eats into the next day’s slot. A bunker barge that cannot come on the window leaves a vessel unfuelled, which then occupies the berth through a second tide. Occupancy charts that ignore the gate treat those extra hours as demand. They are residue.
A tide-window briefing is therefore a stubbornly local document. We want the cill height in writing, the lock standing orders, and a season of calls. We do not substitute a beautiful average. If the harbour’s own custom is to refuse commercial traffic after 16:00 in winter, that custom belongs on the page.
Committees sometimes hope the briefing will recommend a new lock regime. It will not. It will show which windows were used, which were missed, and which delays sit against weather rather than the gate. Decisions about hours and staffing stay with the people who employ the lock keeper.