WetSlipFinder
Marine Navigator AI Pro

Fixed Bridge Clearance Checker

Bridge clearance database not connected

When NOAA Coast Pilot / USACE bridge data is connected, we will return: every fixed bridge on your route, its charted clearance, tide-adjusted clearance, and whether you can transit. Until then, treat fixed bridges as 'clearance unknown' and call the bridge tender on VHF 13/16.

Warning levels we will surface

  • No fixed bridge on route
  • Fixed bridge detected — clearance > air draft + 3 ft
  • Fixed bridge detected — marginal clearance, tide-dependent
  • Clearance unknown — do not proceed without confirmation

Fixed Bridge Clearance Planning for Boaters

The Fixed Bridge Clearance Checker is a planning aid that compares your vessel's true air draft against the charted vertical clearance of fixed bridges on your route. A fixed bridge does not open. If you arrive and discover your mast, antenna, radar arch, hardtop, or outrigger is taller than the bridge, your only options are to turn back, unstep the mast, or wait for a lower tide — and on the ICW that can mean hours of lost time or an unsafe anchorage.

Charted clearance is usually measured at Mean High Water. Real-world clearance changes minute by minute. A spring high tide can reduce a posted 65 ft clearance by 2–3 ft. Heavy rainfall on rivers and inland waterways can raise the water level even more. Wind setup, storm surge, recent dredging, and bridge settlement all shift the actual number. Always add a safety margin of at least 2–3 ft above your tallest fixed object — including VHF whip antennas, anchor lights, wind instruments, and any newly installed radar or satellite dome.

To use the tool, enter your vessel's true air draft from the waterline to the highest fixed point, with normal fuel and water loads. The checker will flag bridges along your intended waterway as clear, marginal (tide-dependent), or clearance unknown. We never invent a clearance number. If the bridge tender, NOAA Coast Pilot, and USACE bridge tables do not agree, we mark the segment unknown so you know to call the bridge on VHF 13 or 16 before committing.

For a complete passage plan, pair this checker with our boat route planner, hyperlocal waterway pages, our boating safety guide, and our wider AI boating tools. In a hard-aground or fender-down situation, jump straight to the maritime emergency contacts.

Safety reminder: always verify fixed-bridge clearance against the current NOAA chart, the latest USACE bridge tables, and a live VHF call to the bridge tender. Treat this checker as a planning aid, not a guarantee.

FAQ

How do I measure my boat's air draft accurately?

Measure from the static waterline to the highest fixed object — antenna tip, anchor light, or mast — with typical fuel, water, and load. Round up, never down.

Why does tide change fixed bridge clearance?

Charted clearance is measured at Mean High Water. A spring tide, storm surge, or heavy river flow raises the water surface and reduces the gap under the span.

What if a bridge clearance is unknown?

Do not proceed. Hail the bridge tender on VHF 13 or 16, or call the marina or Coast Guard sector office for a current reading before committing to the transit.