The Staircase for Giants: Engineering the Welland Canal

This stylized X-ray reveals the hidden engineering of the Twin Flight Locks in Thorold. It shows the massive subterranean culverts
that use only gravity to move 91 million litres (24 million gallons) of water, lifting vessels over the 30-story Niagara Escarpment.

Omg are you kidding me? I’ve walked along the canal so many times (check out some old photos in my Niagara Eh! section), and never fully realized the amazing work that went into the creation of this magnificent engineering marvel! Well I sort of did but not in such depth.

For instance, did you know that the "Fourth Welland Canal" (officially called the Welland Ship Canal—for those pedantic souls who love the blueprints! 🤓) isn't a name for a specific spot? It actually means this is the fourth time around they’ve built the entire system to finally get it right! Since 1824, they've been perfecting this liquid staircase that carries those massive ships across our region.Who knew! I didn't.

The 8-Step Climb

So, before we dive deep, (because even I had this part mixed up), here’s an idea of how the canals all work together to get these ships over the "mountain." To get from Lake Ontario to Lake Erie, a ship has to navigate a series of 8 concrete steps that lift them 99.5 metres (326.5 feet) above where they started:

• Steps 1, 2, and 3 (St. Catharines): These single locks handle the initial climb from Lake Ontario into the city.
• Steps 4, 5, and 6 (The Twin Flight Locks - Thorold): The star of this post! This is the famous "staircase" that does the heavy lifting over the Niagara Escarpment. These are "twinned," meaning ships can actually go up and down at the same time!
• Step 7 (Thorold): The final lift that puts the ships at the very top of the hill (right by the 58 highway!).
• Step 8 (Port Colborne): A massive "Guard Lock"—one of the longest in the world—that levels the ship out so it can safely sail into Lake Erie.

Conquering the "Mountain"

To get a vessel from Lake Ontario up to the level of Lake Erie, it has to be lifted a staggering 99.5 metres (326.5 feet). To put that in perspective, that is like taking a massive steel freighter and hoisting it to the top of a 30-story building! Without this canal, the "Mighty Niagara" would remain a dead end for global trade. Instead, we have this incredible system that carves right through the heart of the peninsula, stretching 43.5 kilometres (27 miles) from Port Weller to Port Colborne.

This illustration reveals the 42.4-metre
(139-foot) climb over the Niagara Escarpment
at the Thorold Flight Locks.

The Staircase of Water

The real "magic" happens at Locks 4, 5, and 6 in Thorold. These are known as the Twin Flight Locks. Unlike the other locks, these are "twinned" side-by-side, allowing ships to pass each other while one goes up and the other comes down. It’s a literal staircase for giants, lifting vessels over the steepest part of the Niagara Escarpment.

 

The Power of Gravity

What’s even more mind-blowing is that the entire system is gravity-powered. There are no massive pumps pushing the water around. Instead, engineers designed a series of valves and culverts that simply let gravity do the work. When a lock needs to be filled, they open the "taps" from the higher level, and 91 million litres (24 million gallons) of water move into the chamber in under 15 minutes.

 

The Giants of the Great Lakes

In my illustrations, you see the massive bulk carriers known specifically as "Lakers." Unlike ocean-going vessels, Lakers are designed with vertical sides and a snub-nosed bow to maximize every inch of the lock’s capacity. A modern "Seawaymax" Laker is 225.5 metres (740 feet) long—nearly the length of two and a half football fields—yet it fits into the lock chamber with only about 30 centimetres (one foot) of clearance on each side.

Engineering Tolerance

This snub-nosed design is a practical solution to a math problem: how to carry 30,000 tonnes (33,000 tons) of cargo through a lock that only has 24.4 m (80 ft) of width to spare. While ocean-going Salties have pointed bows to cut through massive waves, Lakers are designed like massive floating boxes. This allows them to maximize every square centimetre of the lock chamber’s 233.5 m (766 ft) length, fitting as much wheat, iron ore, or salt as humanly possible into a single trip. It is a game of inches where the ship’s hull is designed to perfectly match the canal's concrete walls.

 

Precision and Power

Navigating a 30,000-tonne vessel into such a tight space requires incredible precision from the captain. These ships are essentially floating warehouses; a single Laker can carry enough wheat to bake one million loaves of bread. Because they operate in the fresh water of the Great Lakes, these "Giants" can remain in service for 40 to 50 years, far outlasting their saltwater cousins.

Sofistikateit Visual Archive

"Great Lakes Sailing - Welland Canal HD time-lapse" — Field Research Footage

By the Numbers

 
• Total Lift: Ships are raised 99.5 metres (326.5 feet) to bypass Niagara Falls.
• The Locks: There are 8 locks in total. Lock 8 in Port Colborne is one of the longest in the world at 420.6 metres (1,380 feet).
• Lock Size: Each lift lock is 233.5 metres (766 feet) long and 24.4 metres (80 feet) wide.
• Transit Time: It takes an average of 11 to 12 hours for a vessel to travel the entire canal.

   The Welland Canal isn't just a waterway; it's a 43.5-kilometre (27-mile) testament to human persistence over the rugged Niagara terrain.

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Resources

Great Lakes St. Lawrence Seaway System. (2024). The Welland Canal Section.

Niagara Falls Museums. (n.d.). The History of the Welland Canal.

Infrastructure Ontario. (2025). Engineering Marvels: The Fourth Welland Canal.

St. Lawrence Seaway Management Corp. (2024). The Welland Canal Section.

Ontario Power Generation (OPG). (2025). Sir Adam Beck II Generating Station & Diversion.

The Welland Canal Archive. (n.d.). History and Engineering.