Locks
When the Irish Canals were first built, many discussions ensued about lock sizes.
In 1756 when work commenced on the Grand Canal near Sallins, the original Locks were 42m by 6m (137ft by 20ft). These were deemed too large and reduced to a new standard size for the Grand Canal that accommodated a Canalboat of 18.8m by 4m (61.75ft by 13.25ft). Locks on the Royal Canal are 21m long (70ft approx).
In order to be able to navigate all the southern canals, the Barrow Line, Grand, Naas/Corbally and Royal, trading Canalboats and today’s ‘Widebeam’ barges have dimensions of up to 61.75ft by 13.25ft, these boats fill the width of the Locks.
Navigation
The width of water referred to as the Navigation, is where boats can move without touching the canal bed or the banks. The width is measured across the bed of the canal, not on the surface. The navigation needs to be around 9.3m (30ft), a width that allows two Irish Canalboats or two Widebeams to pass each other safely. This takes into account two boat widths, an allowance of a couple of feet in between boats when passing and leaving a foot or so to avoid hitting the banks at their base. It is also important that moorings posts are installed at locations that leave sufficient room for two boats to pass adjacent to a moored boat.
Maintaining Width & Depth
In recent times, there have been some decisions and proposals that endanger the width and depth of our canals:
- Reed fringes have been allowed to grow at narrow stretches, reducing the width of the navigation. Boats, crew and wildlife can be injured when skippers are forced to drive into the reeds to get out of the way of an oncoming boat. Reeds on a canal, a constructed waterway, can also be an impediment to people getting ashore, quickly and safely.
- Proposals to widen the Greenway and narrow the navigation have been suggested without considering boat traffic.
- Weed, especially invasive weed, has been allowed to grow and spread in the waterways. This is an obstacle to boating, especially during the spring and summer months.
- Silt amasses on the bed of the canal, from faulty feeders and incoming drains, and the debris deposited when weeds die back in winter. These alluvial conditions prevent a boat’s propulsion, and make it difficult for a skipper to steer in the right direction.
- Slanted banks that reduce depth at the edge of the navigation, create an obstruction, cause boats to run aground on the banks and moored boats to keel over when the depth drops.
Necessity
Having a navigation channel of the right width and depth on the canals is vital for safety. A boat can only be steered safely when there is sufficient depth and width of clear water around the propellor. Survey Report
