Canals and Locks
Boat captains at times need to navigate their boats, ships or any watercraft vessel from one stretch of water to another.
These river and canal waterways have different water levels. The functionality of a lock is a cavity that allows water levels to be varied. Different from a caisson lock, a canal inclined plane or boat lift. The chamber itself, known as caisson, rises and falls.
Locks allow easier navigation through rivers. They also enable a canal to pass over land that is not level enabling a much more direct route to be taken.
What is a pound lock?
These days a pound lock is used the most on canals and rivers. Pound locks have gates on both ends that control the level of water within the cavity. The original design had a single gate called a flash lock.
Pound locks are not what you call a modern-day navigational feat. They were first used in medieval China during the Song Dynasty between 960-1279 AD. Qiao Weiyue, a Song politician and naval engineer is credited for the waterway navigational advancement that replaced slipways that for most part caused only problems for vessels.
The pound lock chamber was covered with a shed like roof. When the hanging gates closed, water rose up like the tide until the proper water level had accumulated. After the vessel passed through, the gates were opened, and the water flowed out.
Water levels could vary between 4 or 5 feet at each end of the lock.
The level in the Grand Canal was raised 138 feet.
A lock can be required in a stretch of river to overcome obstacles like mill weir, dams or rapids.
Weirs and locks are used together in larger scale river navigational enhancements. The weir will increase the depth of the water in a shallow stretch. The necessary lock would be built in the weir gap at the end of an artificial cut downstream. This circumvents the weir and possibly the shallow stretch of river underneath it.
When this is done to a river it is commonly referred to as a Waterway or River Navigation.
By building a sea lock into the estuary, a river can be made non-tidal. Locks are required in advanced river navigations.
Flood locks protect the upstream end of the cut in the case of a longer cut circumvention around the stretch or river.
Longer cuts create a greater difference in the water level of the river between the beginning of the cut and the end of the cut. This allows more locks in its length making the cut, with this effect, a canal.
With the necessary changes needed in water levels, without detours that are economical in time travel and building costs, locks are imperative.
Still today construction techniques improve, and engineers find more ways to cut through and across barriers. Cuttings, long tunnels, embankments or aqueducts and technical devices like boat lifts or inclined planes are constantly improving. Locks are essential today in the most modern waterways where navigation is necessary. They continue to be built as a waterway solution between bodies of water and land.