A view of the flooded High Street of Yarm c1900. In historic times the river may have served a defensive purpose but it has also caused problems, covering the town on several occasions. Notable floods occurred in Yarm in 1753, 1771 and 1783. In the more recent views of the Town Hall on the south side there are marks showing the the height of the water in the worst of the floods. The lowest mark is from 10th March 1881 and the highest one is from 17th September 1771. The date on the weather vane on the Town Hall is 1710 but some of the buildings in Yarm are much older. 
Picture Stockton Archive
A Pictorial History of Stockton-on-Tees
I was told that the people living near the once tidal River Leven are seeing their properties flooded since the Tees Barrage created a lake 11 miles upstream from the Tees Barrage. Probably why the Leven Road Bridge was nearly washed away, all the melted snow has to go somewhere.
Aye, the Tees was still tidal in Yarm in the 18th century, but it was still tidal in the 20th century too! We would sometimes run the boat up there on a high tide, then all the way down to the estuary and back up to Thornaby, just for a day out.
In the 18th century the River Tees was still tidal at Yarm.
The first major flood in the 1700s was 7 February 1753. One reference says that the water rose to 15ft above High Water mark.
There was less serious flooding in 1761, but the main event was November 17th 1771. This was 5 ft higher than in 1753, and in some places the water was 20ft deep!
In the early 1800s the “Newport Cut” removed a major meander in the River Tees, this allowed water to flow away more quickly, reducing the risk of flooding at Yarm.
Can you please tell me what height the flood water reached in Yarm during the 18th century?