The Victorian attitude was to cut the loops off! This 1889 plan shows the new course of the river after the cuts as well as where the old loops used to be. Such loops are known as ‘meanders’. These meanders were difficult to navigate, and sail, horses and even manpower were some times needed for the larger ships to get round them. 
Picture Stockton Archive
A Pictorial History of Stockton-on-Tees
This picture is confusing and needs to be rotated by 90 degrees anticlockwise to put north at the top. However, the customs house for the River Tees, used to be situated on the crown of the old meander, where the word “Portrack” is written. When the Customs House was built, Stockton would have been the first port on the Tees, since there was absolutely nothing downstream.It was an easy place to stop ships since they had to be “racked” or dragged up the meander by men. This is supposed to be the origin of the name Port-rack….but equally believeable would be “Port-track”….track to a port (or customs house).