I work at a facility that handles large barges, as well as ships. With the ships, tugs are the main force finessing it into place but also the ships own power source can be used to reverse thrust and ‘apply the brakes’.

The barges are likely more similar in size to that of ships in times before tugs were around to help. Assuming the weather is not too rough (wind can wreak havoc in the process, and it’s more safe for them to be at open sea than to attempt a landing) the barge approaches the dock very slowly, and the tug that has towed it there is also a factor here but the large, heavy ropes that are used to tie the barge up to the dock can be used to ‘apply the brakes’. These ropes are attached to the barge, and a worker on the dock puts a wrap or two around a cleat and is able to apply enough tension in the rope so that it slips just enough for the situation. If he holds the tail of the rope taught, the knot on the cleat gets tight, and the rope gets tight and stretches (the diameter of the rope might be 4 inches in its static state, and as it stretches, the diameter reduces dramatically…. This always freaks me out because I know that if the rope breaks under this kind of stress, it’s like a rubber band on steroids and can literally cut a man in half) as the barge slows down. He can loosen his grip and allow more rope to slip if necessary.