A 100-metre long carpet of flotsam and jetsam was brought in this week by the highest tides of the year, captured by the flood gates and leaving visitors recoiling in disgust.
Car tyres, plastic bottles and footballs - even an old cupboard unit - float amongst the branches and winter vegetation from the annual storm season along the banks of the River Ribble.
One walker, on a trek around the dock estate, said: "It looks absolutely awful. I can't believe no-one is trying to clear it up.
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"What image does it create for visitors to our city?"
But the simple truth is - it happens every year and has been doing for almost 130 years.
"The Victorians knew what they were doing when they built the storm gates opening outwards," said Steve Miller at Preston Marina.
"It has been happening every year since 1892. Every single winter, when we get the high tides and the storms, this is what happens. That's why the gates are there."
This week saw the highest tides of the winter, rising to 10.2 metres. As heavy rainfall added to the Ribble's swell, the debris washed from the banks collected at snagging points along the river, with the entrance to Preston Docks providing a perfect man-made trap.
Steve Miller explained: "The vast majority of this is Mother Nature's branches and twigs which fall down in the winds and get into the river.
"It is inevitable with high winds and high tides that this stuff will get trapped where it does, in all the nooks and crannies it can find.
"That's why the gates are called storm gates and that's why the Victorians built them like they did.
"But it is also inevitable that the debris will go like it has arrived. As the tides drop it is left on the river banks or gets dragged out to sea.
"To be honest I wouldn't say this year is anything exceptional - I've seen it far, far worse than this."
Preston Council says it has already taken measures to try and flush away the debris and will take more action when the weather allows.
Deputy chief executive and director of customer services Neil Fairhurst said: “The flotsam and jetsam that accumulates in the dock entrance from the river occurs every time there are strong westerly winds and large high tides.
“Action to flush away the built-up debris as and when our water management regimes will allow (depending on the tides and wind conditions) has already taken place this week, and will be repeated when we can.
“The extremely large build-up of debris is the result of three recent very high waters and the gale force westerly winds. Further debris will, of course, be deposited at every tide whilst the current weather conditions continue.”