Blockages along 300 kilometres of West Yorkshire's rivers are to be tackled this winter to reduce flooding.
Staff from the Environment Agency doing an annual clearup will inspect the watercourses, looking for objects that could cause flooding problems.
Potential hazards include fallen trees washed downstream and man-made problems such as abandoned vehic
les or flytipped waste.
The Environment Agency's operations staff tour all the main watercourses between November and March and remove obstructions that can safely be pulled out of the river.
Objects such as trees and large flytipped items cannot be easily dealt with, so staff return later with lifting equipment.
Environment Agency operations manager Peter Holmes said: "We keep an eye on watercourses throughout the year looking for potential flooding problems, but in the winter we carry out intensive inspections.
"Sometimes we can clear blockages easily from the bank, but there are lots of other things that need more time and care.
"For example, large trees need to be carefully lifted from the channel and cut up into movable chunks. Dumped vehicles can cause serious pollution problems if the petrol tank ruptures or oil escapes, so we need to be very careful there."
Potentially dangerous waste such as unlabelled drums or clinical waste needs to be removed carefully and investigated for disposal.
Mr Holmes said: "The build up of waste in our rivers is not just unsightly, it can also greatly increase the risk of flooding."
Environment Agency staff have carried out CCTV inspections of some underground culverts and removed potential blockages.
Anyone who sees large obstructions can ring the agency on 0800 807060.
