One resident, who regularly walks along the canal, said: “Keddington Lock being partially blocked with weeds and tree saplings, growing in it.
“This is restricting the flow and in times of flood, when all debris that flows downstream - including the huge volume of watercress weeds further upstream that would be washed downstream - would be caught in this trap and cause even greater blocking for water flow.
“The canal may be wider than the Lud, but it still floods and I regularly get the emergency phone call to warn of danger of flooding from the canal.
“I walk down the canal in Louth most days, and it is a fact that the maintenance to clear weeds and debris has got worse over the last few years.”
The Environment Agency (EA) denied claims that they were not giving sufficient concern to the canal - and reassured residents that it is monitored.
An EA spokesman said: “We take all complaints and queries from members of the public very seriously. Our officers are very aware of the concerns of local residents following the flood in the town in 2007.
“We want to reassure that we conduct regular channel inspections of the River Lud and Louth Canal.
“Our officers monitor the watercourse and carry out a comprehensive annual maintenance programme of work.
“This includes a combination of both hand and machine work to remove obstructions we consider will restrict flow and increase flood risk. The derelict Keddington lock structure is one of a number of similar structures along the Louth Canal that we monitor to ensure it carries water effectively.
“We carry out our annual maintenance programme, but only remove trees and vegetation that we consider to pose an unacceptable risk.”