The landowner, who wishes to remain anonymous, said the off-roaders have been trespassing through fields belonging to him and other nearby residents to access the River Onny north of Bishop's Castle.
He said the motorists "rip up the river" and damage the environment.
The landowner said: "I've had a lot of problems with people driving across my land and down the riverbed.
"About a fortnight ago we had them all in the river. They're not official off-roaders, they are a group that drive around on these green lanes causing havoc and damaging the river.
"They've come across my land before to get there. There's two fords across the River Onny and these chaps come down, cross the ford but turn right and drive right down the river.
"They're making a nuisance of themselves – a week or so ago they actually broke down in the river.
"It's been happening on and off for quite a long time. Normally we don't catch them but I know they've been spotted a couple of times.
"It's an environmental nightmare because they're damaging the riverbed, the fields and all the fish and animals that live there.
"They rip up the river and need to know that what they're doing is causing damage."
This comes after the Environment Agency issued a warning on Wednesday to a fleet of vehicles spotted driving down the river, stating that they could be subject to legal or civil proceedings.
Chris Bainger, fisheries technical specialist with the agency, said he feared other off-roaders may cause similar damage as people venture further through the county as lockdown restrictions are eased.
Mr Bainger added the vehicles are "damaging the sensitive gravel on the riverbed" and less fish will be able to live in the water.
Anyone who is found to have driven along a river could be subject to criminal proceedings under the Wildlife and Countryside Act or civil proceedings for trespassing.
The Environment Agency is investigating the incidents and is encouraging anyone with information to contact West Mercia Police on 101.
Alternatively, contact Crimestoppers anonymously on 0800555111 or crimestoppers-uk.org