The falls follow an unprecedented period of wet weather in Cornwall, and the county council is urging walkers to take extra care. There are currently 18 footpath closures on the South West Coast Path alone, and many may still be closed during the holiday season.
The area from Lizard to the Tamar is the most badly affected.
Police say around 50 people will be taking part in a co-ordinated search for missing teenager Jordan Cobb this morning.
Staff from the coastguard, Devon & Cornwall Police and Ministry of Defence Police will be scouring both sides of the River Tamar and the dockyard.
They're asking people to stay away from the foreshore and not to go out in boats, as they say it's not safe and will hamper the investigation.
The Devon search will go as far as the citadel, with the MOD searching the dockyard. On the Cornish side it will go from Mt Edgecumbe to Millbrook, including the St John’s and HMS Raleigh areas.
South West Water has been fined more than £16,000 for polluting the Tamar estuary.
The Environment Agency brought the case after partly treated sewage was released from the Camels Head treatment works in Plymouth in February last year.
South West Water admitted four offences of discharging noxious matter.