Thousands of fish have been killed after 600,000 tonnes of untreated sewage was forced into the Thames during Tuesday's storms.
Plans for a solution to drainage problems have been developed
The Environment Agency said the dead fish were visible in the river at Kew, Brentford and Isleworth in west London.
It said the sewage, which flowed into the Thames due to inadequate drainage systems in London, used up the water's oxygen reserves, killing the fish.
A clean-up operation is under way to stop more bream and roach dying.
Thames Water has launched its oxygenating vessels which help improve the quality of the water.
Andrew Boyd of Thames Water said the company had been working with the Environment Agency to come up with a long-term solution to the problem.
He explained that London's Victorian sewers pushed water into the Thames instead of allowing it to flood homes and streets.
Mr Boyd told BBC News Online: "Everyone agrees that any solution to this will be a massive engineering scheme.
"We have worked with the Environment Agency and other agencies to produce a report for the government suggesting how the problem can be solved.
"We are waiting to hear from the Department of Environment, Food and Rural Affairs how they are minded to deal with the problem."