Plans to deal with a river which has diverted itself are being considered by the Environment Agency and a town council.
Earlier this year during the Beast from the East, the River Thet, which flows through the town before joining with the Little Ouse, breached a bank.
The majority of the flow now follows a path parallel to the original path and joins the Little Ouse at the Pulp Mill.
The change in the flow has led to low water levels at the Coffee Mill - down around 20cm in average from last year - contributing to 300 fish dying in the summer due to low dissolved oxygen levels.
Thetford Town Council, which owns the banks of the river, is working with the Environment Agency to decide on next steps to return the water levels at the Coffee Mill to normal.
The Environment Agency said it is considering 'all sustainable options', including modifying the bank to limit flows and a feasibility study is due to take place later in November.
Cash to fix the problem will come from Water Environment Improvement Funding, with the town council also likely to have to pay for any work.
A spokesman for the Environment Agency said: 'We are assisting Thetford Town Council (the riparian owner) to find a solution which is favourable in terms of offering flood protection and biodiversity benefits.
'We will be contributing some Water Environment Improvement Funding to investigate potential options which keeps free movement for fish and eels, enables effective management of the river and retains flow through Coffee Mill sluice.'
She added: 'All sustainable options are being considered including the modification of the bank to limit flows and increase upstream retention levels.
'The feasibility study will be undertaken later this month so it is hoped that costed options can be explored by early December. We will then work with the town council on the public consultation and agree on preferred options.'
Thetford Town Council has said options for solving the issue will be put to the Amenities, Land, and Property Committee.
A spokesman said: 'The Environment Agency has some funding available this financial year to address the problem and is currently working with consultants to determine the feasibility of several options.
'Depending on the final option and cost, we hope to implement it before the end of March 2019.'
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here