The Whitesands project would see the creation of a raised walkway along the waterfront area.
The scheme has been revised a number of times to address public concerns about the river view and loss of car parking.
Last year an estimate of project costs put the overall bill at between £15m and £17.8m.
The Scottish government would provide 80% of the funding for the scheme with the remainder coming from Dumfries and Galloway Council.
It has already approved nearly £4.5m towards the project which means it has a maximum of about £500,000 to find.
A report to the local authority will ask it to agree that the project be officially published and adopted as a flood protections scheme.
It cites a range of reasons for the increased costs which include:
The council has spent nearly a year refining the scheme which it said had produced a range of "positive developments".
Those actions include:
Councillor Colin Smyth said: "I am pleased that we are now at the stage to seek committee agreement to commence the formal process of publishing the Whitesands project as a flood protection scheme.
"It is unacceptable that the largest town in our region continues to flood.
"That is why all councillors agreed for a flood protection and regeneration scheme to be progressed for the Whitesands, demonstrating the need for change and putting an end to the regular flooding that has plagued our regional capital for too long."
He added that it was more than a flood protection scheme and could create a "high quality public open space" to encourage the use of the Whitesands.
A major flood protection scheme in Dumfries is set to make a step forward but has seen its cost estimate rise significantly to £25m.