In 2007 the regional council took responsibility for flood risk management through the city and vegetation control from WDC.
It is proposed Horizons should now take are of channel training and erosion protection structures along the south spit and the south and north mole to its current function.
WDC would continue to have responsibility for port infrastructure, the turning basin, stormwater outlets and boating infrastructure.
Mr Gordon said the Whanganui River needed to be brought in line with how rivers were managed across the region.
"I'd really like to get it tidied up," he said.
Mr Gordon said that would allow much needed maintenance to be carried out without debate over who was responsible.
"This report highlights there's some serious deferred maintenance," he said.
"If something was to happen in a storm event and there was a breach of the south spit it would be catastrophic, especially for the people of Balgownie.
"Those walls weren't designed for seawalls hitting them."
Whanganui mayor Hamish McDouall said he was pleased the issue was moving forward.
Meanwhile, the two people who are to represent Te Awa Tupua - the Whanganui River's legal personhood - are yet to be announced.
An announcement has been expected for weeks but neither the Minister for Treaty of Waitangi Negotiations or Whanganui iwi returned calls on Thursday.
