As flooding continues in Ottawa along the Rideau River, local conservation authorities are working to update floodplain maps last completed in the 1980s and early 1990s.

The Rideau Valley Conservation Authority warned Thursday that water levels are expected to increase 10-15 cm over the next 24 to 36 hours in Old Ottawa South and in the southern stretch of the Rideau River from Manotick to Beckett's Landing.

The South Nation and Mississippi Valley Conservation Authorities have also released updates for their watershed regions.

The three Ottawa-area conservation authorities base their flood predictions on floodplain maps, but many maps around the province and country are woefully out-of-date.

That's why last year the city helped fund five-year projects to update the maps in all three regions.

RVCA engineer Ferdous Ahmed said updating the maps is not just for predicting spring runoff.

"It helps people to not build their houses here. Because that's risky," said Ahmed.

University of Waterloo professor Blair Feltmate commends the city for helping to fund the update to the maps, but said mapping should go beyond capturing today's lay of the land.

Feltmate said they should try to project how water might flow in big, unpredictable storms expected in the future.

Last fall Feltmate co-authored a study that found insurance executives would not offer comprehensive flood insurance in Canada unless new maps of flood-prone areas are made that take climate change into account.

"When you're building infrastructure, roads, bridges houses, buildings, whatever, they're there for the next 20, 50, 70 years," said Feltmate. "And if we put them in the wrong spot, we've wasted the whole effort."

Feltmate said water damage is very costly, and Canada needs to do a better job in figuring out how to prevent it in the first place.