Experts have put forward radical plans for a "blue belt" to protect Derby residents from future floods.

The Environment Agency says widening the flood plain along the lower reaches of the River Derwent to create a blue corridor at least 120 metres wide will boost flood protection for thousands of homes and businesses.

Allowing the river to rise and wash over a wider plain is among a raft of ideas aimed at protecting the area as its ageing flood defences reach the end of their design life and climate change increases the flood risk.

Innes Thomson, Environment Agency area flood risk manager, has said: "We want to provide modern standards of flood defence along the Lower Derwent as soon as possible and, working with other authorities, help people to better understand how they can improve their resilience to flooding in general."

She adds the agency believes the options in the draft Lower Derwent Strategy "represent the most effective way of protecting the area into the future".

The agency also proposes opening two of the five Derby Junction Railway Bridge arches to improve water flow through the city centre. Other long term plans include changes in land management to increase water retention time.

These could mean changes to farming practices, less upland grazing, more woodland, the restoration of peat moorlands and the creation of wetlands.

Other options for tackling the flood risk including up-stream storage, flow diversion, dredging, underground tanks and river widening were dismissed as too expensive and not protective enough.

The blue corridor proposal will also boost wildlife habitats, river access and recreational use, it is claimed.

Experts point out that with climate change and rising sea levels building homes on floodplains is no longer viable.

Lucy Care, city council cabinet member for planning and transportation, has said: "It would be very irresponsible not to be looking at the increased flood risk and working with the Environmental Agency to provide defences."

Work could begin within five years if funding is found.

But the scheme has disadvantages including affecting existing land use and properties and curbing development and regeneration possibilities in the blue corridor.

John Gosden, a senior consultant at Jacobs, will present a paper on the plans at the Chartered Institution of Water and Environmental Management's (CIWEM) annual conference in London in April.

He said: "This is the first time that this scale of change has been attempted in England and provides valuable lessons that can be transferred to other locations."

For conference details go to website www.ciwem.org/events.

David Gibbs