Allowing flood-plains to be submerged during storms may cut future flood risks

In a new study, scientists in the US have suggested that allowing flood-plains to be submerged during storms would reduce the risk of flood damage in nearby urban areas.

"We are advocating very large-scale shifts in land use," co-author Jeffrey Opperman, a member of The Nature Conservancy's Global Freshwater Team, told BBC News.

"There is simply no way economically or politically that this could be accomplished by turning large areas of flood-plains into parks," he said.
 
"What we are proposing in this paper is a way that this strategy can be compatible, and even supportive, with vibrant agricultural economies and private land ownership," he added.

The authors explained that the flood season and growing season in California did not occur at the same time.

This meant that allowing the land to be submerged by floodwater would not result in a permanent loss of farmland or crops being destroyed.

In their paper, they said that man-made flood management systems, such as levees, also had an ecological impact.

"Control infrastructure prevents high flows from entering flood-plains, thus diminishing both natural flood storage capacity and the processes that sustain healthy riverside forests and wetlands," they observed.

"As a result, flood-plains are among the planet's most threatened ecosystems," they added.

According to the researchers, the reconnection programmes would deliver three benefits, namely, reducing the risk of flooding, increasing flood-plain goods and services, and, providing greater resilience to potential climate change impacts.

Dr Opperman said that the scheme also had numerous additional ecological benefits.

"In recent decades, people began to notice that this area was a phenomenal habitat for birds," he said.

"In the past 10 years, people recognised that native fish were moving from the river on to the flood-plain, and deriving all of the benefits that fish get from natural flood-plains," he added.

According to Dr Opperman, in other parts of the world, there was a range of agricultural strategies for private landowners that would be compatible with allowing areas to be flooded.

"There are emerging markets for ecosystem services, such as carbon sequestration and nutrient sequestration," he explained.

"These are services that flood-plains do provide, so with various climate policies there will be a price for carbon," he said.