Last year's flood was the most expensive natural disaster in Canadian history but for the environment, it wasn't all bad news.

Many people lost their homes in the disaster and communities like Exshaw, High River and Calgary are still recovering. While mud and silt destroyed many areas, new gravel bars formed along rivers like the Bow are giving some plants the opportunity to flourish.

"We think of this as the silver lining project," said Stewart Rood, a river scientist with the University of Lethbridge ."The silver lining is that the floods are not only natural but they're beneficial and even essential for some of the river valley organisms. Through Calgary and downstream and upstream, the river valleys support cottonwood trees ... these particular trees are dependant on flood events for their reproduction."

Rood says leaf litter provided by trees like cottonwoods help sustain aquatic ecosystems — in other words, being able to fish for trout in the rivers depends on cottonwoods keeping the fish population happy and healthy.

He says the trees also intercept and absorb contaminants in the rivers such as pharmaceutical drugs, which water treatment plants can't remove.

Alberta Environment is working with dam owners and operators in river valleys to ensure river flows are high enough that cottonwood saplings can survive.

However, they won't be deliberately causing floods.