Idaho Fish and Game biologists are applying techniques to restore salmon and steelhead habitat that can reduce the effects of large flood events while also improving agricultural lands. The way this is done seems counter-intuitive: by allowing rivers to flood into areas where they will not cause damage.
During spring floods and large rain events, rivers naturally spill over their banks, creating floodplains and wetlands that provide critical refuge and food for juvenile salmon and steelhead. As this water moves away from the river and slows, fine nutrient laden sediment is deposited, enhancing vegetation in the floodplain. These processes can both irrigate and fertilize agricultural lands.
Floodplains that are allowed to flood regularly can absorb immense amounts of water and have a proven history of lessening large flood events. During historical floods, it is not uncommon to see flows halved downstream of active floodplains. Water that is absorbed by these lands recharges aquifers and can provide springs that enhance stream flows into the dry season.
IDFG restoration biologists are actively working on restoring floodplains in order to improve juvenile salmon and steelhead survival. In some rivers in Idaho, a lack of juvenile rearing habitat is a major factor limiting their recovery. Activating these floodplains would supply necessary refuge for juvenile salmon and steelhead, who require slow-moving habitats to shelter and grow in.
Although these projects are a clear win-win scenario, they have been difficult to implement due to outdated ideas about flood control. This is an important time to share information about this topic so that we can help recover wild salmon and steelhead populations in ways that protect communities from future floods.
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