Hydrology: Attributes of a Healthy Stream

An alluvial stream is one whose channel is composed of the sediments transported by the stream itself and that generally changes the shape of its bed as the rate of flow changes. (Adapted from Attributes of an alluvial river and their relation to water policy and management by Trash, McBain, and Leopold).

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Attribute Three (Part A): The Stream has Access to its Floodplain

Access to the floodplain means a stream is connected to its floodplain. This is one of the most important requirements for a healthy stream. In situations where this connection has been lost, the stream channel becomes incised or deepens to a level well below the level of the floodplain. When floods are no longer able to expand onto the floodplain, streams focus their power and erosive energy on bank margins, disrupting the balance between water yield and sediment load that characterizes a stable stream.

Streams are affected by the loss of connection because pools fill in, banks become unstable, and the stream begins an alternating pattern of incision and channel braiding. Floodplains are affected because they dry out and are no longer scoured by periodic floods. One of the Tribes' key restoration strategies on the Jocko is to raise the river by adding fill or moving the channel to pre-disturbance locations, where it can access its floodplain.

  • In a stable, healthy channel that is connected to the floodplain, floods have access to the floodplain and the channel is free to migrate.

  • In an incised channel (one that has deepened below the level of the floodplain), floods cannot expand onto the floodplain.

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How a healthy steam functions during a riparian flood. The water moves across the riparian zone.

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How an incised steam functions during a riparian flood. The water cannot access the riparian zone.

Hydrology: Attributes of a Healthy Stream

An alluvial stream is one whose channel is composed of the sediments transported by the stream itself and that generally changes the shape of its bed as the rate of flow changes. (Adapted from Attributes of an alluvial river and their relation to water policy and management by Trash, McBain, and Leopold).

My Image

Attribute Three (Part A): The Stream has Access to its Floodplain

Access to the floodplain means a stream is connected to its floodplain. This is one of the most important requirements for a healthy stream. In situations where this connection has been lost, the stream channel becomes incised or deepens to a level well below the level of the floodplain. When floods are no longer able to expand onto the floodplain, streams focus their power and erosive energy on bank margins, disrupting the balance between water yield and sediment load that characterizes a stable stream.

Streams are affected by the loss of connection because pools fill in, banks become unstable, and the stream begins an alternating pattern of incision and channel braiding. Floodplains are affected because they dry out and are no longer scoured by periodic floods. One of the Tribes' key restoration strategies on the Jocko is to raise the river by adding fill or moving the channel to pre-disturbance locations, where it can access its floodplain.

  • In a stable, healthy channel that is connected to the floodplain, floods have access to the floodplain and the channel is free to migrate.

  • In an incised channel (one that has deepened below the level of the floodplain), floods cannot expand onto the floodplain.

My Image

How a healthy steam functions during a riparian flood. The water moves across the riparian zone.

My Image

How an incised steam functions during a riparian flood. The water cannot access the riparian zone.

Hydrology: Attributes of a Healthy Stream

An alluvial stream is one whose channel is composed of the sediments transported by the stream itself and that generally changes the shape of its bed as the rate of flow changes. (Adapted from Attributes of an alluvial river and their relation to water policy and management by Trash, McBain, and Leopold).


Attribute Three (Part A): The Stream has Access to its Floodplain

Access to the floodplain means a stream is connected to its floodplain. This is one of the most important requirements for a healthy stream. In situations where this connection has been lost, the stream channel becomes incised or deepens to a level well below the level of the floodplain. When floods are no longer able to expand onto the floodplain, streams focus their power and erosive energy on bank margins, disrupting the balance between water yield and sediment load that characterizes a stable stream.

Streams are affected by the loss of connection because pools fill in, banks become unstable, and the stream begins an alternating pattern of incision and channel braiding. Floodplains are affected because they dry out and are no longer scoured by periodic floods. One of the Tribes' key restoration strategies on the Jocko is to raise the river by adding fill or moving the channel to pre-disturbance locations, where it can access its floodplain.

  • In a stable, healthy channel that is connected to the floodplain, floods have access to the floodplain and the channel is free to migrate.

  • In an incised channel (one that has deepened below the level of the floodplain), floods cannot expand onto the floodplain.

My Image

How a healthy steam functions during a riparian flood. The water moves across the riparian zone.

My Image

How an incised steam functions during a riparian flood. The water cannot access the riparian zone.