Butano Creek Floodplain Reconnection and Restoration Design

cbec is currently developing designs for a restoration project that will reconnect a one mile incised reach of Butano Creek, a tributary to Pescadero Creek, to its adjacent floodplain.

The objectives of the restoration are to:

  1. Allow for more frequent and longer duration inundation of the floodplain.
  2. Increase sediment deposition on the floodplain and reduce the amount of sediment being delivered to downstream areas.
  3. Promote aggradation in the channel to limit upstream incision and bank erosion.
  4. Provide high flow refugia for juvenile salmonids.
  5. Maintain fish passage through the reach.
  6. Increase aquifer recharge.
  7. Enhance existing channel, floodplain and wetland habitats used by a variety of native biota, including several listed species including: coho salmon, steelhead, red-legged frog and San Francisco garter snake.

The design includes the use of a variety of physical elements including several engineered log jams, a complex rock and log grade control structure, as well as several live large riparian trees that will be manipulated so they lie across the channel, while still maintaining a portion of their existing root network within the channel bank.  These elements will add roughness to the channel, limit channel capacity, and maintain the grade of the channel bed against future incision, all of which will promote more frequent and longer duration floodplain inundation and improve channel complexity.  In addition, floodplain connector channels (breaches in a berm that runs along the edge of the channel) are included in the design to further improve channel-floodplain connectivity at lower flows.

cbec’s tasks include field surveys, two-dimensional hydrodynamic modeling, scenario development and evaluation, and design calculations leading to 65% and 100% construction documents.

 

Details

Watershed: Butano Creek
Project: 15-1013