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Project Description:
Spanish Creek: The project would restore Spanish Creek in
Meadow Valley at Spanish Ranch. Spanish Creek in Meadow Valley has
been historically manipulated and channelized. It has subsequently
degraded. Spanish Ranch Road (County Road 413) forces Spanish Creek
to flow under a 43-foot wide bridge, which reduces the stream
channel-floodplain width by 90%. The constriction is an effective
barrier to high flows, causing it to slow and a large backwater area
to form. Bedload material quickly deposits within this backwater
area, creating large gravel bars that force flows against the
opposite, eroding channel banks. The long-term result is the loss
of property and a migration of the stream channel around the
bridge. Project work would remain within the entrenchment and would
involve a variety of treatments. The proposed treatments include:
1. inserting 12 culverts into the south approach to the
bridge to alleviate pressure on the bridge, spread flood flows out
onto 100 feet of floodplain, alleviate the backwater effect, and
reduce upstream bank erosion and the potential for the stream to
“end-run” the bridge. 2. Treat 200 feet of eroding outcurve
channel bank with boulder vanes, sloped bank, and transplanted
vegetation. 3. Remove 1200 cubic yards of gravel berms used
to further constrict and direct stream flows within a 2300 foot long
section of channel-floodplain upstream of the bridge, opening the
section up for improved overbank flows and reducing concentration of
flows against the entrenchment banks. |
