Project Links
Merced River Plan Implementation: Sugar Pine Bridge Floodplain and Riverbank Restoration
Yosemite National Park » Merced River Plan Implementation: Sugar Pine Bridge Floodplain and Riverbank Restoration » Document List
This project was selected for implementation in the 2014 Record of Decision (ROD) for the Merced River Plan (MRP) Environmental Impact Statement (EIS) (PEPC 18982). This project must adhere to mitigation and stipulations in the Final EIS/Record of Decision, the MRP programmatic agreement, the CA Red-legged Frog Biological Opinion, and permit requirements. This project was categorized as a Category 1 project in the MRP programmatic agreement for Section 106.
This project will implement mitigations for leaving Sugar Pine Bridge in place. The river in the vicinity of Sugar Pine Bridge is over-widened, locally confined within its banks by riprap, and largely disconnected from its once-active floodplain. This reach of the river was examined in a multi-year study by UC Santa Barbara and other collaborators. Their final recommendation is to leave the bridge in place, implement mitigation actions in their alternative 4, and study the results.
Their preferred alternative 4 includes:
a) Floodplain reactivation (in floodplain between Reach 7 and Reach 5), with lower banks at swale entrances (within Reach 7)
b) Selective riprap removal with follow-up revegetation, within Reach 6
c) Berm removal between Ahwahnee Bridge and Sugar Pine Bridge
d) Flow-deflecting Engineered Log Jam (ELJ) at Tenaya Creek confluence
e) Floodplain-building logs (filled) with planting at specific locations within Reach 7
f) Mid-bar-forming ELJs within Reach 7
This project will address components a), b), and d). Their final report, Basis of Design, Final Report-Phase 3 (2020), is located here: https://www.nps.gov/yose/learn/nature/mercedrestoration-documents.htm
This project has two components. It will restore 20 acres of the former Lower Pines campground to natural floodplain conditions (MRP reference, Appendix E, RES-2-019). Campground construction filled overflow channels that flowed across this peninsula. These channels played an important role during flood events, alleviating flows through Sugar Pine Bridge. We will remove any remaining asphalt, excavate fill from these overflow channels to reactivate them during flooding events and decompact soils of the former roadbed and campsite footprint. Channel excavation will be a maximum depth of 2 feet which is the minimum depth that would allow for flow activation during 2-year flood events. We will restore channel topography using the 1919 USGS maps as a guide. We will manually remove conifers within the channels to allow for excavation of the channels and will remove select conifers between the channels. This will allow for the floodplain to be dominated by a mosaic of deciduous riparian species including alder, big leaf maple and cottonwood, which are currently present but crowded and shaded by a conifer overstory. To achieve floodplain restoration, we would remove select conifers <20" diameter at breast height (DBH) and up to 119 trees between 20-30" DBH, 118 trees between 31-40" DBH, 42 trees between 41-50" DBH, and 5 trees between 51-60" DBH, as time permits. Riprap south of 5 the berm between Sugar Pine and Ahwahnee bridges would be removed and replaced with native plants and willow stakes (MRP reference, Appendix E, RES-2-051).
To address river widening and low channel complexity, this project will also construct an engineered log structure upstream of Sugar Pine Bridge. This engineered log structure will mitigate effects of leaving the bridge in place (MRP reference, Appendix E, RES-2-052) and will push water toward the excavated overflow channels on the floodplain during high water events (MRP reference, Appendix E, RES-2-062). Studies have shown that the Merced River in this area has widened by ~30% since 1919. Crews will use logs generated from the floodplain restoration area and native soils. They will also plant native species such as willow, cottonwood and sedges to increase habitat quality, biodiversity and water quality. Crews will also install signage to direct the public to river access for swimming. Finally, we will install an interpretive sign on Merced River ecology and restoration.
This project will implement mitigations for leaving Sugar Pine Bridge in place. The river in the vicinity of Sugar Pine Bridge is over-widened, locally confined within its banks by riprap, and largely disconnected from its once-active floodplain. This reach of the river was examined in a multi-year study by UC Santa Barbara and other collaborators. Their final recommendation is to leave the bridge in place, implement mitigation actions in their alternative 4, and study the results.
Their preferred alternative 4 includes:
a) Floodplain reactivation (in floodplain between Reach 7 and Reach 5), with lower banks at swale entrances (within Reach 7)
b) Selective riprap removal with follow-up revegetation, within Reach 6
c) Berm removal between Ahwahnee Bridge and Sugar Pine Bridge
d) Flow-deflecting Engineered Log Jam (ELJ) at Tenaya Creek confluence
e) Floodplain-building logs (filled) with planting at specific locations within Reach 7
f) Mid-bar-forming ELJs within Reach 7
This project will address components a), b), and d). Their final report, Basis of Design, Final Report-Phase 3 (2020), is located here: https://www.nps.gov/yose/learn/nature/mercedrestoration-documents.htm
This project has two components. It will restore 20 acres of the former Lower Pines campground to natural floodplain conditions (MRP reference, Appendix E, RES-2-019). Campground construction filled overflow channels that flowed across this peninsula. These channels played an important role during flood events, alleviating flows through Sugar Pine Bridge. We will remove any remaining asphalt, excavate fill from these overflow channels to reactivate them during flooding events and decompact soils of the former roadbed and campsite footprint. Channel excavation will be a maximum depth of 2 feet which is the minimum depth that would allow for flow activation during 2-year flood events. We will restore channel topography using the 1919 USGS maps as a guide. We will manually remove conifers within the channels to allow for excavation of the channels and will remove select conifers between the channels. This will allow for the floodplain to be dominated by a mosaic of deciduous riparian species including alder, big leaf maple and cottonwood, which are currently present but crowded and shaded by a conifer overstory. To achieve floodplain restoration, we would remove select conifers <20" diameter at breast height (DBH) and up to 119 trees between 20-30" DBH, 118 trees between 31-40" DBH, 42 trees between 41-50" DBH, and 5 trees between 51-60" DBH, as time permits. Riprap south of 5 the berm between Sugar Pine and Ahwahnee bridges would be removed and replaced with native plants and willow stakes (MRP reference, Appendix E, RES-2-051).
To address river widening and low channel complexity, this project will also construct an engineered log structure upstream of Sugar Pine Bridge. This engineered log structure will mitigate effects of leaving the bridge in place (MRP reference, Appendix E, RES-2-052) and will push water toward the excavated overflow channels on the floodplain during high water events (MRP reference, Appendix E, RES-2-062). Studies have shown that the Merced River in this area has widened by ~30% since 1919. Crews will use logs generated from the floodplain restoration area and native soils. They will also plant native species such as willow, cottonwood and sedges to increase habitat quality, biodiversity and water quality. Crews will also install signage to direct the public to river access for swimming. Finally, we will install an interpretive sign on Merced River ecology and restoration.