Snohomish Railroad Grade Beach Nourishment

Efforts

Efforts describe the goal-oriented activites of workgroups

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This effort in the Carkeek to Everett Beach System nourished beaches by placing clean sediment at designated areas along the shore, and removed armoring at Howarth Park in the City of Everett. The effort has been monitored to evaluate the effects of beach nourishment actions along the Burlington Northern-Santa Fe railroad grade.

• Habitat Work Schedule
• PRISM Project Webpage for ESRP

Objectives

• Improve the quantity of potential forage fish habitat along the project reach,
• Initially supply over 18,000 C.Y. of finer sediments (coarse sand and fine gravel) to the system,
• Retain finer sediments in the upper intertidal (+5 MLLW to MHHW) over a reasonable time frame,
• Provide delivery of gravel to adjacent shorelines,
• Increase backshore width to encourage growth of riparian vegetation,
• Remove riprap armoring,
• Minimize adverse effects to key biological communities (particularly eelgrass), and
• Enhance nearshore rearing habitat conditions for juvenile salmonids.

Monitoring

The University of Washington and Snohomish County surveyed target sites along the Burlington Northern Santa Fe (BNSF) railroad grade before placement of new sediment and removal of armoring in summer 2016. The Snohomish County Beach Nourishment Project (SCBNP) is an ESRP portfolio project constructed in 2016. This project uses the SCBNP as the centerpiece of a monitoring effort to assess the functional success of nourishment and other treatments. Detailed beach monitoring has been conducted both within the beach nourishment region and south of the region, where no nourishment has been done. In each region, four armored sites along the railroad and four reference sites with more natural shoreforms and vegetated beach characteristics in front of the railroad have been studied. Changes among years at the non-nourished sites have been compared to changes within the nourished region to help evaluate the short- and long-term effects of sediment addition on numerous shoreline functional responses.

Extensive sampling was conducted in 2016 (pre-nourishment, and pre-armor removal at Howarth Park). Post-nourishment sampling was conducted in 2017-2019. Transect-based surveys and photographs have been used to collect data on:

• Beach wrack and riparian cover and composition.
• Upper-shore invertebrate populations (crustaceans and insects, primarily).
• Beach topography, zonal widths and substrate size.
• Benthic infauna at Mean Low Water.
• Forage fish spawning events.

The full study and conclusions of the project are summarized in a final report. Overall, the study found that sediment nourishment along the BNSF railroad can improve some structural and functional aspects of shorelines, but these improvements are unlikely to persist for longer than a few years if they are limited in scale or solely rely on re-use of finer, clean dredged material. Longer term monitoring may be needed to adequately assess these situations, likely along with continued experimental nourishment interventions and maintenance.

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• Project Narrative Proposal
• Budget Worksheet

particles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment.

mean higher high water