Abstract Title

Session S-06H: Puget Sound Shorelines and the Impacts of Armoring: State of the Science 2014

Keywords

Shorelines

Start Date

1-5-2014 1:30 PM

End Date

1-5-2014 3:00 PM

Description

Protection programs are not holding the line against the incremental impacts of shoreline development. Habitat of the beach-spawning surf smelt (Hypomesus pretiosus), a forage fish critical to marine food webs, is vulnerable to the impacts of armoring and sea level rise (Simenstad et al 1979, Thom et al 1994, Krueger et al 2009). Scientists in San Juan County, Washington recently completed research on the tidal distribution of surf smelt eggs; the cumulative impacts of armoring on forage fish spawning habitat; and sea level rise vulnerability. To determine the tidal distribution of surf smelt eggs, samples were collected at 26 transects across the vertical beach profile of active spawn events in five regions of the County. Results show that 35% of incubating surf smelt eggs are located above Mean Higher High Water. ArcGIS was used to evaluate the cumulative impacts of armoring on forage fish spawning habitat, including direct burial, indirect impacts such as disruptions to sediment processes and shoreline development patterns. Findings show that shoreline armoring buries just over 10 acres of known surf smelt spawning habitat in the County. Armored feeder bluffs and armor located below mean sea level occur in drift cells with known surf smelt spawning habitat, disrupting sediment supply and transport. A strong relationship between residential home setback distances and the likelihood of armoring was also documented; 74% of armored sites have a house located closer than 100 feet from the marine shoreline. Sea level rise vulnerability models were applied across moderate and high projection scenarios and two planning horizons (2050 and 2100). Results indicate that forage fish spawning beaches will likely be threatened by sea level rise in the short term, especially at the 16% of sites where existing armor will constrain the landward translation of upper beach habitat (Griggs et al 1994, Krueger et al 2009). Results have implications for improved management of shorelines across the Salish Sea, including both protection and restoration strategies.

Share

COinS
 
May 1st, 1:30 PM May 1st, 3:00 PM

The Cumulative Impacts of Shoreline Armoring on Forage Fish Spawning Habitat in San Juan County, Washington

Room 607

Protection programs are not holding the line against the incremental impacts of shoreline development. Habitat of the beach-spawning surf smelt (Hypomesus pretiosus), a forage fish critical to marine food webs, is vulnerable to the impacts of armoring and sea level rise (Simenstad et al 1979, Thom et al 1994, Krueger et al 2009). Scientists in San Juan County, Washington recently completed research on the tidal distribution of surf smelt eggs; the cumulative impacts of armoring on forage fish spawning habitat; and sea level rise vulnerability. To determine the tidal distribution of surf smelt eggs, samples were collected at 26 transects across the vertical beach profile of active spawn events in five regions of the County. Results show that 35% of incubating surf smelt eggs are located above Mean Higher High Water. ArcGIS was used to evaluate the cumulative impacts of armoring on forage fish spawning habitat, including direct burial, indirect impacts such as disruptions to sediment processes and shoreline development patterns. Findings show that shoreline armoring buries just over 10 acres of known surf smelt spawning habitat in the County. Armored feeder bluffs and armor located below mean sea level occur in drift cells with known surf smelt spawning habitat, disrupting sediment supply and transport. A strong relationship between residential home setback distances and the likelihood of armoring was also documented; 74% of armored sites have a house located closer than 100 feet from the marine shoreline. Sea level rise vulnerability models were applied across moderate and high projection scenarios and two planning horizons (2050 and 2100). Results indicate that forage fish spawning beaches will likely be threatened by sea level rise in the short term, especially at the 16% of sites where existing armor will constrain the landward translation of upper beach habitat (Griggs et al 1994, Krueger et al 2009). Results have implications for improved management of shorelines across the Salish Sea, including both protection and restoration strategies.