Henderson, R. and Beamer, E., 2015. Fisher Slough Floodgate Report for Water Year 2014. Skagit River System Cooperative, La Conner, WA. pp. 37.

This report describes floodgate monitoring efforts for the Fisher Slough floodgate, located in the South Fork Skagit River tidal delta. Monitoring results relate to measurements of floodgate door openness, water depth, water surface elevation, and floodgate operation for Water Year 2014 (WY2014), the period of October 1, 2013 through September 30, 2014. The floodgate was originally installed to provide flood protection from Skagit River floods to the Fisher Slough basin. In 2009, old barn-style doors were replaced with a self-regulating floodgate designed to improve fish passage and tidal exchange through the gates while still maintaining flood protection. Per an agreement with The Nature Conservancy the water velocity criterion was not evaluated this year.
We compare monitoring results to floodgate operational criteria that were established based on fish passage and flood protection needs. We also discuss monitoring results and criteria in order to provide information useful to adaptively manage the Fisher Slough floodgate, if necessary, to achieve and balance its multiple objectives of fish passage, flood protection, drainage, and irrigation.
Monitoring equipment used to collect water surface elevation (WSE) and floodgate door openness data, retrofitted with new data loggers at the start of WY2014 were shown to collect results accurately for WSE.
Fisher Slough floodgate operation did not meet all management criteria during WY2014. During the Fall/Winter Flood Control Period the criterion that the floodgate doors be set to close at elevation of 7.5 ft NAVD88 was met and doors opened at least once per day to allow adult spawner (i.e. salmon heading upstream to spawn) passage. However, the doors did close at water elevations less than 7.5 ft NAVD88. During the Spring Juvenile Chinook Migration Period, floodgate doors were set to close at 9.5 ft NAVD88, but the floodgate doors did close at water elevations below 9.5 ft NAVD88 and were open 78.9% of the time rather than the required 90% or more. Also during spring, the criterion that water depth be at least 0.5 feet (0.15 meters) deep for more than 10% of the time across the floodgate sill was met in WY2014; water depth was greater than 0.5 feet over the sill 100% of the period. During the Summer Irrigation Period the floodgates were lashed open as required except for a few days when the doors were closed to facilitate upstream work.