SAN LORENZO LAGOON HOW DOES IT WORK 2016

CONCEPTUAL LAGOON FUNCTION LAGOON a stretch of salt water separated from the sea by

OPEN MOUTH - TIDAL 10 feet Time Elapsed ~ 1 hour

LAGOON WATER LEVELS • Stream Flow • Beach Condition • Width • Sediment Size

SALINITY Amount of salt in the water • Salt Water is heavier than freshwater

2002 - 2012 Water Quality Data from 2 nd Nature, Wave Data from ESA

HOW DOES IT WORK • Waves strongly influence water level and salinity in closed

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SAN LORENZO LAGOON: HOW DOES IT WORK? 2016 State of the San Lorenzo River Symposium Dr. David Revell revellcoastal@gmail. com 5/21/2016

CONCEPTUAL LAGOON FUNCTION LAGOON a stretch of salt water separated from the sea by a low sand bank (or coral reef) Closed Mouth – Lagoon Full Open Mouth – Tidal Conditions Open Mouth – Perched (muted tides) Figure from ESA PWA Closed Mouth

WAVE OVERTOPPING

OPEN MOUTH - TIDAL 10 feet Time Elapsed ~ 1 hour

OPEN MOUTH - STREAM

CLOSED MOUTH

7. 0’ NGVD 10/30/2014 9/25/2014

LAGOON WATER LEVELS • Stream Flow • Beach Condition • Width • Sediment Size • Lagoon Mouth • Inlet dimensions • Depth of sill • Ocean Water Levels • Tides • Sea level rise • Storm Surge & Wave Run-up • Channel Maintenance • Human activities 8

SALINITY Amount of salt in the water • Salt Water is heavier than freshwater • Salt water sinks and freshwater floats • Creates different types of habitat conditions DISSOLVED OXYGEN (DO) Amount of oxygen in the water • Needed by fish and other aquatic organisms • Without oxygen aquatic organisms suffocate

2002 - 2012 Water Quality Data from 2 nd Nature, Wave Data from ESA PWA

HIGH STREAM FLOW

LOW STREAM FLOW

NO STREAM FLOW

IMPACT OF THE HARBOR

SEABRIGHT BEACH FILLING

SEABRIGHT BEACH 1955

1953 SEABRIGHT BEACH

MARCH 2012

08/29/2014

09/08/2014

11/10/2014

11/12/2014

11/18/2014

11/19/2014

11/21/2014

11/22/2014

11/23/2014

11/29/2014

12/03/2014

12/04/2014

12/05/2014

12/06/2014

12/08/2014

12/11/2014

12/12/2014

12/22/2014

Close-up: 2007 Low Waves

Close-up: 2005 High Waves

HOW DOES IT WORK • Waves strongly influence water level and salinity in closed lagoon • Beach sill typically mutes tide below 0 -3’ NGVD • Bottom temperature high until lagoon freshens • Lagoon does freshen some during closure (2 - 4 weeks) • Bottom DO generally low after mouth closure • Wave overwash increases DO at bottom Beach elevation ranges from 6. 5 to 9’ (NGVD) during closure Beach crest is highest in front of the inlet Thalweg depth varies widely from beach to train trestle Everything will change in the future

SEA LEVEL RISE