Introduction to Watershed Science Marc Epstein, Instructor COASTAL PROCESSES Introduction to Watershed Science Merritt College Marc Epstein, Instructor

The edge of the sea is a strange and beautiful place The edge of the sea is a strange and beautiful place. All through the long history of Earth it has been an area of unrest where waves have broken heavily against the land, where the tides have pressed forward over the continents, receded, and then returned. For no two days is the shoreline precisely the same. Not only do the tides advance and retreat in their eventual rhythms, but the level of the sea itself is never at rest. It rises or falls as the glaciers melt or grow… Today a little more land may belong to the sea, tomorrow a little less. Always the edge of the sea remains an elusive and indefinable boundary Rachel Carson

COASTAL SYSTEM COMPONENTS Winds Weather Ocean currents Waves Climate Rocks Gravity

THE COASTAL ZONE On land - The highest water line that occurs on shore during a storm Seaward – Point at which waves can no longer move sediments on the seafloor

ESTUARIES AND THE COAST Estuary – Body of water along the coastline Open to the sea effected by tides Mix of fresh and salt water

TIDES Sea level oscillations (twice each day) Caused by gravitational influences of the sun and moon Moons influence is double that of the sun Partially enclosed waterways have greatest differences in tides

WAVES Energy moving through water Primarily caused by wind Waves are not water moving Transferring energy from molecule to molecule Water molecules move forward slightly in circular pattern

COASTAL ZONE WAVE MOTION Waves of transition – Both energy and water move forward Breakers – Wave height exceeds vertical stability Slope of shore Steep = plunging breakers Shallow = spilling breakers

LANDFORM INTERACTION Wave refraction – Results in coastal straightening Headlands – Protruding landforms of resistant rock Approaching waves focus energy around headlands Dissipate energy in coves and bays

SEDIMENT TRANSPORT AT THE SHORELINE Longshore or Littoral Current Beach Drift – Movement of particles Swash – Pushes sediment upslope Backwash – Pulls sediment downslope (undertow)

BEACH STABILIZATION Construction of groins or jetties Causes deposition up-current Causes erosion down-current

ESTUARY CLASSIFICATIONS Drowned river mouths Fjord type – glacier mouths Bar-built – barrier islands Tectonic processes – indentations from faulting

ESTUARY CIRCULATION Wind Tidal Flow River Flow Saltwater Wedge or Tidal Prism Zone of Intermixing

ESTUARY TYPES Wetland – Water dominates in soil development Lagoon – Between barrier island and mainland or shallow estuary isolated from the ocean Slough – Shallow where large areas of the bottom are exposed during low tide Salt Marsh – Protected from ocean waves

HUMAN IMPACTS ON ESTUARIES Flood Control Water Diversion Water Storage These actions change the natural flow of fresh water resulting in changes of the mixing with salt water changing the levels of salinity