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

2. 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

3. COASTAL SYSTEM COMPONENTS
Winds
Weather
Ocean currents
Waves
Climate
Rocks
Gravity

4. 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

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

6. 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

7. 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

8. 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

9. 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

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

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

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

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

14. 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

15. 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