Coastal Processes

Objectives Examine Physical Properties of Waves Examine behavioral changes of waves approaching coast Explain the role of waves in sediment erosion, transportation and deposition Discuss tides and their role in coastal erosion and deposition Discuss effects of storms and crustal movement on coastal landscapes.

Coastal Processes Shape the landscapes along the coast Impact humans Must understand processes shaping coast Impact humans More and more people moving to coast Coastal areas heavily developed Must learn to manage coastal areas Knowledge of coastal processes is management key

Waves Most important agent in shaping coastal landforms Size of waves depends on: Velocity Wind persistance Fetch Garrison, Oceanography An invitation to marine science

Wave Properties Height = vertical distance from crest to trough Wavelength = horizontal distance between successive crests or troughs Wave period = time required for two successive crests to pass a fixed point

Motion in Deep Water Waves Motion is orbital Waves with orbital particle motion termed waves of oscillation Particle motion ceases at ½ wavelength

Waves Against the Shore Swells shoal as approach coastline Feel bottom at ½ wavelength Wavelength decreases Wave height increases Wave particle motion becomes elliptical Wave breaks Swash and backwash move on beach

Wave Refraction Bending of waves as they approach coastline Part of wave in shallow area slows Part of wave in deeper area continues with higher speed Results in longshore current

Erosion of Coastal Headlands Wave refraction concentrates energy on headlands Sand accumulation occurs in lower energy bays Results in straightening of coastline

Shore Zone Currents—Rip Currents Strong narrow currents moving from beach to ocean May be identifiable through interruption of breakers and muddier sediment moving seaward

Shore Zone Currents—Longshore Currents Currents moving along the coast set up by wave refraction

Longshore Drift The movement of sediment along the shoreline by longshore currents Beach drift is movement of sediment on the beach Swash moves sand at an angle up beach Backwash swash moves sand down the beach Groins and other structures used to interrupt drift and stabilize beaches

Tides High and low tides tend to widen beaches Tidal range is greatest in estuaries, bays, and lagoons Erode and deposit sediment Erosion occurs in narrow rocky bays with great tidal ranges Where currents slow down deposition takes place

Tides

Storms May modify coastal areas in short period Storm surges plus low atmospheric pressure result in increased sea level Wave aggressively attack coastal features High tides aggravate conditions

Crustal Movements Influence development of coastal features Tectonic activity leads mostly to raising and erosion of coast California, Oregon, & Washington are examples Some coastal areas are sinking due to accumulation of sediment Texas and Louisiana are examples