1. Field Trip Issues
Tues. 8am – WM loading dock
2 vans
Bring Lunch
Bring something to take field notes with
Bring wet-able footwear and appropriate clothing – perhaps a change of clothing?
I will you before Tuesday with your group assignments for the trip

2. Questions on Waves Problem Set Assignment?

3. Berm Formation
What's the berm? The nearly horizontal portion of the exposed beach.
Berm elevation coincides with wave runup height (Bagnold, 1940)
Takeda and Sunamura (1982) related berm elevation to wave conditions
Bascom's (1953) explanation of berm formation:
"After a wave breaks, the water rushes forward up the beach face, carrying sand with it, losing velocity as it goes because it is opposed by gravity and friction and because of water losses through percolation. As the beach builds seaward, it leaves a nearly horizontal berm that corresponds to the elevation to which sand had been carried by the swash runup.”

4. Berm Formation
Uniformity of wave height and rapid berm growth allows the berm elevation to reflect tidal variations (Strahler, 1966).
Large waves bring sediment over the crest and deposit atop the berm -- can produce landward sloping berm if crest grows seaward.
High storm waves cut back and destroy the berm, but under certain conditions are the agents responsible for sediment delivery high on the beach, hence can cause the berm to grow -- an interesting paradox worthy of a simple numerical model.
A storm may leave a high "marker" berm, and if progradation is rapid enough, a beach may display a series of abandoned storm berms -- documenting the storm history witnessed at that site.

5. Longshore Bars and Troughs
Sediment packages parallel to shore, that “store” beach sediment
Can be up to 50 km in longshore extent – Lake Michigan example
Can be segmented by gaps that allow rip currents to flow through
Quite effective in decreasing assailing wave energy – acts as a natural breakwater
Bar position is influenced by wave conditions Keulegan (1948) found, in a laboratory channel, that as H increases, bar moves offshore and as T decreases, bar moves onshore
Typically thought to form via the “breakpoint hypothesis”

6. Longshore Bars and Troughs
Larson, Kraus, and Sunamura (1988) compiled lab wave channel data to document bar volume increase with time
Approach an equilibrium value for each of the wave conditions shown.

7. Troughs associated with longshore bars
Troughs are formed by the turbulence associated with the bar –induced wave breaking (Miller, 1976)
Sunamura (1985, 1989) developed a relationship between trough position and wave conditions

8. Multiple Bar Systems
Multiple bars/troughs may form from multiple breaker zones
As waves break initially, then reform within the surf zone, another bar/trough may develop

9. Bar Migration and Welding
Inner bar can show great variability
During onshore movement, bar height increases and trough is constricted
Eventual welding onto the beach foreshore
Primary means of “recovery” after a storm moves upper beach material offshore and performs the “flattening”

10. Alternative to Breakpoint Hypothesis – Standing Waves
Reflection of periodic surface waves sets up a series of standing waves that create a unique orbital pattern
Sediment scour beneath nodes and accumulation beneath antinodes

11. Profile Changes due to Storms
notes

12. Shepard Data Set

13. Bascom’s Data

14. Accretion vs. Erosion Dominated Intervals