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Introduction
The experiment is conducted at Sand City, California where the beach is composed of a steep beach face, crescentic bars intercepted by rip channels (Figure 1).
Steep Beach Objectives: Our objectives are to measure wave transformation and set-up/down, breaking wave and current-induced turbulent bottom and surface boundary layers, and sediment flux in the surf zone. It is hypothesized that the plunging and collapsing/surging wave breaking processes occurring on a steep beach are significantly different than plunging/spilling breaking wave processes previously measured at Duck over a moderately sloping bar. Plunging breakers inject bubbles and turbulence deeper into the water column, sometimes penetrating to the bottom and suspending the sediments. Wave reflection can be significant on steeper beaches, and it is hypothesized that the breaking wave location is modified by reflected waves owing to modulation of the water depth and the kinematics in the breaking wave. The modulation of the breaker location can then modify the dynamics of the nearshore.
Measurement objectives include utilizing fixed arrays of new high resolution instruments to measure the surface and bottom boundary layers, suspended sediments in 3-dimensions and bottom morphology under breaking waves. An array of pressure sensors, PUV and ADV systems will measure cross-shore gradients of waves, velocity, set-up and suspended sediments, and an alongshore array will measure shear instabilities of longshore currents and infragravity waves.
Measurements include a cross-shore array of 8 pressure sensors, 2 PUVs, 3 Sontek ADV Hydra systems (3 components of velocity, suspended sediments, waves and bottom elevation) and the BCDV2, and an alongshore lagged array of 5 PUVs (Figures 2 and 4). A fixed central array will be deployed (Figure 3), including vertical arrays of 8 em's and 12 conductivity cells, and a x-y scanning altimeter, a co-located surface piercing wave staff and pressure sensor, along with the new high resolution velocity, sediment and morphology instruments.
Additional measurements may include scanned LIDAR from a 10 m tower located in the surf zone, and an upward looking BCDV2 at central array.
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