Unit 7
Waves & Beaches
Topic 1 Watching Waves

Surf zone is the area near shore where waves break.

How far from shore a wave breaks depends on the
length of the wave and the depth of the water.
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How a wave breaks depends on the:
– steepness of the bottom slope
– whether the slope is smooth or irregular
– whether the bottom is composed of shifting sand or solid rock

Waves may break more than once as they come
to shore.

Each time it breaks, it gives up energy and
becomes smaller and shorter.
Types of Breaking Waves

Plunging waves
– Occurs when the swell comes
out of deep water and hits a
shallow sandbar or reef.
– Form where there is a
moderately steep, sloping
bottom.
– Form tubes or curls that cascade
water in a circular motion
downward into the trough and
break forcefully with a rapid
release of energy.
– If the bottom is very steep, the
top of the wave may break over
the lower half forming a
Collapsing wave with no curl.
Ultimately, these are the
waves that surfers look for.
They break top to bottom
and tend to be faster and
more challenging.

Spilling breakers
– They form where the bottom slopes gradually.
– These waves advance to shore with a line of
foam down their front.
– They break slowly over long distances
– The wave energy is gradually released over time
and the beach.
– This type of surf is best for landing craft.
Break slowly
Break rapidly

Surging breakers
– Steep beach slope
– They form when large waves
suddenly hit bottom in shallow
water.
– Wave does not break - surges up to beach

Example: Tsunami and tidal bores(occurs where a river empties
into an ocean/sea. A tidal bore is a strong tide that pushes up the
river, against the current. They are true tidal waves. A tidal bore
creates a surge or a sudden change in depth.
– which look like walls of water advancing toward shore.