Field observations of wave runup on a sand beach.
Hoernemann, Michael John.
Thompson, Warren C.
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Six sets of field measurements of runup resulting from both wind waves and swell were made on a uniform sand beach. Waves were recorded simultaneously directly offshore at a point outside the surf zone. Each individual runup was correlated with a specific wave, using a traveltime plot. Runup occurrences were always found to be fewer in number than wave occurrences, particularly when wind waves were present. Large variations in the runup resulting from waves of a given height were found to exist. These variations in height and ratio of runup to waves were caused in large part by the interaction of successive foam lines. Interaction occurred in the form of retardation by backwash of preceding waves, overtaking by a following foam line, and overriding by a small unbroken wave. It is concluded that the complicated nature of runup resulting from ordinary sea and swell makes it difficult to predict runup accurately from laboratory studies.