Data from: Estimates of extreme and low frequency reef-flat water levels at Ipan, Guam from offshore waves

This collection provides the reef face and shoreline bulk statistics and time series at Ipan, Guam used in Becker and Merrifield 2026.

Abstract: Wave and water level observations collected at a shore-attached fringing reef at Ipan, Guam are used to related offshore wave conditions and reef water levels to extreme water levels near the shoreline (2% exceedance, ŋ₂). The observations capture conditions during three extreme storm events, including Typhoon Dophin that caused coastal flooding at Guam. For the dissipative reef at Ipan, the wave setup and low frequency (LF) waves are the dominant contributions to ŋ₂ over the entire data set. A new parameterization of ŋ₂ for Ipan is developed using back-refracted significant wave height and wavelength, H₀ and L₀, and the reef-flat water depth h_r. The setup is highly correlated with H₀, and the reef flat wave motions with h_r sqrt(H₀L₀). Waves with longer incident periods provide stronger forcing for low frequency waves on the reef flat. Coastal flooding during Dolphin was due in part to near-shoreline LF significant wave heights reaching 1.3m, twice as large compared to a previous storm event with similar offshore wave heights but shorter wave period. Estimates of the 2% exceedance near-shoreline total water level, h_2%, that include the tide, nontidal residuals and the wave-driven ŋ₂ are highly correlated with those obtained directly from shoreline pressure observations over the range of conditions observed. The parameterization of ŋ₂ from offshore waves and reef flat near-shoreline water levels may be relevant for assessing storm-driven flood risk at dissipative reefs of similar character.