Ocean waves that grow especially tall a few times during the year, rumbling against the California coast and offering a glimpse into future sea level rise and a reshaping shoreline, according to state coastal regulators.

Those tides rolled up to San Onofre last weekend, where a sea wall stands to protect what nearby communities fear is a man-made disaster in waiting: the decommissioned but still radioactive San Onofre Nuclear Generating Station (SONGS).