Understanding how ENSO modifies coastal hydrodynamics is in its infancy. Ten episodes of large-scale channel migration occurred at the entrance to Willapa Bay, Washington, over the last 148 years. Ebb shoal breaching terminated each cycle during an El Nino. How El Ninos could trigger shoal breaching is not known. Long-term trends and typical seasonal cycles in 44 hydrodynamic parameters are determined in order to define their monthly anomalies.
All parameters show strong seasonal variations.
Of all the parameters, sea level shows the strongest long-term trend and the best correlation with El Nino. Sea level tends to be unusually high during El Ninos and low during La Ninas. Even in the Columbia River Estuary, water level anomalies show an ENSO response. Runoff into the small neighboring Willapa basin does not vary with ENSO phases. Ocean wave energy increases during El Nino, but not detectably during La Nina.