Comparison between the skew surge and residual water level along the coastline of China

Abstract A better understanding of the storm surge phenomenon is essential for coastal protection, future planning, and coastal ecosystem conservation. Using hourly sea level data from 15 tide gauges along the coastline of China the metrics, skew surge and residual water level, which are used to represent storm surges, are compared in this study. The relationship between residual water level, skew surge and predicted high tide were analyzed using two statistical measurements. The results showed that unlike the annual maximum residual water level, the annual maximum skew surge and the astronomical high tide tended to coincide more frequently (more than 50% of the annual maximum skew surges occurred at high tide). Thus, the skew surge was more suitable than the residual water level for use in risk-based coastal planning frameworks. Using the monthly maximum value and indices of the storm surge (storm surge number, duration and intensity), we compared the performances of skew surge and residual water level in expressing changes of storm surges. These two metrics can both capture changes in storm surge activities on seasonal, decadal and long-term scales, and correlation coefficients of storm surge intensity between residual water level and skew surge were greater than 0.80 at 11 tide gauges. At most tide gauges, the skew surge was significantly correlated with 4-5 nearby tide gauges while the residual water level was correlated with only 1-2 tide gauges, the skew surge may be a better metric for risk-based coastal planning frameworks if the interpolation method is used. The El Nino-Southern Oscillation (ENSO) can affect the storm surge frequency along the coastline of China. The effects of the ENSO were more obvious when the residual water level was selected. In conclusion, the skew surge can be selected for use in risk-based coastal planning frameworks, while the residual water level may be a better metric for capturing the relationship between storm surges and climate changes.