6. Conclusions

This chapter has strived to summarize the salient features of a suite of past studies [7–11] that have analyzed the issue of changing tidal evolution that is correlated with MSL variability, both of which are likely related to climate-change related factors. It has been demonstrated that these tidal changes are likely to have the greatest effect on coastal locations, especially estuarine regions, which are often highly developed, densely populated, and environmentally sensitive. Overall, in both the Pacific and Atlantic, over 90% of all locations surveyed show a significant TAC in at least one tidal constituent, and around one-third of all locations have a significant δ-HAT.

In general, coastal inundation is associated with peak water level, not mean sea level, and depends on the combined effects of tides, storm surge, sea-level variability, inland precipitation, river flow, and other factors which may lead to increases in extreme water level exceedance probabilities. MSL rise can affect the tidal dynamics directly, or the reasons for the observed changes can be related to secondary mechanisms, including, but not limited to: river flow, changing bed friction due to harbor development and other causes, barotropic friction effects, heat content, buoyancy, stratification, mixing and eddy viscosity, ocean currents, waves, storm surge, and indeed, any source of water or energy input.

Here, the effects of tidal evolution, and the impacts of these changes on nuisance flooding have been described. Identifying connections and correlations between tidal range and MSL is critical for making reliable predictions of coastal water levels and inundation risk. When combined with storm surge, larger tides and higher MSL may amplify flood risk, coastal inundation, damage to infrastructure, and population displacement. Even without the consideration of storm surge, changes in tides and sea-levels may lead to more occurrences of nuisance flooding.
