In this chapter we look into the global variation in the main processes that shape the coast: wind, waves and tides. Based on large scale observations such as the latitude and the continent, a general idea of the wave, wind and tidal conditions at a project site can be obtained. Questions that can be answered are for instance:
- What is the wind system we are dealing with at this latitude and what is the dominant direction?
- Are locally generated waves important or are we mainly dealing with swell waves?
- What wave heights can we expect?
- Does the wave climate exhibit seasonality?
- Can we expect a large tidal range in this part of the world?
- Is there a diurnal or a semi-diurnal tide?
This chapter starts with a treatment of the zonal wind systems (Sect. 4.2). Knowledge of these global wind patterns is helpful in identifying the prevailing wind conditions for a project site as well as the wave climate. In Sect. 4.3, the global wave climate is discussed and some generalisations are made about the coastal impact of different wave conditions. Subsequently, global tidal environments and coastal characteristics are discussed in Sect. 4.4. Here also it is emphasised that it is the relative effect of waves and tides rather than the absolute tidal ranges and wave heights that determines the coastal character.
Please bear in mind that wind, waves and tides vary regionally and locally as well. An example of variation due to regional geographic variation is the sheltering of the southern part of the Florida coastline from waves due to the presence of the Bahamas. On a local scale, the project location of a land reclamation may be chosen such that persistent swell cannot arrive at the site. These smaller scale variations are considered from Ch. 5 onwards.